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  • The use of titanium dioxide nanotubes as photoanodes for chloride oxidation
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-24
    Con Boyle; Nathan Skillen; H.Q. Nimal Gunaratne; Preetam K. Sharma; J. Anthony Byrne; Peter K.J. Robertson

    In recent years, significant attention has been given to the development of photoelectrochemical materials capable of producing high current densities under illumination for a range of applications. Titanium dioxide nanotubes (TiNTs) have emerged as a favourable nanomaterial due to a reduced rate of recombination coupled with the ability to generate stable and high photocurrents. To date however, there have been no reports on the use of TiNTs for the photoelectrochemical production of chlorine, a powerful disinfectant, under UV light. The work reported here describes the construction of TiNTs for chlorine generation under low power UV-Light Emitting Diode (UV-LED) irradiation. Linear sweep voltammetry has shown TiNTs to be active for chlorine generation, achieving an average faradaic yield of ~60%, which was found to be significantly higher when compared to sol-gel electrodes (~40%). Furthermore, the impact of electrode conditioning was evaluated, demonstrating improved performance after removing surface contaminants.

    更新日期:2020-01-24
  • Combing oxygen vacancies on TiO2 nanorod arrays with g-C3N4 nanosheets for enhancing photoelectrochemical degradation of phenol
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-24
    Fan Qi; Weijia An; Huan Wang; Jinshan Hu; Hongxia Guo; Li Liu; Wenquan Cui

    We reported a novel TiO2-x/g-C3N4 nanorod arrays photoelectrode by urea drop-calcined and NaBH4 reduction. Due to synergistic effect of the oxygen vacancies and the g-C3N4 nanosheets, the TiO2-x/g-C3N4 photoelectrode exhibited excellent photoelectrochemical property and photoelectrocatalytic activity. The photocurrent density of TiO2-x/g-C3N4 was 6-fold and 1.5-fold higher than TiO2 and TiO2/g-C3N4, respectively. Meanwhile, the phenol degradation rate of TiO2-x/g-C3N4 photoelectrodes was as high as 83% under the stimulated solar light. Besides, the oxygen vacancies could promote the formation of the Z-scheme heterojunction between the TiO2 nanorods and g-C3N4 nanosheets.

    更新日期:2020-01-24
  • BDC-Zn MOF sensitization by MO/MB adsorption for photocatalytic hydrogen evolution under solar light
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-21
    Luis Ángel Alfonso Herrera; Paola Karen Camarillo Reyes; Ali M. Huerta Flores; Leticia Torres Martínez; José María Rivera Villanueva

    In this work, a new semicrystalline MOF synthesized from terephthalic acid and zinc nitrate is described, as well as an integral characterization of its physicochemical properties. BDC-Zn was evaluated in three applications: Methyl orange (MO) and Methyl Blue (MO) adsorption/photocatalytic degradation and H2 evolution. MO presents the best adsorption result; with a maximum adsorption capacity of 2100 mg/g, which is higher than all the MOF's reported in the literature. For H2 evolution, the activity was enhanced 24 times in photocatalyst with MO adsorbed, and 27 times for the MB adsorbed (from 47 to 1148 and 1259 μmol/gh, respectively). This result is attributed to better light adsorption and a decrease in charge recombination.

    更新日期:2020-01-22
  • Management of losses (thermalization-transmission) in the Si-QDs inside 3C–SiC to design an ultra-high-efficiency solar cell
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-21
    Hamid Heidarzadeh; Ali Rostami; Mahboubeh Dolatyari

    Thermalization loss is one of the major losses in the single junction solar cells. Here, 3C–SiC as a wide bandgap semiconductor is used to manage this loss. To prevent the transmission of low energy photons, the intermediate bands inside the forbidden band gap is used. To do this, silicon quantum dots inside silicon carbide is suggested. At first, the detailed balance calculations are carried out to determine the efficiency limits of a cell with one and two mini-bands. Optical simulation using 3D FEM solution of the Schrodinger equation is done to obtain mini-bands, wave functions, and hence the optical absorption coefficient. Dimension parameters of a QD array like radius, inter-dot spacing, and array size are optimized to obtain a maximum efficiency. Inter-band and inter-sub-band absorption coefficient are calculated. That applied to determine the optimum characteristic of a QD–based intermediate band solar cell. The photocurrent increases as the inter-dot spaces decrease. Suitable radiuses and inter-dot spaces are found to obtain a high absorption coefficient and hence higher photocurrent. Finally, the effect of non-radiative recombination on the device performances is simulated. These results provide significant information to design a three-dimensional QDs based intermediate band solar cells.

    更新日期:2020-01-22
  • Study of the effects of NaCl or NaOH as sodium dopant precursors in p-type nanocrystalline Cu2O thin films
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-14
    L. Hill-Pastor; T. Díaz-Becerril; R. Romano-Trujillo; M. Galván-Arellano; R. Peña-Sierra

    The effects of sodium chloride (NaCl) or sodium hydroxide (NaOH) used to control the p-type conductivity of cuprous oxide Cu2O thin films by reactive thermal annealing (ReTA) at 550 °C in low oxygen content applied to NaX/Cu2O (X = Cl or OH) bilayers were studied. NaX nanolayers were deposited by dipping the Cu2O films in their saturated solutions. It has been reported that annealing Cu2O films covered with NaCl powders increased their hole concentration, but the effects of the X− ions on the oxide film had not been clarified. Here we report that the ReTA process applied to NaX/Cu2O bilayers reduces the electrical resistivity and increases the hole mobility, but the surface characteristics were also modified. During the ReTA process, CuXn (n = 1, 2) chemically reactive compounds are produced etching the film surface. The resistivity of the films was reduced by a factor of ten with respect to the as-grown Cu2O films by the Na incorporation and the hole mobility increased by the surface passivation due to the CuXn surfactant compounds produced during the ReTA process. The ReTA process applied during short periods the Cu2O phase was also stabilized according to the experimental results.

    更新日期:2020-01-21
  • The influence of cobalt (Co) doping on the electrical and dielectric properties of LaCr1-xCoxO3 perovskite-oxide compounds
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-20
    M. Coskun; O. Polat; F.M. Coskun; Z. Durmus; M. Caglar; A. Turut

    We synthesized LaCr1-xCoxO3 (x = 0, 0.01, 0.10, 0.15, 0.20, 0.30) compounds by solid-state reaction method. SEM and EDX analyses were carried out to study their structural and chemical properties. Furthermore, their electrical/dielectric properties including real and imaginary part of dielectric function, real and imaginary part of impedance, conductivity, were investigated at wide temperature (between −100 0C and 100 0C) and frequency range (1 Hz–107 Hz) by using Broadband Impedance Spectroscopy (Novocontrol). Temperature dependent power law exponent, s, showed that different conduction mechanisms need to be considered to study the conduction in the investigated samples. The calculated activation energies from the conductivity varied between 0.170 eV and 0.388 eV indicating that the oxygen vacancies and small polaron hopping conduction taken place in the samples. Moreover, the Nyquist plots demonstrated that grain and grain boundary relaxations happen in the investigated specimens.

    更新日期:2020-01-21
  • Mobility improvement of Zn1-xMgxO:Al prepared under room temperature by co-sputtering through optimizations of Al and Mg contents
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-20
    Jakapan Chantana; Yuya Ishino; Yu Kawano; Takahito Nishimura; Takashi Minemoto

    ZnO:Al (AZO) and (Zn,Mg)O:Al (AZMO) films with several Al and Mg contents were deposited by radio frequency co-sputtering process under a room temperature (25 °C). The effects of Al and Mg contents on optical and electrical properties of the AZO and AZMO films were investigated for the suitability of the transparent conductive oxide (TCO) application in optoelectronic devices, requiring low resistivity and high transparency through the enhanced mobility. It is determined that Hall mobility of the AZO is increased, and its carrier concentration is decreased with an almost constant resistivity under the decreased Al content from about 1.7 to 0.3 at.%. The AZO film with the decreased Al content to about 0.6 at.% possesses the enhanced Hall mobility to 32.1 cm2/Vs and the reduced free-carrier absorption, which is suitable for the TCO application with its low resistivity of 5.6 × 10−4 Ω cm. It is also noted that optical bandgap energy (Eg) of the AZO films is increased with the increased Al content due to a Burstein-Moss shift. Moreover, the Mg addition into the AZMO films yields the increase in their Eg and the decrease in the free-carrier absorption under the same Al content. The resistivity of about 2.5 × 10−3 Ω cm by enhancing Hall mobility is consequently obtained in the AZMO films with the Mg content range of 0.06–0.10 with the decreased free-carrier absorption for the TCO application.

    更新日期:2020-01-21
  • Transparent p-type NiO:Al thin films as room temperature hydrogen and methane gas sensors
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-14
    E. Gagaoudakis; G. Michail; D. Katerinopoulou; K. Moschovis; E. Iliopoulos; G. Kiriakidis; V. Binas; E. Aperathitis

    Transparent Al-doped NiO thin films with thickness of 100 nm were prepared by radio frequency (rf) sputtering technique in order to investigate their response to reducing gases such as hydrogen (H2) and methane (CH4), at room temperature (RT). During deposition, the amount of doping [Al/(Al + Ni)] was 10%, while the O2 content in the Ar–O2 mixture in the plasma was 2.8%. These optimum values were set to obtain films with transmittance over 40% in the visible and optical energy band gap (Eg) of 3.65 eV. All films were polycrystalline, with a crystallite size of 7.9 nm and a lattice constant of 0.42 nm. Moreover, the films showed a smooth surface with root mean square (rms) roughness of 2.87 nm. The p-type electric behavior of the films was identified by current modulated ac-Hall effect measurements. The films were exposed to 100 ppm H2 in synthetic air, at room temperature, showing a typical p-type behavior and a sensitivity of 68%, while the response and recovery times were found to be 388 s and 451 s, respectively. Subsequently, the films were also exposed on CH4 showing a sensitivity of 58%, with response and recovery times equal to 1373 s and 95 s, respectively.

    更新日期:2020-01-21
  • Cobalt sulfide nanoparticles: Synthesis, water splitting and supercapacitance studies
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-12
    Rehana Akram; Malik Dilshad Khan; Camila Zequine; Chen Zhao; Ram K. Gupta; Masood Akhtar; Javeed Akhtar; Mohammad Azad Malik; Neerish Revaprasadu; Moazzam H. Bhatti

    Different alkyl xanthate complexes of cobalt (alkyl = Ethyl, Hexyl, Octyl) were synthesized and used for the synthesis of nanoparticles by a solvent-less route. The p-XRD of the nanoparticles showed the formation of the CoS phase only from all precursors. The effect of size and surface capping on energy generation and energy storage applications was investigated. The electrocatalytic performance of the synthesized samples for hydrogen (HER) and oxygen evolution reaction (OER), indicates that CoS synthesized from the octyl xanthate complex (CoS-Oct) showed higher electrocatalytic performance. A lower over potential of 325 mV and 200 mV was observed for CoS-Oct, at a current density of 10 mA/cm2, for OER and HER, respectively. The charge storage performance was also investigated, where an inverse trend was observed i.e. the highest specific capacitance (1500 F/g, at scan rate 2 mV/s) was observed for the CoS sample synthesized from ethyl xanthate (CoS-ET). Similarly, the discharge time for CoS-ET was longer as compared to the other samples, suggesting better performance for the charge storage applications. The use of cobalt xanthate complexes for the preparation of CoS by melt method, and the effect of self-capped and uncapped surface of CoS on supercapacitance and OER/HER performance, has never been investigated before.

    更新日期:2020-01-21
  • Study of morphological and electrical properties of the ZnO/p-Si hetero-junction: Application to sensing efficiency of low concentration of ethanol vapor at room temperature
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-13
    S. Tata; L. Chabane; N. Zebbar; M. Trari; M. Kechouane; A. Rahal

    In this work, thin films of ZnO were deposited by DC reactive sputtering of zinc target under (Ar and O2) gas atmosphere, at a deposition temperature of 100 °C. A series of samples were prepared on both corning glass and p-doped crystalline silicon substrates, at different Ar flow rates (FAr) ranging from 0.5 and 2.5 sccm. The films properties were investigated by atomic force microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results showed thin films with rough surfaces and polycrystalline structure. The electrical study (current-voltage characteristics) of ZnO/p-Si hetero-junctions revealed a rectification behavior. The highest forward current was obtained for FAr = 1.5sccm. The exposure at room temperature of ZnO/p-Si hetero-structures to ethanol vapors showed a high gas sensing response for ZnO/p-Si hetero-junctions with rough surface and high forward current, corresponding to FAr = 1.5 sccm. For a low concentration of ethanol vapor (10 ppm), the dynamic response at room temperature of ZnO/p-Si hetero-junctions revealed a sensitivity ranging from 40 to 80% with response and recovery times of 5 and 3 s respectively. Comparing these characteristics to those already obtained by other teams showed that the elaborated devices in this work are good candidates for fast sensors of low concentrations of ethanol vapors at room temperature.

    更新日期:2020-01-21
  • Enhanced thermoelectric properties of pristine CrSi2 synthesized using a facile single-step spark plasma assisted reaction sintering
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-13
    Naval Kishor Upadhyay; L.A. Kumaraswamidhas; Bhasker Gahtori; S.R. Dhakate; Ajay Dhar

    The current study reports a single-step synthesis of thermoelectric material p-type chromium di-silicide (CrSi2), using reaction sintering of their elemental powders employing spark plasma assisted sintering at optimized processing parameters. This process of single-step synthesis takes only a few minutes in contrast to the conventional processes reported earlier, which take several hours and involve multi-step processing, including arc-melting and/or mechanical alloying followed by spark plasma sintering/hot pressing. Despite employing a facile single-step synthesis process, an enhanced state-of-the-art thermoelectric figure of merit (ZT) ~ 0.19 at 673 K was achieved in pristine single phase CrSi2, which is the highest reported thus far in pristine CrSi2 at this temperature. It was observed that in order to compensate for the loss of Si during high temperature processing, 2.5 at.% of excess Si was found to be optimum in order to obtain a single-phase CrSi2. The synthesized CrSi2 samples were characterized using X-ray diffraction, Field emission scanning electron microscopy and Energy dispersive X-ray spectroscopy, based on which their enhancement of thermoelectric properties has been discussed.

    更新日期:2020-01-21
  • Effects of the inductively coupled Ar plasma etching on the performance of (111) face CdZnTe detector
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-13
    Bing Song; Jijun Zhang; Xiaoyan Liang; Shuhao Zhao; Jiahua Min; Haozhi Shi; Jianming Lai; Linjun Wang

    The effect of inductively coupled Ar plasma etching (ICP-Ar) instead of traditional Br–MeOH etching on the performance of CdZnTe detectors was studied. The optimal ICP etching parameters were determined by experiments. The XPS results indicated that the surface composition of CdZnTe etched by ICP-Ar had no obvious TeOx peak and was closer to stoichiometric ratio than that etched by Br–MeOH. The leakage current of ICP-Ar etched CdZnTe surface was significantly reduced, and the detection performance with the energy resolution was improved by 12%, as compared to Br–MeOH etched sample. Moreover, ICP-Ar etching abandoned the drawbacks of Br–MeOH by producing corrosive gases, making it safer and more environmentally friendly. Therefore, inductively coupled Ar plasma etching is expected to replace Br–MeOH etching and become an effective method for CdZnTe surface treatment.

    更新日期:2020-01-21
  • Doped CuCrO2: A possible material for supercapacitor applications
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-17
    Ramesh Manickam; J. Yesuraj; Krishnendu Biswas

    Delafossites, owing to their layered structural characteristics are mostly known for thermoelectric and Lithium ion battery applications. In the present paper we explore the possibility of using such a delafossite oxide viz. CuCrO2 for use as a supercapacitor material. In this regard, multivalent doping at the Cr site of CuCrO2 delafossite compound was carried out to study the effect on its electrochemical properties. The phase formation and morphological studies carried out by X-ray diffraction and Scanning Electron Microscope (SEM) techniques respectively reveal the presence of a single phase of CuCr1-x(MgTi)x/2O2 (x = 0, 0.05, 0.1, 0.15) with appropriate composition. The electrochemical properties of all the compositions were examined by cyclic voltammetry (CV) using a three-electrode system. The CV studies show an increase in specific capacitance with increasing dopant concentration. The increased electrical conductivity with dopant concentration is the reason for enhanced specific capacitance which is supported by the electrochemical impedance spectroscopic studies. The highest doped composition x = 0.15, gave a specific capacitance value of 248 Fg-1 with the scan rate of 50 mVs−1 and showed good cycle stability up to 2000 cycles.

    更新日期:2020-01-21
  • Fabrication of Cu2O/Bi25FeO40 nanocomposite and its enhanced photocatalytic mechanism and degradation pathways of sulfamethoxazole
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-14
    Yan Huang; Li-chao Nengzi; Xiaoling Li; Lezu Meng; Qingqing Song; Xiuwen Cheng

    In the study, cuprous oxide (Cu2O) combined with sillenite bismuth ferrite (Bi25FeO40) was successfully fabricated through hydrothermal strategy. Subsequently, physicochemical properties of Cu2O/Bi25FeO40 were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption, X-ray photoelectron spectroscopy measurements (XPS), UV visible diffuse reflectance spectroscopy (DRS). The experimental results indicated that Cu2O/Bi25FeO40 exhibited a significantly enhanced photocatalytic activity, which 85.0% of sulfamethoxazole was decomposed in 120 min under irradiation. Afterwards, scavenger experiments have been carried out to determine the contributions of different species and h+ and H2O2 were manifested to be staple reactive species during the process of sulfamethoxazole (SMX) degradation. In addition, Cu2O/Bi25FeO40 nanocomposite showed good stabilities. And the degradation efficiency of SMX still reached 84.9% after five recycle experiments. Furthermore, some plausible degradation pathways of sulfamethoxazole were detected by a high-performance liquid chromatography-tandem mass spectrometry. Finally, the enhanced visible light photocatalytic mechanism was proposed reasonably. Eventually, this study provides a novel strategy to prepare catalyst which could be potentially applied in emerging pollutants elimination.

    更新日期:2020-01-21
  • Green preparation of Carbon Quantum dots using Gingko biloba to sensitize TiO2 for the photohydrogen production
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-14
    Munevver Tuna Genc; Gizem Yanalak; Gulsin Arslan; Imren Hatay Patir

    Carbon Quantum dots (CQDs) were obtained from Gingko biloba by using microwave technique, which is easy, time-saving, cost-effective, non-toxic and environmental friendly way. TiO2 were sensitized by green-prepared CQDs to obtain CQDs/TiO2 composite. The characterizations of the CQDs and CQDs/TiO2 were performed by Transmission Electron Microscopy (TEM), high-resolution TEM (HR-TEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopic (XPS), Photoluminescence (PL) and Fourier Transformed Infrared (FT-IR) spectroscopy. The photocatalytic hydrogen evolution activity of CQDs/TiO2 system was studied under visible light (λ > 420 nm) irradiation in the aqueous solution by using triethanolamine (TEOA) as a sacrificial electron donor. When Pt was used as a co-catalyst, CQDs/TiO2/Pt exhibited improved hydrogen evolution rate (1502 μmol h−1g−1) compared to CQDs/TiO2 composite (665 μmol h−1g−1).

    更新日期:2020-01-21
  • Synthesis of TiO2 nanoparticles coated on cellulose nanofibers with different morphologies: Effect of the template and sol-gel parameters
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-14
    Saba Habibi; Masoud Jamshidi

    TiO2 nanoparticles were coated on cellulose nanofibers (CNFs) as template, in three different forms in sol-gel process. CNFs hydrogel template resulted in porous and highly entangled TiO2 nanofibers. A sheet-like TiO2 structure was obtained, when the CNFs aerogel with almost the same structure was used. Finally, the cellulose hydrogel was transformed to alcogel after exchanging the water by isopropanol to minimize the water content in the sol-gel reaction mixture, and it was used as template in a Stöber-modified sol-gel process to produce TiO2 nanowhiskers and nanosheets. The FESEM images showed that increasing the TTIP amount resulted in a three-dimensional nanowhiskers structure and increment of sol-gel reaction time caused the adhesion of nanowhiskers to each other. After sonication during the sol-gel reaction nanorods were obtained. According to XRD patterns and Raman spectroscopy both the bare TiO2 nanoparticles (TNPs) and alcogel-TiO2 consisted of pure anatase phase. UV–Vis DRS results of TNPs and alcogel-TiO2 nanowhiskers showed that the band-gap value decreased significantly from 2.95 eV to 2.72 eV. The FESEM and TEM images confirmed that by increasing the ammonia content from 0.2 to 0.25 vol% to 0.3–0.6 vol%, the shape of the nanowhiskers changed to nanosheets, and the BET specific surface area increased from 52.308 m2/g for TNPs to 86.367 m2/g for nanowhiskers and 76.115 m2/g for nanosheets. The photocatalytic activity of the samples was evaluated by degradation of aqueous methylene blue solution. In UV light all samples showed photodegradation efficiency of more than 98% in less than 120 min. Under visible light the photodegradation efficiency of TiO2 nanowhiskers in 240 min was 45.24% and 47.26% which were higher than that of TNPs (15.07%) and nanosheets (28%–33%).

    更新日期:2020-01-21
  • Impact of Si(100) doping methods on TiSi2 formation in vertical and horizontal FET structure areas with increasing aspect ratio
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-20
    Diana Hößler

    Due to the increasing complexity of FET structures and the preferred high trench aspect ratios, demanding process challenges exist, not only in the structuring of the contact trenches, but also in the uniform doping of the diffusion area. Previous investigations have mainly analyzed the doping of horizontal contact areas. For this reason, this paper demonstrates how vertical and horizontal contact areas can be doped through the side wall at the same time. For this purpose, relationships between structural geometry and doping methods are studied in order to structure a multitude of contact trenches next to each other in a functional way, which can realize source and drain trenches. By means of an ion implanted test structure, high doping concentrations of up to 1019 cm−3 could be achieved at a depth of approx. 250 nm below the 2.5 μm deep contact trench bottom. The concentration which can be obtained by PSG diffusion decreases rapidly with increasing Si depth. For the first time, it is shown that the dopant particle concentration of ion implantation increases with trench height and proximity to the trench side wall. Accordingly, the electrical conductivity is also higher and the SR value lower. A positive effect of the near-surface doping concentrations on the subsequent C49-TiSi2 formation could be demonstrated, which enables uniform film growth. In contrast, dopant deposition generates asymmetric dopant concentrations and prevents uniform silicide formation as the aspect ratio increases, thus causing higher diffusion area resistances.

    更新日期:2020-01-21
  • Nanoindentation of GaAs/AlAs distributed bragg reflector grown on GaAs substrate
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-20
    Jan Muszalski; Iwona Sankowska; Stanisław Kucharski

    Nanoindentation was used to investigate the mechanical parameters of GaAs/AlAs Distributed Bragg Reflectors. Such heterostructures are commonly employed in surface-emitting optoelectronic devices as LED or lasers. The investigation was carried for fully pseudomorphic AlAs/GaAs heterostructures and compared with bulk GaAs. The nanoindentation tests with sharp (Vickers) and spherical tip were conducted, and pop-in events were observed. We show that below pop-in load, the response of both materials is similar i.e., elastic parameters of the heterostructure and GaAs are practically the same. However, the pop-in events take place at higher loads for heterostructures than for GaAs. This in turn indicates that the heterostructure has a higher resistance to damage. For both materials, the pop-in load depends on loading rate. The possible mechanisms of pop-in are discussed. In the elastic-plastic stage (after pop-in), the heterostructure exhibits lower stiffness and lower hardness than GaAs does. The surface cracks that are generated in the heterostructure during the indentation test continue to grow even when the load is removed.

    更新日期:2020-01-21
  • Current density transient response to variations in synthesis parameters during anodic growth of TiO2 nanotubes
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-18
    Nyasha J. Suliali; Crispin M. Mbulanga; William E. Goosen; Johannes R. Botha
    更新日期:2020-01-21
  • Leakage current lowering and film densification of ZrO2 high-k gate dielectrics by layer-by-layer, in-situ atomic layer hydrogen bombardment
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-18
    Kuei-Wen Huang; Teng-Jan Chang; Chun-Yuan Wang; Sheng-Han Yi; Chin-I. Wang; Yu-Sen Jiang; Yu-Tung Yin; Hsin-Chih Lin; Miin-Jang Chen
    更新日期:2020-01-21
  • Plasmonic gold nanorods mediated p-BFCrO/n-rGO heterojunction in realizing efficient ferroelectric photovoltaic devices
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-21
    H. Renuka; P. Joshna; Waseem Ahmad Wani; B. Harihara Venkataraman; Kannan Ramaswamy; Souvik Kundu

    In this work, we introduce a chemically synthesised lead-free ferroelectric thin film 2% Cr doped BiFeO3 (BFCrO) for possible photovoltaic (PV) applications. The first set of PV devices were fabricated onto ITO/glass electrode by utilizing BFCrO as an active material and Pt as top electrode. The obtained ferroelectric and electrical results were systematically compared with the conventional BFO and the BFCrO device was found to be a potential one. To further enhance the PV performance, highly conducting n-type reduced graphene oxide (rGO) was heterogeneously employed as an electron transport layer (ETL) in between ITO and BFCrO. Surprisingly, the JSC was significantly improved by 1000 times along with amended VOC and FF as compared to the standalone BFCrO device. Furthermore, an attempt has been made to embed plasmonic Au nanorods (NRs) in between rGO and BFCrO, which alleviates the absorbance in heterojunction through localized surface plasmonic effect, ultimately offered remarkable PV performances than conventional BFO one. The Au NRs based BFCrO/rGO PV device exhibited an increased VOC and JSC of 0.63 V and 2.56 mA/cm2, respectively as compared to the BFCrO/rGO device with VOC (0.56 V) and JSC (1.54 mA/cm2). Effort was devoted to establish ferroelectricity in BFCrO and the effect of positive and negative polarizations on J-V measurements were observed in with or without Au NRs based devices. The modulation in charge transport with polarization field and improved photoresponse were explained by projecting a band diagram, which also provides a comprehensive understanding on the operation principle of the fabricated devices.

    更新日期:2020-01-21
  • Optimization of hybrid P3HT:CdSe photovoltaic devices through surface ligand modification
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-20
    M. Elain Hajlaoui; N. Hnainia; Z. Gouid; A. Benchaabane; M.A. Sanhoury; R. Chtourou

    Within the last few years, renewable energy devices have been gaining growing interest and the quest for environmentally friendly efficient photovoltaic cells continues. Amongst commonly used designs, bulk heterojunctions consist of blending a conjugated polymer donor with semiconducting nanocrystals (NCs) as acceptors. These nanocrystals are promising substitutes for fullerene normally used as acceptor, offering better electron mobility, tunable band gap and higher dielectric constant to prevent recombination of charge carrier into excitons. In this work, cadmium selenide nanocrystals (CdSe) capped with different phosphine oxides (R3PO: R = Me2N, Et2N, pyrrolidinyl (Pyrr), piperidinyl (Pip) or octyl groups) were synthesized and characterized using powder XRD and Transmission Electron Microscopy (TEM) Then, we investigated the surface structure of blended poly-3-hexylthiophene (P3HT) and CdSe active layer using Atomic Force Microscopy (AFM). Subsequently, absorption spectroscopy (UV–Vis) and photoluminescence (PL) were used for further optical property characterization. Significant quenching of PL spectra along with a larger absorption band were observed. Importantly, the capping ligand effect on the morphology and the fluorescence quenching was investigated in order to high light the role of ligand modification on the photovoltaic device performance. We reported a performance dependence of hybrid devices on the bulkiness of capping molecules. Moreover, the conversion efficiencies of the elaborated cells show an increase from 0.046% for pure P3HT to 0.46% for the hybrid composite containing Pyrr3PO-capped NCs.

    更新日期:2020-01-21
  • Hydrothermal/electrospinning synthesis of CuO plate-like particles/TiO2 fibers heterostructures for high-efficiency photocatalytic degradation of organic dyes and phenolic pollutants
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-09
    Büşra Çinar; Iklim Keri̇moğlu; Beyza Tönbül; Atakan Demi̇rbüken; Sami Dursun; Ismail Cihan Kaya; Volkan Kalem; Hasan Akyildiz

    CuO–TiO2 p-n heterostructures with tailored compositions were fabricated using hydrothermally derived plate-like CuO particles and electrospun TiO2 fibers and further applied for photocatalytic degradation of typical water pollutants such as methylene blue and 4-Nitrophenol. Effect of varying amount of CuO decoration on TiO2 fibers on microstructure, on phase constitution, and on the optical and photocatalytic properties was investigated. Photocatalytic testing results indicated that the degradation behavior was affected by the amount of CuO particles in the samples. Among all compositions studied, the samples with 1.25 and 0.5 wt% CuO exhibited the highest photocatalytic efficiency under UV (3.3 times higher compared to pure TiO2) and visible light irradiations (3.75 times higher compared to pure TiO2), respectively. The improved photocatalytic performance compared to pure fibers was attributed to particle-fiber architecture, increased and extended light harvesting ability, more efficient charge separation due to staggered band structure and p-n junctions of the heterostructured samples.

    更新日期:2020-01-09
  • Effect of perovskite precursor ratios and solvents volume on the efficiency of MAPbI3-xClx mixed halide perovskite solar cells
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-09
    Hanadi Mehdi; Asya Mhamdi; Abdelaziz Bouazizi

    The triiodide lead methylammonium MAPbI3 perovskite solar cells have attracted big attention especially when they were manufactured with different precursors mainly that based on lead chloride. In this report, the effects of the incorporation of PbCl2 into precursor solutions of the perovskite MAPbI3 on the microstructures, optical and photovoltaic properties were examined. The perovskite solar cells elaborated with the MAPbI3-xClx perovskite films treated by the optimal concentration of (MAI: PbCl2) has showed a preferred crystalline orientation and an improvement of the performances. Furthermore, the effect of different solvent volumes of (DMF: DMSO) on photovoltaic performance was investigated. The highest performance was obtained for the cell made from precursor solution dissolved in DMF resulting from the good interaction of the materials with the perovskite material.

    更新日期:2020-01-09
  • Enhanced performance of perovskite photodetectors fabricated by two-step spin coating approach
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-09
    Swati Chaudhary; Saral Kumar Gupta; Chandra Mohan Singh Negi

    Metal halide perovskite films were prepared using two different deposition techniques, namely one-step spin coating (OSSC) and two-step spin coating (TSSC) and used as the active layer in perovskite photodetectors (PDs). Surface morphology studies revealed that perovskite thin films grown by OSSC exhibited large density of pin holes and non-uniform surface coverage. While, the film produced by TSSC shows full surface coverage with lesser pin holes. By comparing the device performance of the photodetectors based on OSSC and TSSC deposited films, we found that TSSC deposited film based PD demonstrated a significant enhancement in the performance (Responsivity of 1.05 A/W and detectivity of 1.27 × 1011 Jones @ −1 V) in comparison to the PD based on OSSC deposited films (Responsivity of 0.019 A/W and a detectivity of 1.77 × 109 Jones @ −1 V), which can be attributed to the higher absorbance, lesser trap density, narrower trap width, larger carrier mobility and lower leakage current, arising from better surface morphology and crystallinity of TSSC deposited films. Impedance analysis of PD prepared from TSSC film showed a relatively large charge recombination resistance and a long lifetime than PD fabricated from OSSC film, signifying less charge recombination events, which is in consistent with the high performance achieved with the TSSC film based PD.

    更新日期:2020-01-09
  • Fabrication and optimization of hole transport layer NiO for all inorganic perovskite light emitting diodes
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-09
    Shiwei Zhuang; Jing He; Xue Ma; Yang Zhao; Hui Wang; Baolin Zhang

    Perovskite light emitting diodes (PeLEDs) have attracted massive research interest in recent years. In order to obtain better luminescent properties, most attention is paid to the emitting layer perovskite materials. Actually, the other layers such as the transport layers should also be optimized. We proposed the optimization of hole transport layer NiO materials by magnetron sputtering. Effects of RF power, sputtering pressure and sputtering argon-oxygen ratio on surface morphology and electrical properties of NiO film were studied. Sputtering power, pressure and Ar/O2 were set at 90 W, 25 mTorr and 10/40 over the past parameters to optimize the NiO film in our previous ZnO/CsPbBr3/NiO structured all inorganic perovskite LED. SEM, PL, XRD measurements were conducted to characterize the CsPbBr3 having good morphologies, light emitting characteristics, and crystal quality. PeLEDs with and without the optimized hole transport layer NiO were compared. The EL results show that the optimized PeLED has much better electroluminescence characteristics than the one without optimization. Our work demonstrated a possible way to improve the luminescence properties of the PeLED.

    更新日期:2020-01-09
  • Simultaneously improving thermopower and electrical conductivity via polar organic solvents aided layer-by-layer technique
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-08
    Xiaomeng Sun; Tingting Sun; Xiaofang Lu; Lianjun Wang; Wan Jiang

    In recent years, organic/inorganic hybrids capture wide attention due to their advantages in endowing composites with both high Seebeck coefficient and low thermal conductivity originating from inorganics and polymer, respectively. However, simply blending tend to weaken this advantage, resulting in lower thermoelectric performance than that of single organics or inorganics. Here we propose a polar organic solvents aided layer-by-layer (OS-LbL) technique to prepare high performance nanocomposite films comprising poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and Sb2Te3 nanocomposites. Polar organic solvents not only promote the dispersion of Sb2Te3 nanoplates but also post-treat the PEDOT:PSS layer at the hetero-junction interface, successfully increasing the electrical conductivity and thermopower at the same time. Besides, the organic/inorganic interface inducing by OS-LbL promotes a low thermal conductivity of 0.0522 Wm−1K−1. As a result, a maximum ZT value up to 0.10 at room temperature. The results show that using OS-LbL method to combine PEDOT:PSS with Sb2Te3 nanoplates is a promising pathway to achieve polymer-based, high-performance thermoelectric applications.

    更新日期:2020-01-08
  • 更新日期:2020-01-08
  • Small molecular material as an interfacial layer in hybrid inverted structure perovskite solar cells
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-08
    Faiazul Haque; Haimang Yi; Jihoo Lim; Leiping Duan; Hong Duc Pham; Prashant Sonar; Ashraf Uddin

    Hybrid halide perovskites are becoming increasingly popular due to their immense potential to be used as a low cost and easily processable solar cell technology. Interfacial engineering is believed to be one of the crucial ways to improve the device performance. In this work, we report the introduction of a small molecular interfacial layer 4,4’-(naphthalene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TPA-NAP-TPA) between the traditional hole transporting layer poly (3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) and perovskite (Cs0.15FA0.85PbI3) active layer. Systematic investigations indicate that the incorporation of the small molecular interfacial layer improves the inverted device efficiency by 7% relative. The crystallinity and morphology of the perovskite formed on top of the PEDOT:PSS/TPA-NAP-TPA is favourable compared to the perovskite formed on top of pristine PEDOT:PSS layer. The improvement in the PCE is attributed to increased photocurrent generation. The devices containing the interfacial layer has also depicted improved quantum yield which is in line with the maximised average JSC. Furthermore, the devices with PEDOT:PSS/TPA-NAP-TPA interfacial layer retained 60% of their initial efficiency after 30 days, which is 30% higher than the devices with pristine PEDOT:PSS layer. Including interfacial layers such as TPA-NAP-TPA could be a viable technique in order to enhance the performance and stability of inverted structure perovskite solar cells.

    更新日期:2020-01-08
  • Study of acidosis, neutral and alkalosis media effects on the behaviour of activated carbon threads decorated by zinc oxide using extended gate FET for glucose sensor application
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-08
    Ali M. Khalifa; S.A. Abdulateef; E.A. Kabaa; Naser M. Ahmed; Fayroz A. Sabah

    In recent times, semiconductor-carbon composite microstructure offers new prospects in bio-chemical sensor research. In this study, hexagonally structured zinc oxide micro rods (ZnOMRs) were synthesized on activated carbon threads (ACTs) using the chemical bath in the absence of a ZnO seed layer. The ZnOMRs/ACTs based extended gate field effect transistor (EGFET) was characterized as a bio-chemical sensor for pH and glucose in acidosis, neutral and alkalosis media. The ZnOMRs/ACTs based EGFET sensor exhibited glucose sensitivities in terms of reference voltage (VRef) of (20.71, 18.21, and 16.72) mV/mM and drain source current (IDS) of (29.00, 25.60, and 23.62) μA/mM for pH values of 7.2, 7.4, and 7.6, respectively, at room temperature. Thus, the glucose sensitivity of the ZnOMRs/ACTs based EGFET increased with decrease in pH, due to the increased participation of hydrogen ions in the electrochemical exchange reaction between the solution and ZnOMRs/ACTs electrode. Based on the high sensitivity, ZnOMRs/ACTs composite could be a favourable micromaterial for bio-chemical sensor applications.

    更新日期:2020-01-08
  • Effect of the hydrostatic pressure and shell’s Al composition in the intraband absorption coefficient for core/shell spherical GaAs/AlxGa1−xAs quantum dots
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2020-01-08
    K.A. Rodríguez-Magdaleno; M.E. Mora-Ramos; R. Pérez-Álvarez; J.C. Martínez-Orozco

    In this paper we theoretically investigate the role of hydrostatic pressure by analyzing its influence on potential barrier’s height in GaAs/AlxGa1−xAs core/shell spherical quantum dots. The values of hydrostatic pressure considered here are always below the Γ−X crossover. In addition, we take into account the barrier shell’s size effects and the barrier’s aluminum concentration, looking for a description of the features of the intraband optical absorption coefficient in the system. The electronic structure is calculated within the effective mass approximation. From the numerical point of view the hybrid matrix method was implemented to avoid numerical instability issues that appears in the conventional transfer matrix method. The main intersubband optical transition is considered to take place between the 1s and 1p computed electronic states. The results show that the absorption coefficient undergoes first a red-shift and later a more pronounced blue-shift, depending on the AlxGa1−xAs barrier width (wb1). The absorption coefficient experiences a blue-shift as the barrier’s aluminum concentration increases, and it is non monotonically red-shifted as the hydrostatic pressure augments, due to the barrier’s height pressure dependency. For the chosen system parameters, the absorption coefficient resonant peak lies within the range of 20 to 30 meV, that corresponds to the THz frequency region. Accordingly, this system can be proposed as a building block for photodetectors in the THz electromagnetic spectrum region.

    更新日期:2020-01-08
  • Impact of alloying elements (Co, Pt) on nickel stanogermanide formation
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-31
    Andrea Quintero; Patrice Gergaud; Jean-Michel Hartmann; Vincent Reboud; Eric Cassan; Philippe Rodriguez

    The impact of Pt or Co as alloying elements for Ni-based metallization of GeSn layers has been investigated. As far as the solid-state reaction is concerned, the overall phase sequence is the same for all metallizations: at low temperature, a Ni-rich phase is obtained; it is then consumed to form the low resistivity mono-stanogermanide phase. Nevertheless, the addition of an alloying element has an impact on Ni consumption, Ni-rich and mono-stanogermanide phases’ formation temperatures. Moreover, the addition of Co or Pt positively impacts Sn segregation by delaying this phenomenon. Co has a weak influence on morphological and electrical properties. On the other hand, Pt improves the surface morphology by delaying the Ni(GeSn) phase agglomeration and enhancing the process window in which the sheet resistance remains low.

    更新日期:2019-12-31
  • Effect of doping Mg on the structure and optical properties of LiNbO3 films prepared by radio-frequency magnetron sputtering
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-31
    Li Zhao; Laixiang Shi; Ji Wang; Jun Yan; Yunlin Chen; Yanqing Zheng

    High-quality magnesia-doped lithium niobate (LN: MgO) films were deposited by radio-frequency magnetron sputtering. The deposited films were characterized for their structural, surface morphology and elemental atomic percentages by X-ray diffraction, Raman spectra, scanning electron microscopy and energy dispersive spectroscopy, respectively. The results show that the LN: MgO films without impurities phase has a preferred orientation of (012) plan. The optical properties of LN: MgO films were studied systematically. It reveals that the average transmittance of LN: MgO film is related to the atomic percentage of Mg element and the maximum of that is 89% when the atomic percentage of Mg element is 0.8%. The optical band gap can be adjusted from 3.85 eV to 4.04 eV by changing deposition conditions to control the grain size of the films. Moreover, the optical damage threshold of LN: MgO films was investigated and the value of that was as high as 4.68 × 104 W/cm2. These characteristics of LN: MgO films may provide promising applications in the fabrication of novel optoelectronic devices.

    更新日期:2019-12-31
  • Improved resistive switching behavior of multiwalled carbon nanotube/TiO2 nanorods composite film by increased oxygen vacancy reservoir
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-31
    Navaj Mullani; Ijaz Ali; Tukaram D. Dongale; Gun Hwan Kim; Byung Joon Choi; Muhammad Abdul Basit; Tae Joo Park

    The non-linear nature in the current-voltage relationship and good resistive switching characteristics were demonstrated with the help of TiO2 nanorods-functionalized multiwalled carbon nanotube (fMWCNT) composite grown by the low-cost hydrothermal method. The composites were characterized by X-ray diffraction, scanning electron microscopy, Raman, photoluminescence, and X-ray photoelectron spectroscopy to investigate the structural, morphological, and chemical composition of composite films. The resistive switching characteristics of the TiO2-fMWCNT nanocomposites were found to be strongly dependent on the fMWCNT concentration. The enhanced switching performance is associated with the surface nanostructure and chemical composition of the nanocomposites. Owing to the hierarchical rutile TiO2 nanorods and opportune fMWCNT content, the nanocomposite based device with 0.03 wt % fMWCNT exhibited the best resistive switching performance with good endurance and retention non-volatile memory properties. Interestingly, with the optimized stoichiometric composition and operation conditions, forming-free, low operational voltage, self-rectifying like properties have been simultaneously achieved, which are some of the prerequisites for next-generation memory devices. In addition to this, the double-valued charge-magnetic flux nature of the developed devices was demonstrated. The experimental current-voltage characteristics are well-matched with the Ohmic and Schottky conduction mechanisms.

    更新日期:2019-12-31
  • 更新日期:2019-12-31
  • Photoelectrochemical reduction of CO2 with TiNT
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-31
    M.A.L.R.M. Cortes; S. McMichael; J.W.J. Hamilton; P.K. Sharma; A. Brown; J.A. Byrne

    In order to reduce CO2 emissions and utilise CO2 as a useful by-product, artificial photosynthesis is being explored for carbon capture and utilisation. Semiconductor photocatalysts excited by solar energy may be used to convert CO2 to fuels or useful chemicals, e.g. CO, CH4, CH3OH. The photocatalytic reduction of CO2 to useful products has been widely studied in order to overcome the greenhouse effect and the current energy necessities. However, this reaction has proved to be extremely low efficiency when compared to other processes. In order to improve these yields, photoelectrochemical reduction of CO2 has been considered, since it combines photocatalysis and electrocatalysis. To this end, a two compartment photoelectrochemical cell (PEC) has been designed and fabricated for the reduction of CO2. This custom built reactor consists of dual phases, where gas phase CO2 is feed into the cathode compartment and an aqueous phase in the anode compartment. The anode and cathodes for a sandwich were the anode perforated foil on exposing aligned titania nanotubes to electrolyte bonded to nafion; which forms a bridge to Pt deposited carbon cloth cathode electrode in gas phase compartment. CO2 reduction products were detected with GC connected to the reactor. The PEC reactor improved the yield and the formal quantum efficiency compared to our previous studies using photocatalytic reactors.

    更新日期:2019-12-31
  • Fabrication of SrTiO3/g-C3N4 heterostructures for visible light-induced photocatalysis
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-26
    Meiriele Antunes Ferreira; Gelson T.S.T. da Silva; Osmando F. Lopes; Valmor R. Mastelaro; Caue Ribeiro; Manoel J.M. Pires; Andréa R. Malagutti; Waldir Avansi; Henrique A.J.L. Mourão

    We investigated a new method for the preparation of visible light-activated heterostructured photocatalysts made up of SrTiO3 (STO) and g-C3N4 (CN). The photocatalysts were synthesized by the polymeric precursor method to obtain STO, which was further thermally treated at 550 °C for 2 h in presence of melamine at different proportions for CN formation. The SrTiO3/g-C3N4 heterostructures were termed as STOCN-Mel88%, STOCN-Mel92%, STOCN-Mel95%, STOCN-Mel97% and STOCN-Mel99% indicating the use of melamine at 88%, 92%, 95%, 97% or 99%. The SrTiO3/g-C3N4 heterostructures were characterized for their crystalline structure, optical properties, thermal stability, morphology and surface composition, and photocatalytic potential, which was evaluated by photodegradation of methylene blue dye and amiloride under visible light. The melamine content exhibited a strong influence on the formation of CN, as well as on the bulk structure, surface and photocatalytic properties of the SrTiO3/g-C3N4 heterostructures. The heterostructures were catalytically active under visible light due to their reduced band gap energy. The presence of oxygen vacancies in the STO phase associated with the CN phase improved the photogenerated electron-hole charge separation in the SrTiO3/g-C3N4 catalysts. The synthesis described here is efficient in obtaining visible light-activated photocatalysts that are applicable to photocatalytic processes under solar light.

    更新日期:2019-12-27
  • Layer and size distribution control of CVD-grown 2D MoS2 using ALD-deposited MoO3 structures as the precursor
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-25
    Mustafa Demirtaş; Cem Odacı; Yahaya Shehu; Nihan Kosku Perkgöz; Feridun Ay

    We study the use of atomic layer deposited MoO3 films acting as Mo precursor, in a subsequent step to grow uniform MoS2 structures with excellent layer and size control over the entire substrate by chemical vapor deposition (CVD)/sulfurization process. ALD MoO3 provides two critical advantages in CVD/sulfurization of MoS2, which are the uniform sublimation and control of the amount of the Mo precursor vapor. While uniform sublimation of the MoO3 film provides uniform Mo vapor enabling reproducible growth of MoS2 on the entire substrate, control of the amount of Mo precursor provides the size and layer tuning. This control is achieved by changing the number of cycles in the ALD process. The MoO3 films are deposited on 300 nm SiO2/Si substrates using Mo(CO)6 and remote O2 plasma at 160 °C. As-deposited ALD MoO3 films are annealed at 400 and 600 °C to demonstrate the uniform nucleation domains and sublimation taking place during CVD/sulfurization. Both as-deposited and post-annealed ALD MoO3 films are characterized using spectroscopic ellipsometry, μRaman, and FTIR-ATR and AFM. For MoS2 structures, photoluminescence measurements are additionally performed to verify mono and multi-layered formations. Sparsely dense monolayer MoS2 triangles, with an edge length of ~40 μm and a thickness of ~0.78 nm are obtained with a 150-cycle MoO3 process due to an optimal distance between the nucleation domains. Moreover, as the ALD-cycle number is increased, these nucleation domains become dense, which causes the MoS2 structures to be multi-layered. It is anticipated that our results present a new possibility of controlling the formation of 2D MoS2 structures for various optoelectronic applications.

    更新日期:2019-12-26
  • Structure, substructure and chemical composition of ZnO nanocrystals and films deposited onto flexible substrates
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-12
    О. Dobrozhan; І. Shelest; А. Stepanenko; D. Kurbatov; M. Yermakov; A. Čerškus; S. Plotnikov; А. Opanasyuk

    In this paper, ZnO films were deposited onto flexible polyimide substrate by spraying suspension containing nanocrystals synthesized by polyol method. Afterward, ZnO films were annealed at 200–400 °C for 10–60 min. X-ray diffraction (XRD) technique, scanning, transmission electron and atomic force microscopy, Fourier-transform infrared (FTIR) spectroscopy were used to study the dependencies of phase composition, texture quality, coherent scattering domain (CSD) sizes, microdeformations, microstresses, dislocation densities, lattice parameters, chemical composition on the physico-technical preparation conditions of the obtained ZnO films. The conditions were determined to obtain flexible ZnO films with suitable properties to use in the electronic microdevices.

    更新日期:2019-12-26
  • 更新日期:2019-12-26
  • Preparation of BiOBr-Bi heterojunction composites with enhanced photocatalytic properties on BiOBr surface by in-situ reduction
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-12
    Zhanyao Gao; Binghua Yao; Fan Yang; Tiantian Xu; Yangqing He

    A new kind of BiOBr-Bi composite with improved photocatalytic capabilities was successfully prepared by in-situ reduction. The X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet–visible spectroscopy (UV–VisDRS), X-ray photoelectron spectroscopy (XPS), Brunner-Emmet-Teller measurements (BET), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and the electron paramagnetic resonance (EPR) were used to characterize the morphological structures, physical properties and surface element composition of the photocatalysts. In addition, photocatalytic activity was evaluated by degrading the antibiotic norfloxacin (NOR). The results showed that the BiOBr-Bi (40 mmol/L NaBH4) had the highest activity. The degradation rate reached 97.2%. The half-life of NOR was shortened to 25 min. Moreover, the results of capture experiments indicated that the main active groups involved in the photocatalytic process under visible light conditions were ·O2- and h+. The reason why the activity of the BiOBr-Bi material photocatalyst increased is that the heterojunction formed by BiOBr with wider bandgap and Bi metal with a lower Fermi level effectively inhibits the recombination of holes and photogenerated electrons, which leads to the enhancement of oxidation capacity.

    更新日期:2019-12-26
  • Potassium tartrate as a complexing agent for chemical mechanical polishing of Cu/Co/TaN barrier liner stack in H2O2 based alkaline slurries
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-14
    Lianjun Hu; Guofeng Pan; Can Li; Xinbo Zhang; Jia Liu; Ping He; Chenwei Wang

    The chemical mechanical polishing (CMP) of Cu/Co/TaN barrier liner stack of the sub-14nm devices was associated with several challenges, one of which was to screen out the desired slurries formulation. In this paper, the preliminary screening of cobalt (Co) slurries, combined with the orthogonal test method, was reported systematically for the first time. Based on this, the effects of SiO2, H2O2, potassium tartrate, and TT-LYK on the Co removal rates (RRs) were investigated. The corrosion and polishing behavior of the Co in the slurries containing the above additives were investigated by in-situ OCP measurements, potentiodynamic measurements, and polishing experiments. X-ray photoelectron spectroscopy (XPS) measurements were performed to characterize the complexation mechanism between Co and potassium tartrate. It was found that the slurries containing 5 wt% SiO2, 1 wt% H2O2, and 1.2 wt% PT with 900 ppm TT-LYK at pH 9 was a better candidate for Co barrier planarization and effective in minimizing the galvanic corrosion of Co and Cu under Polishing conditions. Finally, Cu/Co/TaN wafers polished with the candidate slurries showed a good RR selectivity. And the atomic force microscopy (AFM) measurements showed excellent post-polish surfaces.

    更新日期:2019-12-26
  • Microwave-assisted chemical synthesis of Zn2SnO4 nanoparticles
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-18
    Odín Reyes; Mou Pal; J. Escorcia‐García; Rocío Sánchez-Albores; P.J. Sebastian

    In this study it is presented the synthesis of octahedron-like Zn2SnO4 (ZTO) nanoparticles by microwave-assisted chemical synthesis and their characterization. The effect of temperature, time of reaction and reactant concentration on structural, morphological and optical properties of the particles was studied. The samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and diffuse reflectance. The results showed that it is necessary to carry out the synthesis at 200 °C with times more than 50 min to obtain a single phase ZTO. The decrease in reactant concentration promotes the reduction of particle size (ranging from 80 to 120 nm) and increase in the band gap above 4.0 eV.

    更新日期:2019-12-26
  • Radiation stability and reliability of Cu–ZnO/P3OT hybrid heterostructures under swift heavy ion irradiations
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-24
    Jitendra Singh; Himanshi Gupta; A. Kumar; R.G. Singh; Fouran Singh

    Hybrid heterostructures (HH's) were prepared by depositing conducting poly (3-octylthiophene) (P3OT) polymer and Cu-doped zinc oxide (Cu–ZnO) composites films onto indium-doped tin oxide (ITO) substrate using an ultra-sonication cast technique. The weight percentage (wt%) of Cu–ZnO was varied such as 3 wt% and 5 wt% for heterostructure studies. In the HH's, P3OT works as hole-transporting and an electron donor (i.e. hole acceptor) material, while the Cu–ZnO was used as an electron-transporting and hole donor (i.e. electron acceptor) material. The radiation stability and reliability of HH's was studied by performing in-situ current-voltage (I–V) measurements during swift heavy ion (SHI) irradiation by 80 MeV O6+ and 120 MeV Ag9+ ions at increasing ion fluences. Additionally, the in-situ capacitance-voltage (C–V) measurements at frequencies of 1 MHz and 5 MHz were also performed under both the ion irradiations as a function of ion fluences. It was observed that the SHI irradiation-induced secondary charged particles are mainly responsible for modifying the heterostructures properties by depositing energy in the hybrid layer, interfacial region, and ITO substrate. The modification mostly occurs in terms of irradiation-induced various types of defects at the interface of heterostructures. However, after irradiation, minor/insignificant changes in the I–V and C–V characteristics were observed reflecting the radiation stability and reliability of HH's. Therefore, this study may emerge out to be very fascinating for an in-depth understanding of the interaction processes exchanged by primary and secondary charged particles besides the possible applications in radiation harsh environment of such hybrid materials.

    更新日期:2019-12-26
  • Structural, opto-electronic and photoelectrochemical properties of tin doped hematite nanoparticles for water splitting
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-19
    Satirtha K. Sarma; Ratan Mohan; Anupam Shukla

    For application in photoelectrochemical water splitting, pristine and Sn doped (1%, 3% and 5%) hematite nanoparticles were prepared hydrothermally via a two step heating process. XRD results showed that the products match the rhombohedral crystal system. The peak broadening of hematite nanoparticles due to small crystallite size and strain were analyzed by Scherrer's equation and Williamson Hall plot method respectively. A decrease in crystallite size and an increase in lattice strain is observed with dopant addition. Structural change from nanorods to nanocorals is seen for the Sn doped hematite products. Selected Area Diffraction patterns reveal crystallinity of both the doped and undoped powders. Sn 3d XPS peak analysis reveals that Sn has been doped into the hematite lattice. Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy analysis confirm that 1% Sn doped hematite has the highest photocurrent density (3 mA/cm2 at 1 V vs. Ag/AgCl) and least charge transfer resistance among the doped products. UV-VIS, Photoluminescence and Mott-Schottky analysis further show that optimum optical and electrical properties are observed for hematite doped with 1% Sn.

    更新日期:2019-12-26
  • Optical and magnetic properties of Dy3+ doped CdS dilute magnetic semiconductor nanoparticles
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-18
    Shivani Jindal; Puneet Sharma

    Hydrothermally synthesized Cd1-xDyxS (x = 0.0, 0.05 and 0.10) nanoparticles were investigated for its structural, morphological, optical and magnetic properties. The single wurtzite phase was confirmed for all compositions. HR-TEM micrographs revealed spherical morphology of nanoparticles. The average particle size found to decrease from 40 nm to 30 nm with Dy3+ doping. The optical band gap was increased from 2.44 eV (x = 0.0) to 2.55 eV (x = 0.10). The luminescence peak at 568 nm due to Dy3+ transition (4F9/2 → 6H13/2) was observed. Magnetic analysis confirmed room temperature ferromagnetism in all the samples. M-H loop of doped nanoparticle showed enhanced magnetization with paramagnetic contribution.

    更新日期:2019-12-26
  • Photoluminescence study of interfacial charge transfer and photocatalytic activity in titanium dioxide/copper multilayer film
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-23
    Manas Sittishoktram; Phasin Yaemsanguansak; Rungroj Tuayjaroen; Piyapong Asanithi; Tula Jutarosaga

    The 100-nm titanium dioxide (TiO2) thin film and its composites with copper (Cu) underlayers of various thicknesses, 4 nm–16 nm, were fabricated on glass substrates by a DC-magnetron sputtering technique. Optical properties of the pristine and the composite films revealed that increasing Cu underlayer thickness greatly increased their absorption in the entire visible region, leading to a decrease in the band gap energy. This should significantly enhance the solar-driven catalytic activity. However, it was found that the photocatalytic activity under the UV radiation determined from photo-degradation of methyl orange (MO) of thick Cu underlayer films exhibited the reduction in degradation rate. The photoluminescence indicated that Cu nanoparticles at TiO2/Cu interface layer not only generated shallow level defects in TiO2 band gap but also acted as recombination centers for photo-generated carriers. This phenomenon was the result of the presence of Cu surface roughness as well as the presence of large aggregates in thick Cu layers. Therefore, the life time and the number of free carriers transported to the TiO2 surface decreased causing the reduction in photodegradation activity of TiO2 composite films.

    更新日期:2019-12-26
  • 更新日期:2019-12-26
  • The formation of ZnO structures using thermal oxidation: How a previous chemical etching favors either needle-like or cross-linked structures
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-23
    H. Rojas-Chávez; H. Cruz-Martínez; F. Montejo-Alvaro; Rurik Farías; Y.M. Hernández-Rodríguez; A. Guillen-Cervantes; A. Ávila-García; N. Cayetano-Castro; D.I. Medina; O.E. Cigarroa-Mayorga

    Thermal oxidation of Zn polycrystalline elemental foils –previously etched at different chemical conditions– was used to study the formation of ZnO structures. Two distinct etching solutions were used: 0.5 M HNO3 and 11 M HNO3. Based on field emission scanning electron microscopy results, by modifying the etching conditions, the ZnO structures were different regarding morphology: needle-like ZnO microstructure arrays were formed when Zn foil was chemically etched using the 0.5 M HNO3 solution, whilst a cross-linked morphology was obtained when the etching solution changed to 11 M HNO3 concentration. However, the elemental mapping showed identical chemical composition of both kinds of ZnO microstructures. The focused ion beam-transmission electron microscopy specimens revealed the occurrence of ZnO nanostructures, in both kinds of as-oxidized samples, obtained after 2 h of thermal oxidation at 400 °C. Finally, both needle- and cross-linked microstructures were evaluated in terms of their optical properties. According to the experimental findings, it was found that these structures can be applied in optoelectronic devices working around the green range of the visible electromagnetic spectrum, exhibiting the cross-linked sample the highest radiation intensity.

    更新日期:2019-12-26
  • Role of growth temperature in photovoltaic absorber CuSbSe2 deposition through e-beam evaporation
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-23
    Deepak Goyal; C.P. Goyal; H. Ikeda; P. Malar

    In this study, CuSbSe2 chalcostibite thin films were deposited on glass substrates held at different temperatures using e-beam evaporation from the pre-synthesized CuSbSe2 bulk source material. Bulk CuSbSe2 source compound was synthesized by mechanical ball milling of constituent elements. Substrate temperature and growth condition were optimized to obtain the near stoichiometric chalcostibite thin films. Structural, morphological and optical properties of the synthesized thin films were investigated using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), dynamic force microscopy (DFM), UV–vis–NIR spectroscopy and Raman spectroscopy. Positive value of the measured hall coefficient indicated the p-type nature of CuSbSe2 thin films having a carrier concentration of 5.6 × 1015 cm−3. The thin films were found to have a direct optical band gap (Eg) value of ~1.2 eV and absorption coefficient greater than 104 cm−1.

    更新日期:2019-12-26
  • Influence of CeO2 loading on the structural, textural, optical and photocatalytic properties of single-pot sol-gel derived ultrafine CeO2/TiO2 nanocomposites for the efficient degradation of tetracycline under visible light irradiation
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-23
    Manoj Pudukudy; Qingming Jia; Jingyou Yuan; Sivagnanam Megala; Ramesh Rajendran; Shaoyun Shan

    A single-pot surfactant-free sol-gel method is reported for the facile and bulk synthesis of ultrafine-nanospherical CeO2/TiO2 composites with different CeO2 loadings and their photocatalytic-activity for the degradation and mineralization of tetracycline (TC) under visible-light irradiation is investigated for the first time. The incorporation of CeO2 favored the controlled crystalline growth of TiO2 in its anatase phase, and their crystallinity and particle size were significantly decreased. The textural and optical properties of TiO2 were also improved with the incremental addition of CeO2 by increasing their specific surface-area and visible-light absorption respectively. The optical band gap of TiO2 decreased to 2.24 eV with the incorporation of 1% CeO2 and it further decreased to 2.21 eV with the incremental amount of CeO2. Due to the formation of heterojunction in the composite, the recombination rate of electron-hole pairs was significantly decreased. A highest TC removal efficiency of ~99% was observed for 4% CeO2/TiO2 composite for a period of 80 min of visible-light irradiation. Moreover, 88.2% TC mineralization efficiency was achieved for a period of 240 min of visible light irradiation. The enhanced catalytic-activity could be attributed to the synergy of high degree of adsorption followed by an enhanced photocatalysis at the heterointerface formed by the adjacent contact between TiO2 and CeO2. The synergistic effects of low-particle size, high surface-area, enhanced visible-light absorption, reduced band-gap, and increased life-time of the photogenerated charge-carriers through the formation of heterointerface contributed to its high photocatalytic activity. The hydroxyl and superoxide-anion radicals played a superior role in the photocatalytic process. Moreover, the composites retained its efficiency for seven-cycles of reaction without any significant-loss in its activity and structural and textural stability.

    更新日期:2019-12-26
  • Composition, structure and functional properties of nanostructured PbSe films deposited using different antioxidants
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-11-29
    Larisa N. Maskaeva, Victoria M. Yurk, Vyacheslav F. Markov, Mikhail V. Kuznetsov, Vladimir I. Voronin, Ravil D. Muhamediarov, Gregory V. Zyrianov

    By means of chemical bath deposition of selenourea in the presence of ammonium iodide and antioxidants (C6H8O6, Na2SO3, Na2SO3 + C6H8O6, SnCl2) high adhesion nanostructured films of PbSe with a thickness of 300–690 nm were obtained. Depending on the type of antioxidant introduced into the reaction mixture, the dimensions of the crystallites forming the PbSe film in the series listed decrease from 60 ± 10 to 8 ± 2 nm with simultaneous growth from 0.21 ± 0.01 to 1.25 ± 0.15% of microstresses. An increase in the lattice constant of as-deposited lead selenide from 0.6129(8) to 0.6265(9) nm correlates with an increase in the content of iodine in the PbSe film. Using X-ray diffraction, scanning electron microscopy with EDX-analysis and X-ray photoelectron spectroscopy, we investigated the effect of annealing PbSe films on their elemental, phase composition, lattice parameters and surface morphology. It is established that the annealed PbSe films are multiphase and contain PbSeO3, PbSeO4, PbI2. Low-temperature studies in the range of 213–333 K allowed us to determine the PbSe band gap, ranged from 0.265 to 0.349 eV, which depends strongly on a type of antioxidant. PbSe films synthesized using ascorbic acid and tin (II) chloride have anomalously high responsibility at relatively low temperatures, which makes it possible to manufacture highly sensitive IR detectors on their basis.

    更新日期:2019-12-11
  • 更新日期:2019-12-11
  • Incorporation of Co2+ in CdS quantum dots for solar cell applications
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-03
    K. Veerathangam, Muthu Senthil Pandian, P. Ramasamy

    Spin coating and successive ionic layer adsorption and reaction (SILAR) method were adopted to deposit commercial TiO2 (Degussa-P25), un-dopedCdS and Co2+-doped CdS quantum dots (QDs). Characteristic peak for CdS, TiO2and FTO were observed in powder X-ray diffraction pattern of the prepared samples. Co2+-doping was confirmed through energy dispersive X-ray spectroscopy and elemental mapping analysis. Spherical shaped morphology was observed in field emission scanning electron microscopy (FE-SEM). Measured size of CdS is ~8 nm and the TiO2 is ~20 nm through HR-TEM imaging. The maximum absorption range was observed as 570 nm for 3% Co2+-doped CdS QDs. Power conversion efficiency of un-doped CdS and 3% Co2+-doped CdS QDs were 0.54% and 1.21% respectively. It indicated that up to 3% Co2+-doping in CdS QDs leads to remarkable enhancement in the optical absorption, absorption range and photovoltaic performance under chosen experimental conditions.

    更新日期:2019-12-11
  • Very low-temperature growth of silicon thin films using chlorinated precursors and optical properties
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-05
    Javitt Linares, A. López-Suárez, C. Ramos, M. Picquart, M.F. García-Sánchez, A. Dutt, G. Santana

    In this work, the effect of the very low substrate temperature and hydrogen dilution on chemical, structural, and optical properties of polymorphous silicon thin films (pm-Si:H) using dichlorosilane as a silicon gas precursor in the plasma enhanced chemical vapor deposition (PECVD) was analyzed. The films were synthesized at a lower deposition temperature in the range from 60 to 150 °C and two H2 dilutions of 60 and 100 sccm. Hydrogen incorporation in silicon thin films has been studied by Elastic Recoil Detection Analysis (ERDA) and Fourier Transform Infrared Spectroscopy (FTIR). FTIR was also used to verify the chemical stability of the material as a function of oxidation state and hydrogen effusion. The ERDA analysis evidenced that the hydrogen content typically does not exceed 30 at. %, and the lowest value obtained is around 10 at. %. With Raman spectroscopy, the crystalline fraction was obtained in the range of 5–20%, and the average size of the embedded nanocrystals was found to be between 2 and 3 nm, which was cross-checked by High-Resolution Transmission Electron Microscopy (HRTEM). Finally, by UV–Vis spectroscopy, the effective optical band gap of this material has been calculated, and the value was found to be around 1.6 eV (absorber layer) for the samples with 100 sccm of H2 dilution and around 2.2 eV (window layer) for the samples with 60 sccm of H2 dilution. Overall the increase in the substrate temperature resulted a better ordering in the amorphous matrix, whereas, with the increase in the hydrogen dilution an improvement in the structure factor was observed. Suitable properties of the deposited material in the present work could be useful for the development of a thin silicon layer for different silicon solar cell technologies.

    更新日期:2019-12-11
  • All-inorganic, hole-transporting-layer-free, carbon-based CsPbIBr2 planar perovskite solar cells by a two-step temperature-control annealing process
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-06
    Cheng Wang, Junsen Zhang, Jipeng Duan, Li Gong, Jie Wu, Liangxiang Jiang, Conghua Zhou, Haipeng Xie, Yongli Gao, Haiping He, Jianguo Lu, Zhishan Fang, Bojing Lu

    In this paper, all-inorganic CsPbIBr2 thin films were annealed by a two-step temperature-control process. All-inorganic, hole-transporting-layer-free, carbon-based planar perovskite solar cells (PSCs) with these CsPbIBr2 thin films (FTO/c-TiO2/CsPbIBr2/C) were fabricated. The effect of different first-step annealing temperatures during the two-step temperature-control process (50 °C/280 °C, 80 °C/280 °C, 100 °C/280 °C, 150 °C/280 °C, 180 °C/280 °C) on the photovoltaic conversion efficiency (PCE) of PSCs was investigated for the first time. When the first-step annealing temperature was 150 °C and the second-step annealing temperature was 280 °C, the highest efficiency of 8.31% was obtained. Without encapsulation, the solar cell could retain 97% of the initial PCE, when it was stored at 80 °C and zero humidity for 8 days. For comparison, solar cells with CsPbIBr2 films annealed by a one-step temperature-control process were fabricated. The highest PCE was 4.98%. From this, we could see that there is an increase of 66.9% in PCE, through using a two-step temperature-control annealing process. And also, in order to investigate why the PSCs by a two-step temperature-control annealing process has a higher PCE, all kinds of measurements were done for the first time. According to the results of the measurements, the perovskite film annealed by a two-step temperature-control process has a bigger crystal size, fewer grain boundaries, stronger PL and UV–vis absorption intensities, longer lifetime of minority carriers, less energy loss for hole transporting.

    更新日期:2019-12-11
  • Enhancement of the photocatalytic activity of N-doped TiO2 nanograss array films by low-temperature sulfur doping
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-05
    Te Hu, Jiancheng Yan, Yifei Hu, Tongyang Liu, Sujun Guan, Yun Lu, Liang Hao, Touwen Fan, Dongchu Chen

    Moderate in-situ chemical oxidation of Ti meshes was used to prepare nitrogen-doped (N-doped) anatase TiO2 nano-grass array films with urea as the nitrogen source. Further sulfur doping through immersion of the films in a thiourea solution at a relatively low temperature of 353 K was subsequently performed to enhance the visible-light-driven photocatalytic activity of the films. SEM images confirmed that the loose microstructure of the nanograss arrays became compact after N-doping or N, S co-doping. N-doping and N, S co-doping decreased the band gap values of the TiO2 films and increased the effective visible light utilization. XPS analysis revealed that nitrogen mainly existed in interstitial form. Subsequent sulfur ions appeared as S6+, S4+, and S2−, with S6+ and S4+ replacing Ti4+, and S2− replacing O2−, respectively. With an increase in the urea treatment time, the sulfur ions were oxidized, achieving higher valence states. S6+ substitution resulted in a charge imbalance, which could only be neutralized by hydroxide ions. The imbalance made it easier for water that had settled on the TiO2 films to chemically dissociate, and thereby generating hydroxyl radicals. OH• radicals as well as Ο2•−radicals played a significant role in the degradation of RhB dye. The RhB decolorization activity achieved by the N, S co-doped samples was 48 times that of the undoped samples.

    更新日期:2019-12-11
  • Study on factors influencing the edge slope of infrared absorption of CdZnTe crystal
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-10
    Shijin Liang, Shiwen Sun, Changhe Zhou, Chao Xu, Jiahua Min, Xiaoyan Liang, Jijun Zhang, Chengwei Jin, Haozhi Shi, Linjun Wang, Yue Shen

    When the composition of some P-type Cd0.96Zn0.04Te (CZT) crystals grown by the vertical Bridgman method (VB) is analyzed by component mapping spectrometer. It is observed that the short-wave (800–1000 nm) infrared absorption edge is inclined, accompanied by a decreased long-wave (400-4000 cm−1) infrared transmittance, which leads to an apparent interference of Zn component mapping measurement. In our research, effects of roughness, surface composition, and internal defects on the absorption edge slope of CZT (hereinafter referred to as the edge slope) were investigated by AFM, EDX, XPS and PICTS, and the main cause of non-uniformity of the slope mapping was obtained from annealing treatment. The results indicated that compared with the surface roughness and surface composition due to our surface treatment process, the dominant defect (Cd vacancy) in CZT was the principal influence factor for the edge slope, whose value was negatively correlated with the defect concentration. Furthermore, the inclination of the edge slope and the simultaneous decrease of long-wave infrared transmittance could be respectively explained by the tail state effect and the free carrier absorption caused by high-concentration Cd vacancy absorption. The mapping distribution trend of the slope presented consistency with that of the long-wave transmittance. In addition, the non-uniformity distribution of the edge slope mapping, can be effectively improved by adequate annealing under Cd atmosphere. Steep slopes and a monotonous distribution of Zn content was observed after annealing.

    更新日期:2019-12-11
  • Thermoluminescence characterization of (Ga2Se3)0.25 – (Ga2S3)0.75 single crystal compounds
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2019-12-10
    M. Isik, I. Guler, N.M. Gasanly

    Ga2Se3 and Ga2S3 compounds take attention due to their potential applications in photovoltaics. Defects and impurities may affect the quality of optoelectronic devices. Therefore, it is worthwhile to determine the parameters (activation energy, order of kinetics, frequency factor) of traps associated with the defects and/or impurities. The aim of the present paper is to investigate the trapping parameters of (Ga2Se3)0.25 – (Ga2S3)0.75 single crystal which is one of the member of (Ga2Se3)x – (Ga2S3)1-x mixed crystals. For this purpose, thermoluminescence (TL) experiments were performed on (Ga2Se3)0.25 – (Ga2S3)0.75 single crystals in the 10–300 K region. TL spectra were also recorded using various heating rates in between 0.2 and 1.0 K/s and stopping temperatures from 30 to 60 K to get the detailed information about the characteristics of the trapping parameters. TL glow curves exhibited the overlapped peaks. The stopping temperature experimental data indicated that traps present quasi-continuous distribution within the band gap. Initial rise method analyses were applied to get the activation energies of quasi-continuously distributed revealed traps. Thermal activation energies of distributed traps were found as increasing from 108 to 246 meV as stopping temperature was increased from 30 to 60 K. The structural characteristics (lattice constants and atomic compositions of constituent elements) of used compound were also reported in the present study.

    更新日期:2019-12-11
  • MEMS based Low Cost Piezoresistive Microcantilever Force Sensor and Sensor Module.
    Mater. Sci. Semicond. Proc. (IF 2.722) Pub Date : 2014-05-24
    H J Pandya,Hyun Tae Kim,Rajarshi Roy,Jaydev P Desai

    In the present work, we report fabrication and characterization of a low-cost MEMS based piezoresistive micro-force sensor with SU-8 tip using laboratory made silicon-on-insulator (SOI) substrate. To prepare SOI wafer, silicon film (0.8 µm thick) was deposited on an oxidized silicon wafer using RF magnetron sputtering technique. The films were deposited in Argon (Ar) ambient without external substrate heating. The material characteristics of the sputtered deposited silicon film and silicon film annealed at different temperatures (400-1050°C) were studied using atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The residual stress of the films was measured as a function of annealing temperature. The stress of the as-deposited films was observed to be compressive and annealing the film above 1050°C resulted in a tensile stress. The stress of the film decreased gradually with increase in annealing temperature. The fabricated cantilevers were 130 µm in length, 40 µm wide and 1.0 µm thick. A series of force-displacement curves were obtained using fabricated microcantilever with commercial AFM setup and the data were analyzed to get the spring constant and the sensitivity of the fabricated microcantilever. The measured spring constant and sensitivity of the sensor was 0.1488N/m and 2.7mV/N. The microcantilever force sensor was integrated with an electronic module that detects the change in resistance of the sensor with respect to the applied force and displays it on the computer screen.

    更新日期:2019-11-01
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