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  • Enhanced Mechanical Quality Factor of 32 Mode Mn Doped 71Pb(Mg 1/3 Nb 2/3 )O 3 –29PbZrTiO 3 Piezoelectric Single Crystals
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-08
    Atul Thakre, Ajeet Kumar, Dae-Yong Jeong, Geon-Tae Hwang, Woon-Ha Yoon, Ho-Yong Lee, Jungho Ryu

    Abstract The solid solution of relaxor and lead titanate single crystals have been an excellent choice for electromechanical applications such as energy harvesters, SONARs, transducers, and biomedical equipment. The mechanical quality factor (Qm) plays a crucial role in such applications using high power resonance condition. In this work, 32 mode (011) oriented along thickness direction, Generation-III piezoelectric single crystals based on PMN-PZT [71Pb(Mg1/3Nb2/3)O3–29PbZrTiO3] have been grown by solid state single crystal growth method. The Mn doping concentration in the crystals were systematically controlled within the range of 0 to 1.0 mol.%. The piezoelectric properties noticeably varied with the Mn doping concentration when the content is over 0.1 mol.%. In order to obtain significant enhancement in Qm in PMN-PZT single crystals, especially, the Mn doping concentration should be higher than 0.7 mol.% (which offers highest figure of merit) for high power resonance applications. Graphic Abstract

    更新日期:2020-01-17
  • Analysis on Trap States in p -Metal-Oxide-Semiconductor Capacitors with Ultraviolet/Ozone-Treated GaN Interfaces Through Frequency-Dispersion Capacitance–Voltage Measurements
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-02
    Kwangeun Kim

    The trap states at ultraviolet/ozone (UV/O3)-treated Al2O3/GaN interfaces of p-type metal-oxide-semiconductor capacitors (pMOSCAPs) are analyzed through a frequency-dispersion capacitance–voltage (C–V) measurements. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy are applied to confirm a formation of ultrathin oxide layer (Ga2Ox) on GaN surface by the UV/O3 treatment. The trapped charge density and interface trap density improved from 7.30 × 1011 to 2.79 × 1011 cm−2 eV−1 averaged over the bandgap of GaN and from 1.28 × 1013 to 4.08 × 1012 cm−2 eV−1 near the conduction band edge of GaN, respectively, owing to the passivation of Ga2Ox layer at the Al2O3/GaN interfaces. Mechanism for the improved trap states in pMOSCAPs is identified based on the reduced defect states at both Al2O3/Ga2Ox and Ga2Ox/GaN interfaces.

    更新日期:2020-01-17
  • Microwave Characteristics Analysis of Typical Photosensitive Material InP Under Weak Light Irradiation Based on Quasi-Optical Resonator
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-02
    Yafeng Li, En Li, Chengyong Yu, Chong Gao, Gaofeng Guo, Yong Gao

    In this paper, the microwave characteristics of typical photosensitive material InP under different light irradiation are studied. The measurement sensor is a reflection-type hemispherical quasi-optical resonator with an operating frequency range from 20 to 40 GHz, an operating mode of TEM00q, and a quality factor of 18,000 or more. For the short-time irradiation experiment, the variation of InP microwave characteristics with the irradiation power of 20 mW, 60 mW, 100 mW, and 200 mW, is studied by frequency-domain and time-domain scanning methods, respectively. The measurement results indicate that the microwave characteristics of InP change significantly even under weak light irradiation. Taking 100 mW and 200 mW irradiation power as examples, the long-time irradiation experiment performed on InP lasting 1.5 min is carried out. The measurement result curves clearly show the influence of the thermal and non-thermal effects on the InP microwave characteristics at the instant of the monochrome light source opening and closing and during irradiation. Furthermore, the temperature distribution of InP during 200 mW irradiation is real-time imaged by a thermal infrared imager to verify the existence of thermal effect during irradiation. The measurement results are in good agreement with the theoretical analysis.

    更新日期:2020-01-17
  • Preparation of Highly (002) Oriented Ti Films on a Floating Si (100) Substrate by RF Magnetron Sputtering
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-16
    Ji Hye Kwon, Du Yun Kim, Kun-Su Kim, Nong-Moon Hwang

    Abstract The possibility of preparing highly (002) oriented Ti films on the Si (100) substrate was studied using RF sputtering. The deposition behavior was compared between floating and grounded substrates at room temperature. Highly (002) oriented Ti films could be successfully prepared on the floating Si (100) substrate, which was revealed by X-ray diffraction and high resolution transmission electron microscope. To understand the different deposition behavior between floating and grounded substrates, the incident energy of ions during RF sputtering was estimated from the substrate temperature measured by the K-type thermocouple. The incident energy on the floating substrate was lower by 20% than that on the grounded substrate. It was suggested that the lower incident energy on the floating substrate would be responsible for the deposition of highly (002) oriented Ti films at room temperature. Graphic Abstract

    更新日期:2020-01-17
  • Fabrication of Columnar NaNbO 3 -Based Particles Through Topochemical Microcrystal Conversion
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-25
    Liangliang Liu, Rui Lv, Zhuangzhuang Guo, Yongqiang Wang

    The columnar NaNbO3-based particles with a perovskite structure were successfully synthesized through topochemical microcrystal conversion. First, the precursor was fabricated by facile MSS in the Nb2O5–KCl system. A good dispersion and high aspect ratio were satisfied simultaneously with a small amount of SrCO3 and KSr2Nb5O15 (KSN) seed. Then, columnar NaNbO3-based particles, 10 μm in length and 1 μm in diameter, were obtained via the simple molten salt reaction from the precursor. The results of NaNbO3-based ceramics suggested that the as-synthesized NaNbO3-based particles had the good mechanical properties and homogeneous chemical composition.

    更新日期:2020-01-17
  • Increase in Current Density at Metal/GeO 2 /n-Ge Structure by Using Laminated Electrode
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-19
    Takahiro Tsukamoto, Shota Kurihara, Nobumitsu Hirose, Akifumi Kasamatsu, Toshiaki Matsui, Yoshiyuki Suda

    In a metal/n-Ge structure, Fermi level pinning tends to occur. The insertion of an oxide layer at the interface between electrodes and n-Ge can effectively reduce the Schottky barrier height. However, the attachment of metal and oxide can cause diffusion of oxygen to the metal due to Gibbs free energy, which degrades the contact characteristics. In this study, we investigated the effects of a laminated electrode on the current density at a metal/GeO2/n-Ge structure. Ni, Pt, Al, or Ti layers with thicknesses of 0.5–20 nm were formed, followed by a deposition of 200-nm-thick Al. The J–V curves of these samples showed that the current density of the Al/Ti/GeO2/n-Ge structure was the largest among them and was about 126 times larger than that of the Al/GeO2/n-Ge structure. We also found that the current density depended on the film thickness of Ti and was the highest at the film thickness of about 2.5 nm or less. To investigate the effect of the Ti interlayer on the current density, we obtained the depth profiles of X-ray photoelectron spectroscope spectra of the Al/Ti/GeO2/n-Ge and Al/GeO2/n-Ge structures. Analysis showed that the diffusion of the oxygen to Al was limited by the 20-nm-thick Ti, and the oxygen was diffused to Al when the film thickness of Ti was about 1 nm. These results demonstrate that laminated oxide structures such as AlOx/TiOx and TiOx/GeO2 can form on the sample with 1-nm-thick Ti, which increases the current density.

    更新日期:2020-01-17
  • First-Principles Study of Black Phosphorus as Anode Material for Rechargeable Potassium-Ion Batteries
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-10-16
    Weiwei Yang, Yunxiang Lu, Chengxi Zhao, Honglai Liu

    Abstract In two-dimensional materials, black phosphorus has shown excellent performance as electrode materials for lithium- and sodium-ion batteries, due to its thermodynamic stability, layered anisotropic structure, and electrical conductivity. Recently, high capacity anodes based on black phosphorus as an active component for potassium-ion batteries (PIBs) have also been reported. However, in-depth studies are required to clarify the adsorption and diffusion of K ions on black phosphorus and the K–P reaction mechanism. In this work, the surface adsorption, bulk diffusion, and K–P binary phase formation were firstly investigated in detail using first-principle calculations. We found that compared with Li and Na, K has the lowest diffusion energy barrier in the bulk phase (0.182 eV for zigzag type and 2.013 eV for armchair type). Black phosphorus structure irreversibly collapses when the K ion concentration is up to 0.625, and no K3P phase is formed through the electrochemical profiles obtained by calculation of the binary phase alloy structures. Furthermore, the maximum capacitance of black phosphorous for PIBs is calculated to be 864.8 mAh.g−1. This work will help in understanding the mechanism and further improving the performance of K-ion batteries. Graphic Abstract

    更新日期:2020-01-17
  • Unveiling the Root Cause of the Efficiency-Lifetime Trade-Off in Blue Fluorescent Organic Light-Emitting Diodes
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-19
    Sunwoo Kang, Jun Yeob Lee, Taekyung Kim

    Abstract The origin of efficiency-lifetime trade-off in triplet–triplet fusion (TTF) type blue fluorescent organic light-emitting diodes (OLEDs) was investigated and the device structure to resolve the issue was developed. The efficiency and lifetime were simultaneously improved in the blue OLEDs by developing a multilayer hole transport stack which can adjust carrier densities and recombination zone in the emitting layer (EML). It was found that electron leakage from EML and high spatial density of excitons in the vicinity of the electron blocking layer for high TTF rates by narrow recombination zone are the detrimental factors for efficiency-lifetime trade-off. A multilayer hole transport stack employing a deep highest occupied molecular orbital hole transport layer and an electron blocking layer combined with an appropriate hole blocking layer simultaneously improved the power efficiency by 16% at 500 cd/m2 and lifetime by almost 100% (from 73 h up to 145 h). In addition, the low efficiency in the low luminance region was also completely controlled, resulting in negligible efficiency variation in the entire luminance range. Graphic Abstract

    更新日期:2020-01-17
  • Interfacial Perpendicular Magnetic Anisotropy in Magnetic Tunnel Junctions Comprising CoFeB with FeNiSiB Layers
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-20
    Do Kyun Kim, Minhyeok Lee, Junghoon Joo, Young Keun Kim

    Abstract Controlling ferromagnetic thickness (t) and properties such as saturation magnetization (Ms) and effective magnetic anisotropy constant (Keff) has been regarded as critical for the performance of magnetic tunnel junctions (MTJs) with interfacial perpendicular magnetic anisotropy. Here, we report the effects of hybridizing a CoFeB layer with a FeNiSiB layer as part of a magnetic free layer structure. We deposited thin film stacks by magnetron sputtering on Si wafers with thermal oxides and carried out post-deposition heat treatment at 300 °C for 1 h in a vacuum under a magnetic field. We found that Ms and Keff could be tuned by adding a layer of amorphous FeNiSiB. While the Ms and Keff values were modified, the tunneling magnetoresistance (TMR) ratios of the MTJs were maintained, even though the CoFeB thickness was decreased by half. Moreover, an asymmetric bias voltage dependence of TMR was suppressed in the MTJs with FeNiSiB/CoFeB hybrid free layers due to improvements in the interface quality between the CoFeB/MgO interfaces. Graphic Abstract

    更新日期:2020-01-17
  • Energy Storage Properties of Blended Polymer Films with Normal Ferroelectric P(VDF-HFP) and Relaxor Ferroelectric P(VDF-TrFE-CFE)
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-23
    Han-Bo Jung, Jin-Woo Kim, Ji-Ho Lim, Do-Kyun Kwon, Doo Hyun Choi, Dae-Yong Jeong

    With the recent development of wearable/portable electronic devices, the power sources need to be flexible and miniaturized. As the power supply, a dielectric capacitor is used for systems requiring high power in a short time, which in turn necessitates dielectric materials with high energy density and fast discharging time for device miniaturization. In this study, we attempt to improve the energy density of organic materials by blending normal ferroelectric P(VDF-HFP), which offers high dielectric breakdown strength, and relaxor ferroelectric P(VDF-TrFE-CFE), which provides a high dielectric constant. The role of P(VDF-HFP) as a defect in the P(VDF-TrFE-CFE) crystallite improved the properties of the relaxor-ferroelectrics. Increasing the terpolymer content in the blended films reduced the normal ferroelectric β-phase, which revealed that non-polar phase was induced. The copolymer and terpolymer were blended in various weight ratios (10:0, 7:3, 5:5, 3:7, 1:9 and 0:10) and cast into films. The blends with a copolymer/terpolymer ratio of 1:9 showed reduced hysteresis and remnant polarization, compared to those of the pure terpolymer, and a higher maximum polarization (Pmax) value at an electric field of 250 MV/m, indicating a less saturated polarization at high electric field. To conclude, the PVDF-based copolymer/terpolymer (1:9 ratio) blends showed the highest energy density (6.58 J/cm3).

    更新日期:2020-01-17
  • Effects of Low-Temperature GeSn Buffer Layers on Sn Surface Segregation During GeSn Epitaxial Growth
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-14
    Takahiro Tsukamoto, Nobumitsu Hirose, Akifumi Kasamatsu, Toshiaki Matsui, Yoshiyuki Suda

    We investigate the effects of the low-temperature (LT) GeSn buffer layers on Sn surface segregation during the growth of the additional GeSn layers. Sn surface segregation was observed in the GeSn layers formed on Si substrates at the growth temperature of 300 °C. However, there was no Sn surface segregation in the GeSn layers grown at 300 °C on the LT GeSn buffer layers formed at 225 °C. The Sn surface segregation was limited by the effects of the LT buffer layers. Crystallinity of the GeSn layers grown at 300 °C on the LT GeSn buffer layers was investigated by Raman spectroscopy. The full width at half maximum of the Ge–Ge Raman spectrum obtained from the GeSn layers was about 3.1 cm−1, which means that the formed GeSn layers have excellent crystallinity. We have successfully demonstrated that the LT GeSn buffer layers can limit the Sn surface segregation, which increases the growth temperature and improves crystallinity of the GeSn layers.

    更新日期:2020-01-17
  • Ultra-Low Voltage Metal Oxide Thin Film Transistor by Low-Temperature Annealed Solution Processed LiAlO 2 Gate Dielectric
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-23
    Anand Sharma, Nitesh K. Chourasia, Vishwas Acharya, Nila Pal, Sajal Biring, Shun-Wei Liu, Bhola N. Pal

    Low surface-roughness and high-capacitance ion-conducting LiAlO2 gate dielectric thin film has been fabricated by sol–gel technique to develop ultra-low voltage (≤ 1.0 V) indium-zinc-oxide thin film transistor (TFT). This LiAlO2 dielectric shows α-LiAlO2 and γ-LiAlO2 phases those have been fabricated at two different temperatures. For both phases, mobile Li-ion is responsible to achieve a high dielectric constant (κ) of the material that helps to reduce the operating voltage of TFT. Additionally, lower surface roughness of LiAlO2 thin film creates a low-density trap state in the semiconductor/dielectric interface which is capable to reduce operating voltage within 1.0-volt. The device with 700 °C annealed γ-LiAlO2 gate dielectric shows the best device performance with an electron mobility of 25 cm2 V−1 s−1 and an on/off ratio of 3 × 105. Instead, 350 °C annealed α-LiAlO2 dielectric require only one volt to saturate the drain current and shows its mobility and on/off ratio are 13.5 cm2 V−1 s−1 and 1 × 104 respectively. Such kind of unusually low operation voltage TFT fabrication becomes possible because of the higher Li+ mobility of α-LiAlO2 gate dielectric and very low surface trap density. A model on carrier transport mechanism has been prepossessed to explain this achievement.

    更新日期:2020-01-17
  • Back-Channel-Etched InGaZnO Thin-Film Transistors with Au Nanoparticles on the Back Channel Surface
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-07
    Peng Xiao, Wenfeng Wang, Yingyi Ye, Ting Dong, Shengjin Yuan, Jiaxing Deng, Li Zhang, Jianwen Chen, Jian Yuan

    Abstract In t for equipment. Graphic Abstract

    更新日期:2020-01-15
  • Plasma-Assisted Synthesis of Bicrystalline ZnS Nanobelts with Enhanced Photocatalytic Ability
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-13
    Qiushi Wang, Junhong Li, Wei Zhang, Min Zhong

    ZnS nanobelts have been synthesized by a reaction of Zn and S powders using the simple arc discharge method. The products were characterized using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, as well as energy-dispersive X-ray spectrometer. The results reveal that the ZnS nanobelts exhibit bicrystalline nanostructure. The roles of ion bombardment and plasma species in the growth of bicrystalline ZnS nanobelts are discussed. The ZnS nanobelts exhibit strong emission peaked at 516 nm under a 373 nm UV light excitation and excellent photocatalytic ability for degradation of methylene blue. This work represents a new strategy to synthesize bicrystalline nanostructures for design of optoelectronic nanodevices and photocatalysts.

    更新日期:2020-01-13
  • Giant Self-biased Magnetoelectric Effect in Pre-biased Magnetostrictive–Piezoelectric Laminate Composites
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-12-17
    Yong-Woo Lee, Bipul Deka, Il-Ryeol Yoo, Do-Woo Gwak, Jiung Cho, Hyun-Cheol Song, Jong-Jin Choi, Byung-Dong Hahn, Cheol-Woo Ahn, Kyung-Hoon Cho

    Abstract In this study, it is demonstrated that the giant self-biased magnetoelectric (SME) response can be achieved from a center-clamped magnetostrictive–piezoelectric laminate composite by employing magnetic tip masses. An asymmetric laminate structure consisting of two different magnetostrictive layers (Metglas and nickel) with opposite signs of piezomagnetic coefficient is introduced to promote structural bending resonance, and the effect of layout change of attaching the magnetic tip masses on SME responses is systematically investigated. The highest SME effect is observed when all magnetic tip masses are loaded on the Metglas layer and their magnetization directions are normal to the Metglas surface. It is proposed that not only the parallel magnetic domains to external magnetic field but also the non-parallel magnetic domains effectively contribute to the total magnetostriction. The fabricated SME laminates exhibit giant SME voltage coefficients ranging from 14.11 to 52.35 V cm−1 Oe−1, depending on the direction of the fields of the tip magnets. These high SME voltage output values and their controllability are promising for precision field sensors, magnetic energy harvesters and field-tunable devices. Graphic Abstract

    更新日期:2020-01-11
  • Interlayer Material Design Reducing Transient Liquid Phase Bonding Time
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-12-03
    Sunghyun Sohn, Byungrok Moon, Junghoon Lee, Namhyun Kang, Younghoon Moon

    Abstract Power semiconductors require a large bonding area for die attachment. For this purpose, transient liquid phase bonding (TLPB) was applied using fabricated interlayers, namely Sn–3Cu and Sn–10Cu, to study the intermetallic compound (IMC) formation, and the results were compared with those obtained with a pure-Sn interlayer. The Sn–3Cu and Sn–10Cu interlayers exhibited primary IMC fraction of 0.06 and 0.24, respectively, before the TLPB. For a Cu/interlayer/Cu sandwich structure, the TLPB was applied at 250 °C over various time periods (1–4 h). A reduction in the bonding time was more significant for a Sn–10Cu interlayer with a larger amount of primary IMCs than for the Sn–3Cu interlayer. The time exponent of the IMC fraction with respect to the bonding time was approximately 0.3 for all interlayers. This implies that the IMC growth mechanism is governed by a liquid channel or wet grain boundary diffusion. The nearly constant fraction and increasing size of the primary IMCs produced during the TLPB indicate that the primary IMCs coalesced during this process. The primary IMCs preferentially coalesced with the interface IMCs produced during the TLPB when they had the same crystalline orientation. Graphic Abstract

    更新日期:2020-01-06
  • Preparation of Fe–Co–P–Gr/NF Coating via Electroless Composite Plating as Efficient Electrocatalysts for Overall Water Splitting
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-02
    Kaihang Wang, Kaili Sun, Zihan Li, Zunhang Lv, Tianpeng Yu, Xin Liu, Guixue Wang, Guangwen Xie, Luhua Jiang

    The development of electrocatalysts with high activity and low Tafel slope for overall water splitting has become a crucial challenge to exploit the sustainable energy. Herein, we construct a Fe–Co–P–Gr catalyst on nickel foam (NF) support through electroless composite plating to realize the co-deposition of Fe–Co–P alloys and graphene quantum dots. Interestingly, graphene quantum dots exhibit obvious effects on electron mobility and active sites of Fe–Co–P–Gr/NF catalyst. In oxygen evolution reaction, the Fe–Co–P–Gr/NF catalyst exhibits a small overpotential of 230 mV at 10 mA cm−2 and fast kinetics with Tafel slope of 37.8 mV dec−1. Meanwhile, the Fe–Co–P–Gr/NF also has a superior hydrogen evolution reaction performance in 1.0 M KOH. Compared with the Fe–Co–P alloys, the Fe–Co–P–Gr/NF both as the anode and cathode require only 1.58 V to reach a current density of 10 mA cm−2. The successful preparation of Fe–Co–P–Gr/NF electrode through electroless composite deposition provides a new path to manufacture electrocatalysts for overall water splitting.

    更新日期:2020-01-04
  • Optimization of Transistor Characteristics and Charge Transport in Solution Processed ZnO Thin Films Grown from Zinc Neodecanoate
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-10-09
    Nikhil Tiwale, Satyaprasad P. Senanayak, Juan Rubio-Lara, Yury Alaverdyan, Mark E. Welland

    Solution processing of metal oxide-based semiconductors is an attractive route for low-cost fabrication of thin films devices. ZnO thin films were synthesized from one-step spin coating-pyrolysis technique using zinc neodecanoate precursor. X-ray diffraction (XRD), UV–visible optical transmission spectrometry and photoluminescence spectroscopy suggested conversion to polycrystalline ZnO phase for decomposition temperatures higher than 400 °C. A 15 % precursor concentration was found to produce optimal TFT performance on annealing at 500 °C, due to generation of sufficient charge percolation pathways. The device performance was found to improve upon increasing the annealing temperature and the optimal saturation mobility of 0.1 cm2 V−1 s−1 with ION/IOFF ratio ~ 107 was achieved at 700 °C annealing temperature. The analysis of experimental results based on theoretical models to understand charge transport envisaged that the grain boundary depletion region is major source of deep level traps and their effective removal at increased annealing temperature leads to evolution of transistor performance.

    更新日期:2020-01-02
  • Intercorrelated Relationship Between the Thermoelectric Performance and Mechanical Reliability of Mg 2 Si-Reduced Graphene Oxide Nanocomposites
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2020-01-01
    Gwansik Kim, Wonkyung Kim, Wooyoung Lee

    Abstract We fabricated Mg2Si-based thermoelectric nanocomposites with reduced graphene oxide using ultrasonic-based wet chemical pulverizing-mixing and spark plasma sintering to improve the trade-off relationship between thermoelectric properties and mechanical reliability. The dependence of thermoelectric properties and mechanical reliability on the nanophase morphologies has been systemically investigated, demonstrating the fracture toughness of the nanocomposite with thin reduced graphene oxide significantly increased. Moreover, the introduction of the few-layered reduced graphene oxide with high interface density was more effective in improving the trade-off relationship. This result suggests that an in-depth research on the dependence of the thermoelectric properties and mechanical reliability on the intrinsic properties of the nanophases is required to prepare efficient thermoelectric nanocomposites. Graphic Abstract

    更新日期:2020-01-01
  • Effect of Sn-Decorated MWCNTs on the Mechanical Reliability of Sn–58Bi Solder
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-09-25
    Choong-Jae Lee, Kyung Deuk Min, Hyun Joon Park, Jae-Ha Kim, Seung-Boo Jung

    Abstract The mechanical reliability of Sn–MWCNT composite solder containing various content of Sn-decorated MWCNTs (0, 0.05, 0.1, and 0.2 wt%) and Sn–58Bi solder were investigated. The Sn-decorated MWCNTs nanoparticles were used to improve the mechanical reliability of Sn–58Bi solder, which is a representative, low-temperature, lead-free solder. The Sn-decorated MWCNT nanoparticles were synthesized using the polyol method, and the Sn–MWCNT composite solder paste was fabricated by mechanical mixing. The shear and bending tests were conducted to evaluate the mechanical properties of the solder joints. We identified the microstructure of solder to investigate the intermetallic compound and failure mechanism of Sn–MWCNT composite solder. Furthermore, a high-temperature storage test at 100 °C for 1000 h was performed to determine long-term reliability. The shear strength and fracture energy increased about 21% and 23%, respectively, with 0.1 wt% Sn-decorated MWCNTs. In addition, the bending reliability of Sn–58Bi solder increased approximately 25%. Graphic Abstract

    更新日期:2020-01-01
  • Microstructural and Magnetic Characterization of Iron Oxide Nanoparticles Fabricated by Pulsed Wire Evaporation
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-08-16
    Young-Woo Kim, Hyun Soon Park

    Abstract The iron oxide nanoparticles (IONPs) fabricated by pulsed wire evaporation were characterized by analytical electron microscopy and magnetic properties measurement system (MPMS). The IONPs produced at various charging voltages (2.6, 5.0 and 6.3 kV) exhibited the average size of 48 nm and the differences in shape, i.e., spherical (83%) and hexagonal (17%) structures. The hexagonal nanoparticles showed single-crystalline magnetite (Fe3O4) with major facets made of {111} planes. The chemical shifts in core–shell nanoparticles were observed by electron energy loss spectroscopy, indicating a dependency of the edge position related to the oxidation state of Fe. From the MPMS, the saturation magnetization and the coercivity of IONPs were measured to be 64 emu/g and 37 Oe at 300 K, respectively. The results provide useful information for the relationship between the nanostructure and magnetic behavior. Graphic Abstract TEM images of iron oxide nanoparticles (IONPs) fabricated by pulsed wire evaporation. Two distinct shapes of IONPs can be seen, i.e., hexagonal and core/shell structures. The hexagonal nanoparticles showed single-crystalline Fe3O4 magnetite with major facets made of {111} planes, while the core/shell nanoparticle consisted of Fe core and Fe3O4 shell. By magnetic property measurement system (MPMS), the saturation magnetization and the coercivity were measured to be 64 emu/g and 37 Oe at 300 K, respectively. This study provides the possibility for developing novel and various IONPs with unprecedented structures and/or magnetic properties.

    更新日期:2019-12-31
  • A Novel Transparent Microwave Thin Film Coating Technique Applied to Dual-Band Antennas
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-10-01
    Yu-Ming Lin, Hung-Wei Wu, Yung-Wei Chen, Cheng-Yuan Hung, Shoou-Jinn Chang, Yan-Kuin Su

    In this paper, we propose a novel transparent microwave thin film coating technique and discuss its application in planar dual-band antennas (0.9/5.55 GHz). We developed a new process for activating the nano-alignment thin film from high to low resistivity (from 1.96 to 1.29 × 10−4 Ω cm) and from partial to full transparency (from 55 to 83% transmittance) within 150 s. The platform of the activation process comprises a periodic electrode, an optical microscope, and an alternating current signal generator. The periodic electrode can effectively rearrange the nano-alignment thin film into an ordered arrangement, which enhances the properties of the thin film in the microwave frequency range. A high-transparency and low-resistivity dual-band antenna is designed and fabricated using the proposed microwave thin film coating technique. The dual-band antenna has operating bandwidths of 740–960 and 5030–7030 MHz and potential applications in transparent electronics such as wearable devices and intelligent cars.

    更新日期:2019-12-17
  • Enhanced Ultra-violet Photodetection Based on a Heterojunction Consisted of ZnO Nanowires and Single-Layer Graphene on Silicon Substrate
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-28
    Yu Liu, Zengcai Song, Sheng Yuan, Lei Xu, Yanhui Xin, Meixia Duan, Shuxia Yao, Yangrui Yang, Zhenwei Xia

    In this study, heterojunction photoelectric devices based ZnO nanowires were fabricated on p-Si substrate with and without single-layer graphene as insert layer. ZnO nanowires and graphene were prepared by hydrothermal method and chemical vapor deposition respectively. The effect of insert layer on the morphology of ZnO nanowires was very weak as can be seen from scanning electron microscope and X-ray diffraction. Raman scattering showed that the graphene prepared was a single-layer structure. The ultraviolet detection performance of photodetectors with single graphene insert layer was much better than that of photodetectors without single graphene insert layer. The ultraviolet irradiation sensitivity of photodetectors with single graphene insert layer was up to 1071 which was improved 7 times than that of photodetectors without single graphene insert layer. Moreover, photodetectors with single graphene insert layer had faster response time (1.02 s) and recovery time (0.34 s).

    更新日期:2019-12-11
  • Comparison of Plasma Effect on Dewetting Kinetics of Sn Films Between Grounded and Floating Substrates
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-23
    Soon-won Park, Gil-su Jang, Kun-su Kim, Nong-moon Hwang

    When metal thin films deposited typically by sputtering is heated to sufficiently high temperature, thin films tend to disintegrate into individual isolated spherical particles, whose phenomenon is called thermal dewetting. If such metal films are exposed to plasma, however, the dewetting kinetics is enhanced dramatically. One possibility for enhanced dewetting kinetics is the ion bombardment on the film surface from plasma. The other possibility is the excess charge buildup on the film surface provided from plasma. If enhanced dewetting kinetics is due to charge buildup, it can provide an evidence for charge-enhanced kinetics, which has been suggested as a hypothesis to explain the evolution of void-free dense films in non-classical crystallization where the building block is charged nanoparticles. To clarify which is responsible for plasma enhanced dewetting, the dewetting behavior of 100 nm thick Sn films on silicon substrates with native oxide surface was compared between floating and grounded films in the inductively-coupled plasma environment. The dewetting kinetics on the floating film was much higher than that on the grounded film. These results indicate that the charge buildup is responsible for the plasma enhanced dewetting kinetics.

    更新日期:2019-12-11
  • Impact of Size on Humidity Sensing Property of Copper Oxide Nanoparticles
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-11-19
    Yang Gu, Huina Jiang, Zi Ye, Ning Sun, Xuliang Kuang, Weijing Liu, Gaofang Li, Xiaojun Song, Lei Zhang, Wei Bai, Xiaodong Tang

    Three sizes of CuO nanosheets were synthesized by hydrothermal method. The structure and morphology of CuO nanosheets were characterized by X-ray diffraction and scanning electron microscopy. Dielectrophoresis nano-manipulation technique was employed to arrange the materials on pre-designed Ti/Au electrodes to fabricate the three humidity sensors, and the sensing properties were then tested. The experimental results show that the sensitivity greatly increases with the decreasing size of CuO nanosheets, the sensitivity of sensor a, b, c are 369%, 3278%, 22,611% in 97.3% RH, respectively. The smaller sized CuO nanomaterials have better response characteristic, the response time of sensor a, b, c under 11.3–97.3% RH are 53 s, 49 s, 32 s, respectively. And correspondingly, hysteresis properties and the repeatability are also a little influenced. In addition, based on complex impedance spectroscopy and multilayer adsorption theory, the impact of size on humidity sensing property was discussed. The results indicated the feasibility to obtain higher performance of humidity sensor, especially the higher sensitivity, via employment the smaller size sensing nanomaterials.

    更新日期:2019-12-11
  • Correction to: Crystal Structure and XANES Study of Defect Perovskite (Y 1−x Pr x ) 1+δ Ba 2−δ Cu 3 O 7−y Compounds Prepared by Solid State Synthesis Method
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-08-24
    Poom Prayoonphokkharat, Penphitcha Amonpattaratkit, Anucha Watcharapasorn

    In the original publication of the article, the first author’s third affiliation is published incorrectly.

    更新日期:2019-12-11
  • Synthesis of Ag@rGO/g-C 3 N 4 Layered Structures and Their Application to Toxic Gas Sensors: Effect of Ag Nanoparticles
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-09-20
    Qui Thanh Hoai Ta, Gitae Namgung, Jin-Seo Noh

    In this work, graphitic carbon nitride (g-C3N4) was synthesized by simple pyrolysis of melamine, and it was hybridized with reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) using a stepwise solution method. AgNPs were randomly distributed on the surface of rGO/g-C3N4 layered hybrid structure, forming Ag@rGO/g-C3N4 composite. It was disclosed that the Ag@rGO/g-C3N4 composite responded to both oxidizing and reducing gases at room temperature, and its response was greatly enhanced from those of pristine rGO and rGO/g-C3N4. The room temperature responses of the composite were estimated at − 95% and 8% for 50 ppm of NO2 and NH3, respectively. The roles of structural components were discussed, and a gas-sensing mechanism was proposed based on the respective roles. In particular, AgNPs turned out to play an important role in the gas-sensing activity.

    更新日期:2019-12-11
  • S@GO as a High-Performance Cathode Material for Rechargeable Aluminum-Ion Batteries
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-09-17
    Kaiqiang Zhang, Tae Hyung Lee, Joo Hwan Cha, Ho Won Jang, Mohammadreza Shokouhimehr, Ji-Won Choi

    Aluminum-ion batteries (AIBs) are considered promising post lithium-ion batteries owing to their outstanding safety, gravimetric and volumetric capacities, and cost efficiency advantages. However, one practical obstacle to their development is the lack of reliable cathode materials that can be coupled with the distinguished Al anode. To address this issue, we synthesized a S@GO composite material for use as a cathode material in AIBs. The synthesized S@GO material exhibits a rod structure with a diameter of around 100 nm. Inside these nanorods, sulfur nanoparticles with a size of around 5 nm were uniformly anchored on the graphene sheets. By taking the advantage of an introduction of graphene sheets, the capacities were significantly preserved, displaying a capacity that was more than double that of a bare S active material. In addition, a 3000-cycle long-term repeated charge/discharge measurement exhibited extremely stable capacity values with a high Coulombic efficiency of 98% at the 3000th cycle. The charge/discharge processes were clearly shown during the repeated cycling measurement at a high current density of 1000 mA g−1. This work is expected to stimulate further study of elemental S used as a cathode material for high-performance AIBs.

    更新日期:2019-12-11
  • Properties of CoS 2 /CNT as a Cathode Material of Rechargeable Aluminum-Ion Batteries
    Electron. Mater. Lett. (IF 1.881) Pub Date : 2019-09-20
    Kaiqiang Zhang, Tae Hyung Lee, Joo Hwan Cha, Ho Won Jang, Mohammadreza Shokouhimehr, Ji-Won Choi

    Aluminum ion batteries (AIBs) are considered, in principle, promising post-lithium-ion batteries, which are potential for using in grid-scale energy storage and electric vehicles, owing to the economic Al. The inflammable ionic liquid electrolyte endows stable plating and stripping of Al ions. A spotlighted research on cathode material has been preforming to obtain a high-performance cathode material that can match well with the prominent Al foil. However, one over-looked factor for the study of cathode materials is the cost and possibility of mass-production. With this key point in mind, we as the forerunner studied the CoS2/carbon nanotubes (CNTs) composite cathode material composed of low cost and commercialized CoS2 and multi-wall CNTs to promote the development of AIBs. Stable charge/discharge plateaus (at 1.2/0.9 V vs. AlCl4−/Al) during cycling test were obtained for the CoS2/CNTs product at a high current density of 1000 mA g−1, with an extremely high Coulombic efficiency of 98% and reasonable electrochemical capacities. This report is expected to contribute more contribution in the development of cathode materials for rechargeable AIBs.

    更新日期:2019-12-11
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