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  • Photovoltaic properties of low-damage magnetron-sputtered n-type ZnO thin film/p-type Cu2O sheet heterojunction solar cells
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-27
    Toshihiro Miyata; Hiroki Tokunaga; Kyosuke Watanabe; Noriaki Ikenaga; Tadatsugu Minami

    The photovoltaic properties of Cu2O-based heterojunction solar cells were improved using an n-type layer composed of thin films in a binary oxide semiconductor. This layer was prepared by a low-damage deposition method that applies a system for multi-chamber radio frequency (r.f.) power superimposed direct current (d.c.) magnetron sputtering. For an Al-doped ZnO (AZO)/n-ZnO/p-Cu2O heterojunction solar cell prepared using r.f. power superimposed d.c magnetron sputtering, we achieved the highest efficiency yet reported (3.22%) by optimizing sputtering conditions such as the substrate-target distance and the r.f.:d.c. power ratio. This value represents characteristics that exceed those of AZO/Cu2O solar cells having a similar structure based on r.f. power superimposed d.c magnetron sputtering.

    更新日期:2020-01-27
  • Effects of water adsorption on properties of electron-beam HfO2/SiO2 high-reflection coatings
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-27
    Tingting Zeng; Meiping Zhu; Yingjie Chai; Chaoyi Yin; Nuo Xu; Kui Yi; Yanzhi Wang; Yuanan Zhao; Guohang Hu; Jianda Shao

    The moisture-induced instability of electron-beam (e-beam) coating can even result in the performance instability of a large laser system. A dense plasma-ion-assisted-deposition (PIAD) SiO2 capping layer was employed to isolate the top surface of the coating from ambient humidity and extend the originally rapid water adsorption process, allowing a deeper understanding of the instability of e-beam coatings caused by moisture. Spectral measurements suggested that four water adsorption steps, including filling, stabilization, swelling and refilling, led to the overall redshift and short-term fluctuations in spectra. The stress and Fourier transform infrared (FTIR) analysis revealed that water adsorption and ice-like/ice structure water was responsible for the increasing compressive stress evolution at the first stage and subsequent transition from compressive to tensile stress evolution, respectively. A model based on the finite element method was proposed to calculate the water vapor transmission rate of e-beam coatings. Our study on the underlying mechanism of moisture-induced instability of e-beam coating is helpful to ensure the reliability and stability of large laser systems.

    更新日期:2020-01-27
  • Effect of absorber surface modification on the optoelectronic properties of Cu2CdGeSe4 solar cells.
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-25
    X. Li; M. Pilvet; K. Timmo; M. Grossberg; M. Danilson; V. Mikli; M. Kauk-Kuusik

    High quality Cu2CdGeSe4 micro-crystalline powder has been synthesized by molten salt method at 700°C in closed quartz ampoules using elemental Ge, binary CdSe and CuSe as precursor materials and KI as flux material. The effect of initial Cu and Cd content on the bulk composition of grown crystals was investigated. According to energy dispersive X-ray spectroscopy results, the two types of Cu2CdGeSe4 powders, with nearly stoichiometric and with Cd-rich composition were synthesized. X-ray diffraction and Raman analyses confirmed that all studied Cu2CdGeSe4 crystals had orthorhombic crystal structure. It was essential to chemically and thermally modify the surface of crystals before implementing the powder crystals as absorber materials in monograin layer solar cells. Results showed that both Br2-MeOH and HCl combined with KCN etching were effective to remove secondary phases on the crystal surface. Raman and X-ray photoelectron spectroscopy analyses revealed that after annealing at 400°C the crystal surface is covered by GexSe1-x phase, which was effectively removed by KCN etching. Using this approach, we achieved Cu2CdGeSe4 monograin layer device conversion efficiency of 5.7%.

    更新日期:2020-01-26
  • Epitaxial Ordering of Biphenyl on Aromatic Hydrocarbon Substrates
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-25
    Marissa K. Condie; Blake D. Fonda; Zackery E. Moreau; A.M. Nishimura

    A molecular adlayer of biphenyl was vapor deposited amorphously onto a single crystal of cryogenically cooled Al2O3. The biphenyl conformer at deposition was determined to be non-planar with a fluorescence λmax ∼ 320 nm. At 161 K biphenyl underwent a disorder-to-order transition which was a planar conformation analogous to the solid crystal with a fluorescence λmax ∼ 345 nm and characterized by a lower fluorescence intensity due to energy transfer. To demonstrate homoepitaxy, a molecular adlayer of biphenyl was vapor deposited and annealed above the disorder-to-order transition temperature. The thinnest adlayer for epitaxial ordering was 35 ML, monolayers, and epitaxy was achieved up to 5000 ML. Heteroepitaxy was demonstrated with p-xylene substrate with biphenyl overlayer. In addition the passage of the xylene through the biphenyl overlayer increased the density of crystalline defect sites and resulted in enhanced fluorescence intensity.

    更新日期:2020-01-26
  • Gate Capacitance Effect on P-Type Tunnel Thin-Film Transistor with TiN/HfZrO2 Gate Stack
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-24
    William Cheng-Yu Ma; Ming-Jhe Li; Shen-Ming Luo; Jiun-Hung Lin; Cai-Jia Tsai

    In this work, the polycrystalline-silicon (poly-Si) tunnel field-effect thin-film transistors (TFETs) with TiN/HfZrO2 gate stack materials are demonstrated to exhibit low threshold voltage ∼ –1.218 V, subthreshold swing (SS) ∼ 0.311 V/decade and channel length insensitive transfer characteristics. Conventional carrier transport mechanism of poly-Si thin-film transistors (TFTs) is the thermionic emission with scattering effect, which is deduced as the drift-diffusion transport model with additional trap state induced energy barrier height, resulting in the stronger channel length dependence effect. For the poly-Si TFETs, the carrier transport mechanism is the interband tunneling, including band-to-band tunneling and trap-assisted tunneling, which is less affected by the channel length. The different carrier transport mechanisms of poly-Si TFETs and TFTs would lead to different gate dielectric thickness effect. When the thickness of gate dielectric HfZrO2 is reduced from 18 to 10 nm to increase the gate capacitance density, the SS and on-state current of poly-Si TFETs exhibit much higher improvement than them of poly-Si TFTs. It indicates that the high gate capacitance density is a key parameter for the development of poly-Si TFETs to replace the conventional poly-Si TFTs in three-dimensional integrated circuit applications.

    更新日期:2020-01-24
  • Degradation behaviors and failure of magnetron sputter deposited tantalum nitride
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-24
    Ik-Soo Kim; Myung-Yeon Cho; Dong-Won Lee; Pil-Ju Ko; Weon Ho Shin; Chulhwan Park; Jong-Min Oh

    A reactive direct current magnetron sputtering method with a controlled total gas flow rate was used to fabricate thin films of tantalum nitride (TaN) on SiO2/Si and multilayer ceramic substrates. In order to identify the total gas flow rate that produced the lowest variation in the sheet resistance and the temperature coefficient of resistance (TCR), TaN films deposited under total gas flow rates of 30, 40, 60, and 80 sccm were characterized in terms of their structural and electrical properties. The optimum total gas flow rate was 60 sccm revealing the lowest deviation of sheet resistance and TCR. Next, the durability and reliability at high temperatures, after heating and cooling cycles, and exposure to induced current were tested. The degradation behaviors and failure of TaN films were investigated by measuring the sheet resistance variation. To further explain the degradation of TaN films, additional analysis of their crystallinity was conducted. The results showed that TaN-based thin film resistors have high durability and reliability and are suitable for embedded passive resistors.

    更新日期:2020-01-24
  • Crystal Quality and Surface Structure Tuning of Semi-Polar (11-22) GaN on m-plane Sapphire via In-Situ Multiple Ammonia Treatment
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-23
    Afiq Anuar; Abdullah Haaziq Ahmad Makinudin; Al-Zuhairi Omar; Ahmad Shuhaimi Abu Bakar; Azzuliani Supangat

    The crystal quality and morphological properties of semi-polar (11-22) gallium GaN were enhanced by introducing the In-Situ Multiple Ammonia Treatment (I-SMAT) method. On- and off-axis x-ray rocking curve (XRC) analysis reveals that I-SMAT would reduce several types of crystal defect namely prismatic stacking faults, basal stacking fault type I and II, and partial/perfect dislocations. By implementing an optimized flow of ammonia (NH3) and number of treated GaN pairs, the arrowhead-like features of semi-polar (11-22) GaN was effectively reduced the root mean square roughness from 4.52 to 3.07 nm. High atomic force microscopy (AFM) magnification scan demonstrated the alteration of the grain structure on the surface to become more compact and orderly arranged resulting in narrowing/shallowing of the interfacial valleys between grains. Great influence of employed I-SMAT pairs and NH3 flux was observed from XRC and AFM analysis. Conversely, excessive NH3 flux during this approach would roughen the structural and morphological properties of the semi-polar epilayer whereby the alternating thin GaN epilayer would undergo the selective-area etching to the extreme.

    更新日期:2020-01-24
  • Impact of negative bias on the piezoelectric properties through the incidence of ab-normal oriented grains in Al0.62Sc0.38N thin films
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-23
    C.S. Sandu; F. Parsapour; D. Xiao; R. Nigon; L.M. Riemer; T. LaGrange; P. Muralt

    Sputter deposited AlScN films with an Sc content of 38 at. % were investigated by X-ray diffraction and electron microscopy to study the influence of the radio frequency (RF) bias on the growth of abnormally oriented grains (AOG). Scanning electron microscopy investigations showed that the nucleation and growth of AOGs occurs with applied negative RF-bias till 4W (51 mW/cm2), while the complete loss of AOGs happens at biases larger than 6W (76 mW/cm2). The lack of AOGs within the film occurs together with the loss of the preferred (0001)-texture. At high bias powers, the (0001)-texture nucleates due to the strong (111)-texture of Pt-layer, but grain orientation becomes random during growth. The change of film microstructure with higher biases is reflected in the decay of piezoelectric properties. The concentration of trapped Ar atoms into the films increased with increasing bias power. The variation of the Ar-content along the film cross-section was ascribed to RF bias instabilities.

    更新日期:2020-01-23
  • Preparation of monoclinic Cu2SnS3 thin films by fine channel mist chemical vapor deposition method
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-23
    Kunihiko Tanaka; Mao Kowata; Fumitaka Yoshihisa; Shinya Imai; Wataru Yamazaki

    In this research, rare metal-free Cu2SnS3 (CTS) thin films were fabricated by the fine channel mist chemical vapor deposition (CVD) method, which does not require a vacuum apparatus. The mist solution was prepared by dissolving SnCl4 and CuCl2 in pure water (solvent). To obtain Cu-Sn (CT) precursor thin films by the fine channel mist CVD method, the mist solution was sprayed on alkali-free glass (Eagle) substrates heated at 390°C. The prepared CT precursor films were then heated in a sulfur-containing atmosphere (H2S (3%) + N2) to obtain CTS thin films. The X-ray diffraction patterns of the samples showed the characteristic (200), (131), (-131), and (-333) peaks of monoclinic CTS. Raman scattering spectra of the samples showed peaks in the vicinity of 292, 313, 353, and 372 cm−1, attributed to monoclinic CTS. These results showed that the deposition of monoclinic CTS by the fine channel mist CVD method was prepared.

    更新日期:2020-01-23
  • Resistive Switching Behavior and Optical Properties of Transparent Pr-doped ZnO Based Resistive Random Access Memory
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-21
    Ming-Cheng Kao; Hone-Zern Chen; Kai-Huang Chen; Jen-Bin Shi; Jun-Hong Weng; Kuan-Po Chen

    Pr-doped ZnO thin films (Zn1-xPrxO) (x = 0.00, 0.01, 0.02, 0.04) were prepared on fluorine-doped tin oxide substrates by means of the sol–gel method and spin coating technology, followed by rapid thermal annealing treatment at 800 °C. The influence of Pr content on the structural and optical properties of the Zn1-xPrxO thin film was examined and discussed. The wurtzite hexagonal structural characteristics were investigated by X-ray diffraction analysis, and Pr3+ substitution for Zn2+ ions was indicated. Finally, the typical bipolar current-voltage switching curves and electrical conduction model of Zn1-xPrxO film resistive random access memory devices were discussed and investigated for low resistance state/high resistance state in the initial forming process.

    更新日期:2020-01-22
  • Structure-sensitive principle in silicon nanowire growth
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-20
    Fengji Li; Yuehua Huang; Shu Wang; Sam Zhang

    Silicon (Si) nanowires with twining or stacking faults are challenging their applications in microelectronic devices. It is of great value to explore the assembling principle of the crystal structure of Si nanowires. In this work, Si nanowires are grown by thermal annealing of nickel (Ni) coated Si wafers underneath an amorphous carbon layer. A systematically investigation is performed on the crystal structure of Si nanowires and the connected Ni catalyst particles using field emission scanning electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction pattern. The results reveal that the defect-free Si nanowire has a highly crystalline Si core surrounded by the amorphous Si-oxide shell. Twinning and stacking faults are discovered locating near the Ni catalyst particles. The origin for the structural defects is explained by a structure-sensitive principle.

    更新日期:2020-01-21
  • Epitaxial optimization of atomically smooth Sr3Al2O6 for freestanding perovskite films by molecular beam epitaxy
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-18
    H.Y. Sun; C.C. Zhang; J.M. Song; J.H. Gu; T.W. Zhang; Y.P. Zang; Y.F. Li; Z.B. Gu; P. Wang; Y.F. Nie

    The epitaxial crystal quality of strontium aluminate (Sr3Al2O6) films under various Sr/Al ratios were systematically investigated by reactive molecular beam epitaxy. Efficient guiding rules for real-time optimization are summarized that a four-fold reconstructed reflection high-energy electron diffraction (RHEED) pattern and 4 periods of RHEED oscillations coinciding in the growth of one unit cell of Sr3Al2O6 is the key signature for the optimal growth condition. Following above rules, atomically smooth Sr3Al2O6 and freestanding SrTiO3 films with a full width at half maximum less than 0.03∘ (mainly limited by the substrates) were synthesized. The high-crystalline quality of freestanding SrTiO3 and atomically smooth interface between SrTiO3 film and Sr3Al2O6 were highlighted by the appearance of well-defined fringes from X-ray diffraction data and well-organized atomic distribution from electron microscopy. The epitaxial optimization of Sr3Al2O6 buffer layer with atomic flatness and high-crystalline quality will sheds light on the synthesis of ultrathin freestanding oxide perovskite films, paving the way to the exploration of incorporating strongly correlated properties in conventional semiconductors for a generation of multifunctional electronic devices.

    更新日期:2020-01-21
  • Wipe-on and Durable Self-cleaning Coating for Glass Facade
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-18
    Lijuan HUA; Jiawan SHEN; Yan CHEN; Qing LAN; Jie LIU

    A wipe-on self-cleaning coating based on silane has been developed, characterized, and applied on glass facades. It is a transparent, robust, and long-lasting hydrophobic coating consisted of two silane layers. The inter layer derives from a mixture of chlorotrimethylsilane and polymethylhydrosiloxane, while the outer layer derives from a mixture of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and polydimethylsiloxane. The glass samples treated with the developed coating exhibited a water contact angle of 120° and an oil contact angle of 84°, indicating excellent hydrophobic and slightly oleophobic properties. The durability of the coating has been verified via salt spray test, UV condensation, and chemical corrosion test, suggesting long-lasting properties. Its mechanical resistance properties have been evaluated by applying pencil hardness, rub, and sandblasting tests. Corresponding results demonstrated the excellent anti-scratch properties of the developed coating. All the outstanding performances of the developed coating ensure its potential commercial application for glass facades.

    更新日期:2020-01-21
  • Thickness Estimation of the Silica-Like Thin Layers via Swelling-Driven Wrinkling Instability
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-17
    Ha Ryeong Cho; Dooho Choi; Myunghwan Byun

    In the present study, we report a simple, yet facile route to thickness characterization of the UV/ozone (UVO) treated polydimethylsiloxane (PDMS) thin layer via osmotically-driven wrinkling instability. Through the UVO oxidation process of PDMS, a bi-layered film with local moduli-mismatch regions (i.e., the top UVO exposed region of a thin stiff (less-elastomeric) SiOx layer and the bottom region of an unmodified, elastomeric PDMS foundation) was generated. When ethanol directly dropped on top of a bi-layered film and swelled preferentially a lower elastomeric PDMS foundation, the wrinkles were produced in the confined area within the three-phase contact trace of the ethanol droplet, and then vanished completely as the ethanol evaporated irreversibly. The wrinkle wavelength was observed to be magnified as the mixing ratio of base monomer and curing agent increased from 7:1 to 8:1 to 9:1 to 10:1. The increasing wavelength as a function of increasing UVO treatment time (tUVO) reflected increasing thickness of the silica-like layer. For a given ratio, the SiOx thickness was found to increase similarly to the wrinkling wavelength as the tUVO increased. The thickness varied from 22.3 ∼ 43.4 nm to 51.1 ∼ 99.3 nm as the tUVO varied from 12 min to 60 min. A hydrophobic recovery of a hydrophilic thin SiOx film created by UVO treatment was observed by examining the wrinkle wavelength as a function of elapsed time. As time passed by, a decrease in the wrinkle wavelength confirmed the hydrophobic-to-hydrophilic transition.

    更新日期:2020-01-17
  • Electrophoretic deposition of hydroxyapatite-iron oxide-chitosan composite coatings on Ti-13Nb-13Zr alloy for biomedical applications
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-16
    Sandeep Singh; Gurpreet Singh; Niraj Bala

    In this study iron oxide (Fe3O4) incorporated hydroxyapatite (HA) and chitosan (CS) composite coatings were developed to enhance the corrosion resistance and surface properties of Ti-13Nb-13Zr alloy. Pure HA and composites with different percentage (1, 3 and 5%, wt %) of Fe3O4 have been fabricated by using the electrophoretic deposition method (EPD). The morphology of the composite coating indicated porous nature with average 10 ± 0.2 µm coating thickness, were examined by scanning electron microscopy (SEM). The wettability behavior and surface roughness values of the composite coatings were measured and discussed. The Electrochemical test was performed to evaluate the corrosion behavior in Ringer's solution. TheHA-1wt% Fe3O4 composite coating exhibited the preeminent corrosion resistance with lowest Icorr and the highest Ecorr value as a contrast to HA-3wt% Fe3O4 and HA-5wt% Fe3O4 coatings. Additionally, in vitro bioactivity test were conducted in Ringer's solution for 7 days. It was found that the composite coating enhanced the apatite formation ability, which was further endorsed by SEM-EDX analysis. In conclusion, the composite HA-CS bioactive coating incorporated with Fe3O4 is proposed as a promising candidate for biomedical applications.

    更新日期:2020-01-16
  • Synthesis of co-sputter deposited Ni-Ti thin alloy films and their compositional characterization using depth sensitive techniques
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-15
    V. Karki; A.K. Debnath; S. Kumar; Debarati Bhattacharya

    Ni-Ti (Nickel-Titanium) thin alloy films of different concentration and thickness were synthesized using magnetron co-sputtering process utilizing separate Ni and Ti targets. Concentrations of Ni and Ti in the deposited films were optimized by controlling the power ratio of individual Ni and Ti targets. Thickness and density of the layered structures present in the films were evaluated by X-ray Reflectivity (XRR). Atomic concentrations of Ni and Ti were determined by Energy Dispersive X-ray Spectroscopy and matched with the concentrations obtained through XRR measurements. Secondary Ion Mass Spectrometry and Rutherford Backscattering Spectrometry were utilized to investigate the elemental depth distributions of Ni, Ti and O content in the films. Depth distribution studies confirmed that oxygen as a surface contaminant was present in all the deposited films, although films having thickness in the range of 21.5 nm - 22.7 nm, were found to contain oxygen within the films too. Thicker Ni-Ti alloy films, in the range of 51.3 nm - 52.3 nm, did not reveal any oxygen contamination in the bulk of the films. X-ray Photoelectron Spectroscopy (XPS) was used to determine elemental and molecular content of the deposited films. XPS analysis confirmed the presence of NiO at the surface and intermetallic Ni-Ti within the deposited films.

    更新日期:2020-01-15
  • Fabrication of a Plasma Electrolytic Oxidation/Anodic Aluminum Oxide Multi-Layer Film via One-Step Anodizing Aluminum in Ammonium Carbonate
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-14
    Tatsuya Kikuchi; Taiki Taniguchi; Ryosuke O. Suzuki; Shungo Natsui

    A plasma electrolytic oxidation (PEO)/anodic aluminum oxide (AAO) multi-layer film was fabricated via one-step galvanostatic anodizing of high-purity aluminum in 0.3-2.0 M ammonium carbonate ((NH4)2CO3) solutions at 283-333 K and 25-400 Am−2. Anodizing at higher concentrations and higher temperatures caused the formation of relatively uniform anodic oxide film on the aluminum substrate. Characteristic voltage-time curves with two high-plateau voltages at approximately 250 V and 375 V were obtained during galvanostatic anodizing. A multi-layer structure of an outer PEO layer with a crystalline γ-Al2O3 structure and an inner amorphous AAO layer with nano-cylinerical pores was formed by continuous visible sparking occurring after passing the first voltage plateau region. The whole aluminum surface was covered with the multi-layer structure after reaching the second voltage region. The thickness of the multi-layer increased with time via the further anodizing process at the second plateau voltage. Pore sealing of the inner nanoporous film was achieved by immersion post-treatment in boiling water.

    更新日期:2020-01-14
  • Understanding the effects of electric-field-induced phase transition and polarization loop behavior on the energy storage performance of antiferroelectric PbZrO3 thin films
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-11
    Minh D. Nguyen; Trang T. Trinh; Ha T. Dang; Hung N. Vu

    Antiferroelectric PbZrO3 (PZO) thin-films were fabricated by pulsed laser deposition (PLD) and sol-gel techniques to investigate the effect of antiferroelectric-ferroelectric (AFE-FE) phase transition on the energy storage performance. The (100)-oriented PLD thin-films have a square-double polarization-electric field (P-E) hysteresis loop with a sharp-phase transition and the (111)-oriented sol-gel thin-films have a slanted P-E loop with a diffused-phase transition. The difference in the phase transition fields between PLD and sol-gel thin-films could be attributed to their difference in crystalline orientations. In this case, the antipolar AFE phase is along the [110]-direction of the original tetragonal-cell under zero electric-field, while the antipolar AFE phase switches into the polar FE phase under a strong enough electric-field and the tetragonal-cell becomes rhombohedral with the polar direction of [111]. Due to the larger maximum polarization and slimmer P-E loop, the higher recoverable energy-storage (Ureco) of 19.4 J/cm3 and larger energy-efficiency (η) of 70.8%, are achieved in sol-gel thin-films. More importantly, this film shows excellent charge-discharge cycling endurance of both Ureco and η values after 1010 cycles and good thermal-stability under a wide operating temperature. From the viewpoint of applications, the sol-gel method is considered to be a promising approach towards producing low-cost PZO thin-films for high-efficiency energy-storage devices over a broad temperature range.

    更新日期:2020-01-13
  • Broadband photoresponse of flexible textured reduced graphene oxide films
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-11
    Hee Yeon Yang; Hyun Joo Lee; Yongseok Jun; Yong Ju Yun

    Herein, we fabricated flexible and transparent textured graphene films based on reduced graphene oxide flakes on polyethylene terephthalate substrates using a spray coating technique and investigated their photoresponsivity over a broadband range of wavelengths from the ultraviolet to infrared regions. The fabricated films exhibited a broadband photoresponse, with responsivity values reaching 2.5 mA/W at 365 nm, 2.4 mA/W at 530 nm, and 1.7 mA/W at 940 nm. In addition, the photoresponsivity was studied under bending deformation. Our flexible and textured reduced graphene oxide films could maintain a stable photoresponse upon bending for the radii of curvature larger than ∼ 0.35 cm with a photocurrent deviation of <10% in the infrared range. The broadband photoresponse with good flexibility and transparency suggests that the reduced graphene oxide films can have immense potential for applications in flexible optoelectronic technologies.

    更新日期:2020-01-13
  • nAnisotropic Biaxial Stress Evaluation in Metal-Organic Chemical Vapor Deposition Grown Ge1-xSnx Mesa Structure by Oil-Immersion Raman Spectroscopy
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-10
    Kazutoshi Yoshioka; Ryo Yokogawa; Atsushi Ogura

    Germanium tin (Ge1-xSnx) is one of the most promising materials for various types of electronic devices, optoelectronic devices and so on. From the application view point, the stress induced in the Ge1-xSnx significantly modifies the band structure, therefore affects both the electric and optical performances. Moreover, the stress in the actual device is typically in complicated anisotropic biaxial manner rather than simply isotropic or uniaxial. However, it is difficult to evaluate the precise stress states. In this study, we investigated the dependence of pattern size of the Ge1-xSnx mesa structure on the anisotropic biaxial stress by oil-immersion Raman spectroscopy. We verified that stress relaxation progresses sufficiently due to the nano-fabrication process. From the results, it was confirmed that the behavior of uniaxial stress relaxation in the Ge1-xSnx mesa structure is depending on the pattern size.

    更新日期:2020-01-10
  • Origins of thin film delamination induced by electrodeposition and processing methods to overcome it
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-10
    Longchang Ni; Ryan M. Pocratsky; Maarten P. de Boer

    Electrodeposition is widely used to deposit films in technological applications, but when the current efficiency is low, injected hydrogen can strongly affect the materials properties of an underlying film including its residual stress, adhesion and electrical resistivity. It is of interest to quantify this issue and demonstrate processing routes that retain good quality films. In this work, we explore the effects of electrodeposited nanocrystalline Ni-W on to a Ta thin film. This system serves as challenging test case because the current efficiency is only 31%. We observe that H incorporation induces GPa-level compressive stress in an underlying Ta film. The stress initiates a buckling-induced delamination failure of within 2 s, even though at 1.5 µm the Ta is relatively thick. Delamination over the entire film area occurs within 5 s. We demonstrate two process routes by which Ta films remain adhered when Ni-W is electrodeposited for 100 s, corresponding to a 1 µm thick Ni-W film.

    更新日期:2020-01-10
  • Energy, temperature, and deposition angle dependence of Cd and Te2 deposited on CdTe
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-10
    Indiras Khatri; Jacques Amar

    Cadmium Telluride (CdTe) is an important material for the production of high-efficiency thin-film solar cells. While sputter deposition has been used to create CdTe-based solar cells, two other important methods of growth are close-spaced sublimation and vapor deposition. In these methods, the depositing clusters correspond to Cd atoms and Te2 dimers while the deposition energies are relatively low. In addition, depending on vapor pressure, deposition method, and target-substrate distance, deposition may occur at relatively large angles with respect to the substrate normal. Here we investigate the dependence of the attachment probability and deposition site for Cd and Te2 clusters deposited on Cd-terminated and Te-terminated (100) and (111) surfaces of zincblende CdTe on deposition conditions. In general, we find that the deposition of Cd atoms and/or Te2 dimers on the oppositely terminated surface leads to an attachment probability which is close to 1 and relatively independent of deposition conditions for both the (100) and (111) orientations. In contrast, deposition on the same terminated surface leads to a significantly lower attachment probability which generally decreases with increasing deposition angle, energy, and substrate temperature. Our results also indicate that deposition on the (111) surface leads to a significant excess Te sticking probability. In contrast, the excess Te attachment probability for deposition on the (100) surface is typically significantly smaller, and in some cases may even be negative. We also find, for both deposition on the (111) surface as well as opposite termination deposition on the (100) surface, that the dominant deposition mode corresponds to sitting on top of the surface which corresponds to growth of the next layer. In contrast, for same termination deposition on the (100) surface the dominant deposition mode corresponds to joining the first layer. These results imply that even for low deposition energies and substrate temperatures, deposition on the (100) surface is likely to create interstitials in the surface layer.

    更新日期:2020-01-10
  • Microstructure and mechanical properties of TiSiNiN nanocomposite films
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-10
    Haoming Du; Ping Liu; Wei Li; Ke Zhang; Fengcang Ma; Xinkuan Liu; Xiaohong Chen; Daihua He

    A series of quarternary TiSiNiN nanocomposite films with the different Si and Ni content are prepared by reactive magnetron sputtering technique. The effects of the Ni/Si content ratio on the microstructure and mechanical properties of the TiSiNiN nanocomposite films were investigated by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and nanoindentation techniques. When the Ni/Si content ratio is 1:4, the TiSiNiN nanocomposite film is remarkably hardened with the maximal hardness and elastic modulus 48.6 GPa and 550 GPa, respectively. The hardened TiSiNiN film is characterized as the nanocomposite structure with the TiN nanocrystallites surrounded by the (Si3N4+Ni) crystallized interfacial phase. The enhancement in the hardness and elastic modulus of the TiSiNiN nanocomposite film can be explained by the joint effects of the difference in the shear moduli, the alternating-stress strengthening mechanism, and the Hall-Petch relation theory, which can be expressed as a "nc-TiN/c- Si3N4/c-Ni" model.

    更新日期:2020-01-10
  • Photocurrent decay from the steady-state in thin film hydrogenated amorphous silicon: numerical simulation analysis of experimental results
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-07
    Javier A. Schmidt; David M. Goldie

    Starting from the multiple trapping rate equations that define the non-equilibrium concentrations of electrons and holes in extended states, the experiment of photocurrent decay from the steady-state is examined. A system of non-linear coupled differential equations is solved to get the temporal evolution of the occupation functions and the carrier concentrations after cessation of the illumination. Different expressions proposed in the literature to evaluate the carrier lifetimes from the photocurrent decay data are critically examined. Measurements performed on a series of hydrogenated amorphous silicon samples deposited at different substrate temperatures are reproduced by the simulations. It is found that the response time determined from the photocurrent initial rate-of-decay provides an excellent estimation of the free lifetime of the majority carrier, provided the decay is recorded from sufficiently short times. It is also found that the common recombination lifetime can also be estimated from the photocurrent decay data.

    更新日期:2020-01-07
  • Performance Enhancement of Perovskite Solar Cells via Modification of the TiO2/Perovskite Interface with Oxygen Plasma Treatment
    Thin Solid Films (IF 1.888) Pub Date : 2020-01-07
    Yumeng Wang; Dongdong Wang; Hao Qu; Jiushan Cheng; Yi Fang; Chunmei Zhang; Qiang Chen

    High-temperature (∼500 °C) sintering is a routine post-treatment to fabricate compact Titanium dioxide (TiO2) electron selective layer (ESL) in high-performance perovskite solar cells (PSCs). Here, we propose an effective low-temperature (<150 °C) approach: pinhole-free and compact ultrathin TiO2 layers are fabricated via thermal atomic layer deposition (ALD) following a low-pressure oxygen plasma treatment. The hydrophilicity of TiO2 surfaces can be suitably tailored, which favors precursor solution being well spread and the growth of perovskite film. In addition, effective removal of oxygen vacancies serving as unproductive quenching sites in TiO2 surface is observed, which is attributed to atomic oxygen radical, the most reactive species generated in oxygen plasma. The PSC device with oxygen-plasma-treated ALD-TiO2 ESL achieves an efficiency of 14.9%, which is better than 13.3% of the device with 500 °C- sintered ALD-TiO2 ESL and comparable to 14.3% of the device with conventional 500 °C-sintered Sol-gel-TiO2 ESL under our conditions.

    更新日期:2020-01-07
  • Effect of lattice deformation on electronic and optical properties of CuGaSe2: ab-initio calculations
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-31
    M. Bikerouin; M. Balli; M. Farkous; M. El-Yadri; F. Dujardin; A. Ben Abdellah; E. Feddi; J.D. Correa; M.E. Mora-Ramos

    In this study, we have investigated the effect of bi-axial, ϵab, and uni-axial, ϵc, strains on the optoelectronic properties of chalcopyrite semiconductor CuGaSe2 through first-principles full potential linearized augmented plane wave method. These materials have recently attracted much interest within the materials science community. The results are obtained in the framework of Density Functional Theory (DFT), using the Generalized Gradient Approximation based on the minimization of total energy, together with the modified Becke-Johnson exchange-correlation potential, as implemented in the WIEN2k code. Our results show that unstrained CuGaSe2 is a direct band gap semiconductor with a energy of 1.16 eV, thus improving the results of some previous DFT calculations, but still below the accepted experimental data. The incorporation of biaxial and uniaxial strain results in a monotonous decreasing behavior of the energy band gap when both ϵab and ϵc change between -8% and +8%, with unstrained value being, approximately, at the middle of the variation range. It is also found that strain causes modifications in the index of refraction of the material, with modifications of its static value that rank above 10% over the entire range of deformations considered.

    更新日期:2019-12-31
  • Balancing charge-transporting characteristics in bipolar host materials
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-31
    Kyu Sung Kim; Dong Uk Kim; Kuk Soung Joung; Jae-Woong Yu

    Bipolar host materials with balanced charge transporting property were synthesized using a solvent-less green reaction method. The characteristics of these synthesized bipolar host materials were examined by thermal and spectroscopic analysis. The energy levels of these materials were estimated from cyclic voltammograms and absorption spectra. The optimized molecular geometries and spatial distributions were obtained from molecular simulations. Moreover, the current density vs. voltage features of single-carrier devices were investigated to assess the bipolar transport characteristics of the host materials. As the length of the alkyl chain increased, the electron-transporting capability and hole-transporting ability exhibited optimum values at the octyl chain attachment. The current efficiency, power efficiency and quantum efficiency values of white organic light-emitting diodes prepared by blending blue and yellow iridium phosphors with these bipolar hosts were high with decreasing alkyl chain length. The result was remarkably similar to the trend of current density characteristics of single-carrier devices. The power efficiency of the octyl chain attached bipolar host was approximately three times higher than that of typical blended hole and electron transporting materials. This enhanced efficiency was attributed to the well-balanced charge transfer by the bipolar host material inside an emissive layer. Moreover, the morphology of the device fabricated with a blend of charge transport materials changed due to deterioration, whereas that of the device fabricated with bipolar host materials did not change after 12 h of operation at 9 volts.

    更新日期:2019-12-31
  • Annealing Dependence of Structural and Optical Properties of Zr-doped ZnO Films Deposited by Radio Frequency Magnetron Co-sputtering
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-30
    Nark-Eon Sung; Matthew A. Marcus; Kug-Seung Lee; Hyung Joong Yun; Ik-Jae Lee

    To examine the effects of annealing temperatures, Zr-doped ZnO (Zn1-xZrxO1+δ; ZZO) thin films with x = ∼0.067 were deposited at room temperature by radio frequency co-sputtering on quartz substrates and annealed in air at 300 °C, 400 °C, 500 °C, respectively. Annealing dependence of ZZO films was investigated by using X-ray diffraction, atomic force microscope X-ray absorption fine structure (XAFS), ultraviolet-visible (UV-Vis) spectroscopy, and resistivity. The results show that ZZO films maintain a strong preferred orientation toward c-axis, but the size of crystallites increased and the surfaces of the ZZO films were roughened with increasing annealing temperature. The Zn atoms were in divalent state and slightly affected by annealing, but Zr atoms were tetravalent and the spectra were slightly different from that of ZrO2. The variance of the Zn-O distance distribution, probed by polarization-dependent K-edge XAFS, in the ab-plane was stronger than that of the c-axis. The optical transmission spectra at 200 ≤ λ ≤ 900 nm showed high transparency of ≥ 90%, decrease of optical band gap, and red-shift as temperature increased. The resistivity decreased with enormously with increasing temperature. These results are ascribed to the increase of grain size.

    更新日期:2019-12-31
  • Control of microstructure in polymer:fullerene active films by convective self-assembly
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-30
    Otto Todor-Boer; Ioan Petrovai; Raluca Tarcan; Leontin David; Simion Astilean; Ioan Botiz

    It is nowadays accepted that optoelectronic properties of the donor-acceptor active layers are microstructure dependent and can be manipulated by employing various film deposition techniques. In this work, we show that fully intercalated co-crystalline polymer:fullerene microstructure can be obtained when depositing thin films using convective self-assembly technique. Moreover, this microstructure appears to be dependent, under specific film casting conditions, on the fullerene size. Use of slightly bigger fullerenes is leading to a multi-phase microstructure comprised of neat polymer domains, fullerene aggregates and co-crystalline polymer:fullerene structures.

    更新日期:2019-12-30
  • Heater-assisted intense pulsed light irradiation for lanthanum strontium cobaltite thin film electrode fabrication
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-28
    Jun-Sik Park; Hojae Lee; Suhaeng Heo; Young Beom Kim

    This study describes the bottom-heater-assisted flash light irradiation method for fabrication of lanthanum strontium cobaltite (La0.6Sr0.4CoO3−δ, LSCO) thin films. Unlike the conventional sintering process, flash light irradiation proceeds instantly under ambient conditions. Since the flash light irradiation process involves the photothermal effect, heat energy supplied by a bottom heater can compensate for decreased irradiation energy. The substrate temperature was varied from room temperature to 200∘C and 300∘C, and the radiation energy requirement for obtaining an optimized LSCO film was decreased with increasing temperature. In addition, the instantaneous temperature difference due to highly intense energy between the top surface and the substrate can be relieved. With the innovative sintering system, an electrolyte-supported solid oxide fuel cell could be fabricated by the flash light irradiation method, and electrochemical characterization of the fuel cells was conducted.

    更新日期:2019-12-29
  • Forming Si nanocrystals on insulator by wet anisotropic etching
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-24
    M.A. Zrir; M. Kakhia; N. AlKafri

    Implementing the Silicon-On-Insulator platform, we reveal an approach to fabricate Si nanocrystals on insulator by a single step, wet anisotropic etching of thin crystalline layers. The evolution of the Si layer was investigated from the onset of the dissolution process up to the development of isolated nanocrystals. Our results also provide several insights into the understanding of the early stages of the hillocks formation characteristic for the anisotropic etching of Si(001). We discuss several related mechanisms and we give experimental evidences that support the stabilization of the pyramidal hillocks apices by short-lived silicate particles.

    更新日期:2019-12-25
  • Investigations on post sulphurised Cu2ZnSnS4 absorber layer thin films prepared using Radio Frequency Magnetron Sputtering
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-19
    G. Balaji; N. Prabavathy; R. Balasundaraprabhu; S. Prasanna; Elena Echeverria; D.N. McIlroy; K. Sivakumaran; M.D. Kannan; Dhayalan Velauthapillai

    Copper zinc tin sulfide (CZTS) quaternary semiconductor thin films were prepared using binary sulfur rich sputtering targets - copper sulfide (CuS), zinc sulfide (ZnS), and tin sulfide (SnS) by Radio Frequency Magnetron Sputtering with the stacking sequence CuS/ ZnS/ SnS at a substrate temperature of 300 ⁰C. The films were then subsequently sulphurised at 350 ⁰C in Hydrogen Sulfide atmosphere for 60 minutes. X-ray diffraction studies carried out on the CZTS films revealed the presence of CZTS kesterite phase along the <112> and <220> directions. X- ray diffraction results were validated by Raman spectroscopy. The composition of CZTS thin films were confirmed using X-Ray photoelectron spectroscopy and the atomic percentage of the individual elements were quantitatively estimated. The Valance band spectra and Ultra-violet photoelectron spectroscopy were used to study the electronic properties of the sulphurised CZTS thin films. The optical properties of CZTS thin films were studied using Ultraviolet - visible spectrophotometer and the optical band gap was found to be 1.477 eV. The Hall Effect measurements confirmed the p-type nature of the films and the results are discussed.

    更新日期:2019-12-19
  • Broad emission spectral enhancement of polyfluorene copolymer by coupling to assembled plasmonic crystal of silver nanocubes
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-19
    Donglin Yuan; Hanmei Li; Weiwei Zhu; Futao He; Yuanqing Xu; Xianrui Meng; Wenkai Zhang; Xiaomin Fang; Tao Ding

    The plasmonic enhancement of conjugated polymer (CP) based light-emitting device calls for large scale and high quality plasmonic crystals (PlCs). Herein, silver nanocubes with diameters of 55 nm and 100 nm have been respectively assembled into closely packed PlC-55 and PlC-100 through oil-water interfacial assembly method. By coupling with the PlCs, the photoluminescence (PL) of polyfluorene copolymer can be enhanced in a broad range of excitation and emission wavelengths, exhibiting over 10-fold enhancement in PL intensity as the PlC-CP separation is controlled at 11 nm by using polyvinylalcohol as a spacer. The Purcell factors of CPs show both particle size and emission wavelength dependence, where the maximum value of 4.5 are found in CPs that are placed on PlC-100 at wavelengths near the CP emission peak.

    更新日期:2019-12-19
  • Determination of the width of the density of states of the Highest Occupied Molecular Orbital in Pentacene
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-19
    Sanjoy Jena; Debdutta Ray

    We present a simple and effective method to estimate the width (σ) of the density of states (DOS) of the Highest Occupied Molecular Orbital (HOMO) in pentacene using field effect studies. This method can be applied to most organic semiconductors where charge carrier motion is by thermally activated hopping. The charge carrier density dependent mobility acts as the probe. We show from simulations that the variation of mobility, as a function of charge carrier density, is highly sensitive to σ. Thus, σ can be found with low error using this method. We optimize the fabrication process to develop pentacene transistors with greatly diminished non-idealities. We estimate the width of the DOS of the HOMO for pentacene to be 80 ± 10 meV. The contribution of the tail states is explored and we find it to be negligible in the on-state of the transistors studied.

    更新日期:2019-12-19
  • Control of the chemical composition of silicon carbon nitride films formed from hexamethyldisilazane in H2/NH3 mixed gas atmospheres by hot-wire chemical vapor deposition
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-18
    Yūki Katamune; Hiroto Mori; Fumihiro Morishita; Akira Izumi

    Silicon carbon nitride (SiCN) films were deposited by hot-wire chemical vapor deposition using hexamethyldisilazane (HMDS) as the single source gas diluted in ammonia (NH3) and hydrogen (H2) gas mixtures. The chemical composition of the SiCN films was controlled by adjusting the NH3/H2 flow rate ratio. X-ray photoelectron spectroscopy measurements revealed that the carbon and nitrogen contents of the films were controllable from 10 to 35 at. %, while the silicon content remained almost constant at 45 at. %. Although the homogeneity of the SiCN films deposited using HMDS diluted only with H2 degraded with increasing stage temperature from 400 to 800°C, it was improved by replacing H2 with NH3. Upon introducing NH3, the nitrogen content increased as carbon content decreased accompanied by the replacement of Si−C and C−C bonds by Si−N, N−H, and C−H bonds, which led to the deterioration of the mechanical properties of the SiCN films.

    更新日期:2019-12-19
  • OPTICAL AND ELECTRICAL PROPERTIES OF Ti SUBOXIDES GROWN BY REACTIVE GRID-ASSISTED MAGNETRON SPUTTERING
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-18
    Heitor Wilker Silva Barros; Diego Alexandre Duarte; Julio César Sagás

    In this paper, the structural, optical, and electrical properties of titanium suboxides (TiOx) are investigated. The sub-stoichiometric films were obtained by grid-assisted magnetron sputtering in an atmosphere of Ar and O2 at different oxygen concentrations in gas flow rate. The samples were characterized by profilometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The optical and electrical properties were measured by optical spectrophotometry and the van der Pauw method, respectively. Oxygen deficiency (x < 2) decreases the film resistivity without doping with other elements and shifts the absorbance to longer wavelengths, in consequence of a second optical gap in the TiOx films. The optical properties can be controlled, changing the visual aspect of the films from “mirror-like” to transparent, through opaque yellow and bluish films.

    更新日期:2019-12-19
  • Including substrate temperature in berg model FOR reactive sputtering
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-18
    Júlia Karnopp; Julio César Sagás

    Reactive magnetron sputtering deposition can be qualitatively simulated by the well known Berg model. However, such model does not take into account explicitly the dependence of the substrate temperature on the sticking coefficient. The substrate temperature plays a major role in film properties and also affects the hysteresis curves. In order to analyze the effect of substrate heating on the hysteresis curves, the Berg model equations were rewritten by using both the Langmuir and the Kisliuk adsorption models. The theoretical results show that a raise on substrate temperature causes variations in the first critical point, but the adsorptions models exhibit different temperature dependences. In the experimental hysteresis curves obtained for Ti and Al targets using N2 and O2 as reactive gases, the effects of substrate temperature are very small, therefore, negligible.

    更新日期:2019-12-18
  • Brown coloration and electrochromic properties of nickel doped TiO2 thin films deposited by nebulized spray pyrolysis technique
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-12
    T. Dhandayuthapani; R. Sivakumar; R. Ilangovan; C. Sanjeeviraja; K Jeyadheepan; C. Gopalakrishnan; P. Sivaprakash; S. Arumugam

    Titanium dioxide (TiO2) is a promising candidate for electrochromic smart window and energy applications. In the present work, an eco-friendly approach to spray deposition technique was used to deposit undoped and nickel doped TiO2 thin films using glycerol as an additive. The effect of nickel doping on the microstructure, morphology, composition, magnetic, and electrochromic properties of TiO2 was investigated in detail. Under the action of negative voltage, the undoped TiO2 films exhibit blue coloration, whereas, the nickel doped TiO2 films exhibit brown coloration due to Ni2+ induced defects. The 6% nickel doped TiO2 film achieved a high reversibility of 82% and high transmittance modulation of 48.5%, with a colouration efficiency of 267 cm2/C, fast response of 2.3 s for colouration and 2.5 s for bleaching, compared to other nickel doped TiO2 films.

    更新日期:2019-12-13
  • Titanium oxynitride films for surface passivation of crystalline silicon deposited by plasma-enhanced atomic layer deposition to improve electrical conductivity
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-12
    Eun-Jin Song; Hyunjin Jo; Se-Hun Kwon; Ji-Hoon Ahn; Jung-Dae Kwon

    For achieving improved electrical conductivity through surface passivation of crystalline silicon, we investigated TiON films by combining TiO2 and TiN deposition cycles in plasma-enhanced atomic layer deposition. To control the composition of the TiON films, a super-cycle—composed of one cycle of TiO2 and x-cycles of TiN—was adopted. The thickness of the films could be precisely controlled on the nanometer and sub-nanometer scale, regardless of the TiO2:TiN sub-cycle ratio. The chemical state, crystalline phase, and interface characteristics of the TiON films were examined. For the TiO2:TiN = 1:20 film, the carrier lifetime was increased from 30 to 243 μs, while the resistivity decreased from 3.1 × 108 to 7.1×10−1 Ω•cm compared to the TiO2 film.

    更新日期:2019-12-13
  • Influence Of Generation Control Of The Magnetron Plasma On Structure And Properties Of Copper Nitride Layers
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-11
    Katarzyna Nowakowska - Langier, Lukasz Skowronski, Rafał Chodun, Sebastian Okrasa, Grzegorz W. Strzelecki, Magdalena Wilczopolska, Bartosz Wicher, Robert Mirowski, Krzysztof Zdunek

    This paper describes one of the series of works that aimed to investigate the impact of modulation frequency. This parameter is specific to plasma excitation and is associated with the properties of the thin films of copper nitride synthesized by magnetron sputtering. The studies reported in this paper focus on the changes in chemical and phase compositions of the Cu-N layers with respect to their electronic properties. The measurements obtained allowed studying the phenomena that occur during the synthesis of the metastable copper nitride. The results revealed that the synthesis processes are very sensitive to changes in sputtering parameters. It was also found that the modulation of sputtering frequency and the power influence the structure and consequently the properties of the synthesized layers.

    更新日期:2019-12-11
  • SiC-conversion coating from silica sol for improved oxidation resistance of carbon-fiber insulator in solar-cell ingot-growing crucibles
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-10
    Su-Bin Ahn, Minh Dat Nguyen, Jung-Won Bang, Younghee Kim, Yoonjoo Lee, Dong-Geun Shin, Woo-Teck Kwon

    Carbon fibers, which have excellent mechanical and thermal properties, are used in many fields; however, they are very vulnerable to oxidation and have limited service life. Various studies have attempted to address this. In this study, a SiC–C composite material was prepared using a silica sol to coat the carbon surface and improve the oxidation resistance of a carbon-fiber insulator as a material for solar-cell ingot-growing crucibles. The SiC coating was formed on the carbon surface under various conditions by controlling the composition of the silica sol, and its characteristics were examined. Via SiC-conversion coating through a carbothermal reaction, a film of thickness 30–80 nm film was uniformly formed over the entire sample. In addition, the oxidation characteristics were enhanced by a factor of three to five, when compared with conventional carbon materials.

    更新日期:2019-12-11
  • Nonlinear Elasticity in a Meta-Film Comprising Nano-Helices
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-10
    Ryota Kaneko, Tetsuya Yukishita, Takashi Sumigawa, Takayuki Kitamura

    The aim of this study is to fabricate a meta-film exhibiting nonlinear elastic behavior on the basis of the significant deformability of spring-shaped nano-helices using glancing angle deposition. The unique mechanical properties of this film were examined by extracting a single nano-helix and examining this element using in situ electron microscopy while applying a tensile load. The helix showed nonlinear reversible behavior and the relationship between load, F [nN], and displacement, δ [nm], was determined to be F = 4.1δ + 0.0041δ2. A nonlinear finite element analysis confirmed that this nonlinearity originated from the large deformation permitted by the spring shape. Both the stiffness and degree of nonlinearity of the meta-film could potentially be adjusted over a wide range by modifying the geometry and the density of the nano-helices.

    更新日期:2019-12-11
  • Strain Control of Phase Transition and Magnetic Property in Multiferroic BiFeO3 Thin Films
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-09
    Wanchao Zheng, Dongxing Zheng, Dong Li, Peng Li, Linxing Zhang, Junlu Gong, Xin Pang, Chao Jin, Xixiang Zhang, Haili Bai

    BiFeO3 (BFO), a room-temperature antiferromagnetic-ferroelectric multiferroic, is widely researched due to its potential applications for electric-field control of the magnetism. In this work, the strain control of the phase transition and magnetic properties in the BFO/LaAlO3 heterostructures were investigated. The O K edge polarization-dependent X-ray absorption spectroscopy (XAS) spectra show that the Fe 3d level splits into five levels, which proves that the FeO5 pyramid is asymmetric in the highly strained tetragonal-like BFO. The spin canting induced by the asymmetric structure leads to the magnetic moment. Thus, an obvious magnetic signal in the 17-nm-thick BFO thin films was observed by the Quantum Design magnetic property measurement system. With the increase of the BFO film thickness, the clamping effect induced by the substrate becomes weak, further leading to the BFO phase transition. The O K edge polarization-dependent XAS spectra demonstrate that the orbital reconstruction exists at the mixed BFO phase boundaries. Since the orbital reconstructions can induce the strong magnetic coupling, the magnetic order of the different BFO phases will be coupled with each other. It causes a variation of the magnetic property at the phase boundaries or in the BFO phases.

    更新日期:2019-12-11
  • Influence of the Pt thickness on the structural and magnetic properties of epitaxial Fe/Pt bilayers
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-09
    D. Karfaridis, L. Mihalceanu, S. Keller, K. Simeonidis, G.P. Dimitrakopulos, Th. Kehagias, E.Th. Papaioannou, G. Vourlias

    Interface induced phenomena in layered magnetic/non-magnetic structures have led to big discoveries, such as giant magnetoresistance, which has defined the field of spintronics. Interfaces are capable of inducing magnetism even in non-magnetic layers, like platinum. Here, we investigated the static magnetic properties of modified interfaces in Fe/Pt bilayers, deposited on MgO substrates via an electron beam evaporation technique. We show the impact of the thickness reduction of the non-magnetic material, from 18 nm down to 1 nm, on the structural and magnetic properties of the epitaxial Fe/Pt bilayers. Below a platinum thickness of 6 nm a significant increase of the magnetic hardness and a uniaxial anisotropy is observed. We correlate the magnetization reversal with the increase of the elastic strain of the Pt layer, in conjunction with the interfacial Fe/Pt roughness and Pt proximity effect, which is enlarged as the Pt thickness is decreased.

    更新日期:2019-12-09
  • Optical Characterization of type-II ZnO/ZnS Multiple Quantum Wells grown by Atomic Layer Deposition
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-06
    Mostafa Afifi Hassan, Aadil Waseem, Muhammad Ali Johar, Sou Young Yu, June Key Lee, Jun-Seok Ha, Sang-Wan Ryu

    ZnO/ZnS multiple-quantum wells (MQWs) were grown on Si substrates by atomic layer deposition, and their optical properties were investigated. Light emission well below the band-to-band transition energies of constituent materials was observed, which was attributed to the type-II band alignment of ZnO/ZnS MQWs. The type-II transition showed a significant blue shift with increasing excitation power, which originated from modified band bending caused by spatial separation of electrons and holes as electrons are confined in the ZnO conduction band quantum well and holes are confined in the ZnS valence band quantum well. The conduction band offset of the ZnO/ZnS heterojunction was determined to be 1.58 eV simulated from the type-II emission of the MQWs with controlled layer thicknesses. The type-II transition provides an important opportunity to utilize visible light emission and absorption for various optical and energy harvesting devices using the ZnO/ZnS material system.

    更新日期:2019-12-06
  • Extreme ultraviolet free-standing transmittance filters for high brilliance sources, based on Nb/Zr and Zr/Nb thin films on Si3N4 membranes: Design, fabrication, optical and structural characterization
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-05
    K. Jimenez, P. Nicolosi, L. Juschkin, Nadeem Ahmed, A.E.H. Gaballah, E. Cattaruzza, M.G. Sertsu, A. Gerardino, A. Giglia, G. Mussler, P. Zuppella

    Optical and structural properties of Niobium and Zirconium bilayer structures (Nb/Zr and Zr/Nb) were investigated in order to develop free-standing transmittance filters in the Extreme Ultraviolet region (EUV) between 5-20 nm. Samples of Nb/Zr and Zr/Nb were deposited on Silicon Nitride (Si3N4) membranes by magnetron sputtering technique, using metallic targets of Nb and Zr. A single layer of Zr and Nb on Si3N4 membrane has also been deposited and studied for a better understanding of the performance of these structures and their optical and mechanical properties. Optical microscope images of Zr and Zr/Nb structures on the membranes reveal compressive stress while Nb and Nb/Zr structures present tensile stress behavior. Nb and Nb/Zr self-standing filters were obtained by etching the silicon nitride membrane, with free-standing areas up to 3 × 3 mm2 with 100 nm of thickness. The transmittance performance of the samples has been measured by using EUV synchrotron radiation. The results show the highest peak transmittance of 60% at 7.02 nm and very good performance in the targeted range.

    更新日期:2019-12-05
  • Preparation and characterization of luminescent YPO4: Eu3+ thin films using sol gel spin coating method
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-05
    L. Benharrat, L. Guerbous, D. Bradai, A. Boukerika, A. Manseri, N. Selmi, B. Rahal, MSE. Hamroun

    Orange-red color emission obtained from YPO4: 5 at. % Eu3+ nanocrystalline thin films are prepared by spin coating sol gel route. The thorough study of two different sol gel routes and their effect on structural and luminescent properties of YPO4:Eu3+ are investigated. Prepared samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy and photoluminescence spectroscopy. This work demonstrated that the use of relatively stronger solvents during the sol gel route favorize the dissolution of oxide salts’ precursors within solutions and enhance their stabilization. XRD analysis indicated the formation of nanopowders and nanocrystalline thin films. Structural properties showed a strong correlation between the parameters related to samples’ solution and form. All samples showed uniform morphology with different sizes and shapes of particles depending on the solution and the form of the nanophosphor. Under UV excitation, YPO4: Eu3+ powders and thin films exhibited, orange-red color emissions assigned to 5D0 → 7FJ (J = 1, 2, 3 and 4) intraconfigurational transitions. Asymmetry ratio (R/O) analysis showed that Eu3+ in YPO4 host matrix tends to occupy high symmetry sites when prepared as thin films compared to powders. The thin film with better crystallinity and bigger particle sizes exhibited better emission efficiency but low symmetry of crystal field near Eu3+ ions (high R/O) and low light extraction ratio.

    更新日期:2019-12-05
  • Enhanced transparency of ultrathin Ag films using a wetting layer of phosphomolybdic acid
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-04
    Maciej Chrzanowski, Maksymilian Kliczkowski, Piotr Bieganski, Ewa Placzek-Popko, Jan Misiewicz, Artur Podhorodecki

    Phosphomolybdic acid (PMA) was exploited as a cost-efficient material in combined spin-coating/sputtering deposition of PMA/Ag transparent conductive electrode for optoelectronic applications. Sputtering of Ag on glass results in the grainy films which are characterized by low transmittance and poor conductivity. It is demonstrated that the wetting layer composed of spin-coated PMA provides perfect conditions for the formation of ultrathin (7–10 nm) and smooth (root-mean-square < 3 nm) Ag films. By optimizing the thickness of Ag film, the sheet resistance of 17 Ω/sq and the transmittance of 79% at 550 nm is achieved. Further improvement of electrode performance is shown for PMA/Ag/PMA multilayer where the top PMA is applied as a bifunctional layer to boost the transmittance up to 84% and to effectively encapsulate Ag film providing its long-term stability in ambient conditions.

    更新日期:2019-12-04
  • Microstructure of GaAs thin films grown on glass using Ge seed layers fabricated by aluminium induced crystallization
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-04
    D. Pelati, G. Patriarche, L. Largeau, O. Mauguin, L. Travers, F. Brisset, F. Glas, F. Oehler

    We perform the growth of GaAs epilayers by molecular beam epitaxy (MBE) on Ge pseudo-substrates obtained by the aluminium induced crystallisation (AIC) of thin amorphous Ge layers deposited on silica. Despite the apparent uniformity of the AIC-Ge layer, large domains (more than 50 μm wide) previously thought to be monocrystalline are found to actually consist in smaller grains (500 to 1000 nm wide), separated by low angle grain boundaries. These defects are transferred during epitaxy to the GaAs layer and degrade the quality of the III-V material. In our growth conditions, the MBE results in the selective deposition of thin GaAs layers on Ge with respect to the silica support, but selectivity is progressively lost with increasing layer thickness.

    更新日期:2019-12-04
  • Comparison of the properties of a-C:H films deposited from methane and heptane precursors: study of the mechanical, chemical and structural properties
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-03
    W.E.S.S. Viana, A. Elzubair, M.M. Wysard, D.F. Franceschini, S.S. Camargo

    In this work, thin films of hydrogenated amorphous carbon (a-C:H) were deposited on silicon substrates from heptane and methane precursors by the radio frequency plasma-enhanced chemical vapor deposition (PECVD) technique, varying the self-bias voltage from -100 V to -900 V. As a liquid, heptane is safer, easier to handle, to store and stock, and presented advantages over methane as a precursor in the deposition of a-C:H films by PECVD as it allows deposition rates more than 4 times higher than of methane. Diamond-like carbon films deposited from heptane were also harder (22.5 GPa) and presented smaller intrinsic stress (3.5 GPa) than those obtained from methane (18.8 GPa and 4.1 GPa, respectively). In addition, these films have a smaller hydrogen content and a reduced sp2 character. The observed behavior is consistent with the subplantation model, caused by the ion bombardment energy during deposition. The differences observed in the deposition from both precursors are related to the different number of carbon atoms of the parent molecules and lead to a change of structure and hardness that could be closely related to the structural changes observed by Raman spectroscopy. Films deposited from heptane may be promising for applications due to a higher hardness to elastic modulus ratio H/E of approximately 0.13 when compared to films deposited from methane.

    更新日期:2019-12-04
  • Multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-03
    N.F. Cunha, A. AL-Rjoub, L. Rebouta, L.G. Vieira, S. Lanceros-Mendez

    A multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering is presented. The design was first theoretically optimized using the optical constants, refractive index and extinction coefficient, of thin single layers. The spectral optical constants in the wavelength range from 0.3 to 27 µm were calculated from the transmittance and reflectance data of thin single layers deposited on silicon and glass substrates. The samples were characterized by Scanning Electron Microscopy, X-ray diffraction, Fourier-transform Infrared Spectroscopy and UV–VIS–NIR spectroscopy. It is shown that the TiO2 layer presents a partially rutile phase polycrystalline structure and a higher refractive index than amorphous SiO2 and SiNx layers in the spectral range from 0.3 to 2.5 μm. The cooling device was deposited on copper substrates and a thin low-density polyethylene foil with high transmittance in the 8 to 13 µm spectral range was used as convection cover material. The device is characterized by both low reflectance (high emittance) in the sky atmospheric window (wavelength range from 8 to 13 µm) and high hemispherical reflectance elsewhere, allowing for temperature drops of average 7.4°C at night-time in winter, which corresponds to a net cooling power of ∼43 W m−2. Further, a temperature drop of 2.5 °C was obtained during winter daytime.

    更新日期:2019-12-04
  • Fluorescence of Cr3+ ions in MgAl2O4 epitaxial nanosize spinel films on SrTiO3 substrates
    Thin Solid Films (IF 1.888) Pub Date : 2019-12-02
    S.P. Feofilov, A.B. Kulinkin, A.K. Kaveev, N.S. Sokolov, S.M. Suturin

    The fluorescence spectra of probe Cr3+ centers in MgAl2O4 spinel nanolayers of different thickness grown on SrTiO3 substrates were studied. The films were produced by laser molecular beam epitaxy. The fluorescence spectra strongly depend on nanofilm growth conditions. The Cr3+ ions 2E excited state lifetime was found to significantly differ from that in the bulk crystals. The role of Mg/Al inversion in the spinel lattice in the fluorescent properties is discussed.

    更新日期:2019-12-02
  • In-situ high temperature laser-induced damage of sol-gel Ta2O5 films with different dual additives
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-29
    Pu Zhang, Di Lin, Yongqiao Zhu, Wenzhe Cai, Dawei Li, Cheng Xu

    Using TaCl5 as the precursor, two types of Ta2O5 sols were synthesized with employment of different dual additives, namely, diethanolamine (DEA) with acetylacetone and DEA with polyethylene glycol (PEG). The prepared sol-gel Ta2O5 films were featured by the low surface roughness, high transmittance, low absorption and high laser-induced damage threshold (LIDT). The highest LIDT of 29.1 J/cm2 was obtained in the film prepared with the DEA and PEG additives. This should be attributed to the chelation effect of DEA and the steric hindrance imposed by PEG, which synergistically resulted in a more regular three-dimensional network structure and consequently lower film internal defects. In the case of temperature increase to 150°C, the LIDT levels of both the films decreased. The damage morphologies indicated the defect-induced mechanism for the films irradiated either at the room temperature, or at the high temperature of 150°C. Moreover, an evolution model was proposed to reveal the effect of dual additives on the structure of Ta2O5 films. This study was conducive to a better understanding of the fundamental laser damage mechanism and exploring the potential application of sol-gel films in high temperature environment.

    更新日期:2019-11-30
  • Sodium doping of Cu2O layers by reactive annealing of Cu2O covered with a NaCl nano-film in a low-oxygen atmosphere
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-27
    Laura Hill Pastor, Tomas Díaz Becerril, Miguel Galván Arellanob, Ramón Peña Sierra

    P-type conductivity enhancement of cuprous oxide Cu2O films covered with sodium chloride (NaCl) nano-layer using the reactive annealing method is reported in the present study. Effects of the NaCl nano-layer on the surface morphology, structural characteristics, and electrical properties of the material are discussed. Changes in the surface morphology and chemical composition of Cu2O films produced by the annealing process were studied by scanning electron microscopy and energy dispersive spectroscopy analysis, respectively. The structure of the Cu2O film was studied by x-ray diffraction analysis and Raman spectroscopy. The Raman results demonstrate the reduction of the cupric oxide CuO phase formed above the Cu2O layer by natural progressive oxidation. After performing the reactive annealing process, electrical resistivity decreased from 900 to 90 Ω cm due to the incorporation of sodium into the Cu2O lattice. An increase in carrier mobility was observed with respect to the as-grown Cu2O films, which may be attributed to the decrease in structural defects. A discussion on the stability of Cu2O in comparison to the CuO phase when copper oxide films are covered with a NaCl nano-layer is also provided.

    更新日期:2019-11-27
  • Low-temperature plasma annealing of sputtered indium tin oxide for transparent and conductive thin-films on glass and polymer substrates
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-25
    Eric Klein, Kilian Huber, Oliver Paul, Patrick Ruther

    This paper reports on the development of a low-temperature plasma annealing process for indium tin oxide (ITO) thin-films deposited by magnetron sputtering. The study investigates the influence of the type of plasma (argon (Ar) vs. oxygen (O2)) and its duration on the optical transmission coefficient and electrical resistivity of the films depending on the power and O2 concentration during their deposition. A low sputtering power of 100 W combined with an O2 concentration of 6 vol% followed by a 40-min Ar plasma anneal at 300 W produces ITO films with an average transmission of 94% in the visible spectrum and a resistivity of 2.3×10−3 Ωcm. Sputtering without O2 results in a transmission of 89% and a resistivity of 9×10−4 Ωcm. The annealing depth is found to be 370 nm. We deposited and annealed conductive, transparent ITO tracks below 50 ∘C on a polyimide substrate and thereby operated integrated light sources on a fully transparent and highly flexible optical probe.

    更新日期:2019-11-26
  • Effects of Pulse Power and Argon Flux Flow Rate on Mechanical and Tribological Properties of Diamond-like Carbon Coatings Prepared Using High Power Impulse Magnetron Sputtering Technology
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-23
    W.H. Kao, Y.L. Su, J.H. Horng, C.C. Yu

    Diamond-like carbon (DLC) coatings were deposited on SKH51 disks using a high power impulse magnetron sputtering (HiPIMS) system. Preliminary experiments were performed to determine the HiPIMS conditions which maximized the DLC coating hardness. The composition, structure, mechanical and tribological properties of the DLC coatings were then systematically explored for different values of the HiPIMS pulse power and argon flux flow rate. For given values of the HiPIMS deposition time, pulse current and deposition distance, a high DLC coating nanohardness (19.77 GPa) was obtained using a pulse power of 5 kW and an argon flux flow rate of 100 sccm. However, the coating exhibited the lowest adhesive strength (i.e., a critical load (Lc) of just 6 N). By contrast, the coating prepared with a pulse power of 5 kW and an argon flux flow rate of 80 sccm had the highest nanohardness (22.88 GPa) and a greatly improved adhesive performance (Lc=73 N). However, it showed the lowest wear rate among all of the coatings when sliding against an Al2O3 ball under loads of 6 ∼ 14 N. The coating deposited with a pulse power of 4 kW and an argon flux flow rate of 100 sccm possessed the highest critical load of all the coatings (Lc=94 N), and thus exhibited the longest wear life when sliding against the Al2O3 ball (∼129,756 cycles). When sliding against an AISI 52100 ball, all of the coatings showed an excellent tribological performance, including a low wear rate and a long wear life (more than 150,000 cycles).

    更新日期:2019-11-26
  • Optimized hydrogen concentration within a remotely induced hollow-anode plasma for fast chemical-vapor-deposition of photosensitive and preferential microcrystalline silicon thin-films
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-23
    Toshihiro Tabuchi, Yasumasa Toyoshima, Shinichi Fujimoto, Masayuki Takashiri

    The chemical-vapor-deposition of photosensitive hydrogenated-microcrystalline-silicon (µc-Si:H) thin films with <110>-preferential orientation was optimized by altering the concentration of hydrogen within a high-density hollow-anode plasma. The µc-Si:H thin films were grown using a ratio of hydrogen (H2) to monosilane (SiH4) in the range of 1.25 ≤ [H2]/[SiH4] ≤ 35, with a gas pressure of 80 Pa. The high-density hollow-anode plasma was excited remotely in a processing space by transferring a hollow-cathode plasma via a nozzle on a partition plate, which separated the processing space from a hollow-cathode discharge space and served as an anode in an ultra-high vacuum hollow-electrode-enhanced glow-plasma transportation (HEEPT) system. The hollow-cathode plasma was excited by applying very-high-frequency (VHF, 105 MHz) power to a cathode in the hollow-cathode discharge space. The growth rate, crystalline volume fraction, and <110>-preferential crystal orientation of the films exhibited almost linear correlations with the ratio of the optical emission intensities of hydrogen atoms (Hα: 656 nm) and monosilane radicals (SiH*: 414 nm) (i.e. HαI/SiH*I). Reducing the [H2]/[SiH4] ratio by decreasing [H2] improved the growth rate, crystalline volume fraction, and <110>-preferential crystal orientation of the films. These results indicated that lower concentration of H2 was optimal for the fast deposition of photosensitive µc-Si:H thin-films with <110>-preferential crystal orientation using the HEEPT system. The <110>-preferential crystal orientation was less dependent on the VHF power, whereas the growth rate and crystalline volume fraction increased as the VHF power was increased. This result suggested that there would be a room for faster growth with retaining <110>-preferential crystal orientation.

    更新日期:2019-11-26
  • Microstructural and optical properties investigation of variable thickness of Tin Telluride thin films
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-21
    Praveen Tanwar, Amrish K. Panwar, Sukhvir Singh, A.K. Srivatava

    A series of Tin Telluride (SnTe) thin films of varied thicknesses are deposited on glass substrates at room temperature using thermal evaporation technique. The optical and microstructural properties of SnTe thin films of thicknesses 33 nm to 275 nm are reported. High-resolution x-ray diffraction patterns of SnTe thin films revealed the polycrystalline nature with [200] orientation having cubic structure. The microstructural and morphological structures of these films were examined using high-resolution transmission electron microscopy and scanning electron microscopy, respectively. The distribution of isotopes of various elements in the thin film along with lateral and longitudinal directions was determined by depth profile measurement using the time of flight - secondary ion mass spectroscopy technique. Fourier transform infrared spectroscopy spectra reveal the molecular vibrations, narrow bandgap property of material and suitability of materials in infrared applications. Longitudinal – optical phonon scattering due to the [222] orientation was observed in the micro-Raman spectra at room temperature which corresponds to a peak in the range 120–130 Raman shift/cm−1. Hence, the change in optical and microstructural properties at the nano-regime resulted in a shift towards the near-infrared region with an increase in the thickness of the thin films.

    更新日期:2019-11-21
  • Nano-patterned honeycomb structure of monolayer copper selenide on Cu(111)
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-21
    Qinmin Guo, Yu Zhong, Min Huang, Shuangzan Lu, Yinghui Yu

    Transition metal dichalcogenides generally have three atomic layers forming a buckled honeycomb structure as a covalent sheet. The van der Waals force is the key interaction between these sheets. In our work, we have fabricated a single layered copper selenide structure by employing molecular beam epitaxy method. The selenium and copper atoms form a Moiré pattern with respect to the substrate Cu(111). Combined with density functional theory calculation, the narrow band gap of these structures is investigated in detail.

    更新日期:2019-11-21
  • Effect of hydrazine hydrate as complexing agent in the synthesis of zinc selenide thin films by chemical bath deposition
    Thin Solid Films (IF 1.888) Pub Date : 2019-11-20
    D.D. Hile, H.C. Swart, S.V. Motloung, T.E. Motaung, K.O. Egbo, L.F. Koao

    ZnSe thin films were deposited using hydrazine hydrate (HH) as the only complexing agent. The deposition was carried out on glass substrates in an alkaline medium at low temperature using the chemical bath deposition method. The films were annealed at 300 °C for 2 h. The effects of varying the HH volumes on the structural and optical properties of the films were investigated. The investigations were based on glancing incidence X-ray diffraction, Raman spectroscopy, Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy (EDS), UV-Visible spectrophotometry, and photoluminescence (PL) spectroscopy. The results revealed that the ZnSe films were of the wurzite structure. Raman spectra showed longitudinal optical vibrational peaks with intense peak at around 251 cm−1. There were fluctuations in the Raman peaks intensities. However, the intensity of the 20 mL HH sample emerged the highest. The morphology of the thin films changed from spherical grains to nanoflakes as the HH volume was increased from 5 to 35 mL, respectively. EDS of the films confirmed the presence of Zn and Se. The bandgaps of the films decreased with an increase in the HH volume. PL measurements indicated two emission peaks at 530 and 678 nm when excited at 325 nm. These emission peaks are attributed to the intrinsic intra-bandgap defects. The intensities of the peaks increased with an increase in the HH volume. The commission Internationale de l'Elcairage color coordinates confirmed that the deposited ZnSe films exhibited green-red emission and the emission color was influenced by varying the HH volumes.

    更新日期:2019-11-20
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