Characterization of electrodeposited Bi2S3 thin films by holographic interferometry

Optical non destructive evaluation methods, using lasers as the object illumination source, include holographic interferometry. It is widely used to measure stress, strain, and vibration in engineering structures. Double exposure holographic interferometry (DEHI) technique is used to determine thickness and stress of electrodeposited bismuth trisulphide (Bi₂S₃) thin films for various deposition times. The same is tested for other concentration of the precursors. It is observed that, increase in deposition time, increases thickness of thin film but decreases stress to the substrate. The structural, optical and surface wettability properties of the as deposited films have been studied using X-ray diffraction (XRD), optical absorption and contact angle measurement, respectively. The X-ray diffraction study reveals that the films are polycrystalline with orthorhombic crystal structure. Optical absorption study shows the presence of direct transition with band bap 1.78 eV. The water contact angle measurement shows hydrophobic nature of Bi₂S₃ thin film surface.     

Preparation of Bi2S3 thin films with a nanoleaf structure by electrodeposition method

Nanoleaf-like Bi₂S₃ thin films were deposited on indium tin oxide (ITO) glass using Bi(NO₃)₃ and Na₂S₂O₃ as precursors by a cathodic electrodeposition process. The as-deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and photoluminescence spectrum (PL). The influence of precursor solution mole concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] on the phase compositions, morphologies and photoluminescence properties of the obtained thin films were investigated. Results show that a uniform Bi₂S₃ thin film with nanoleaf structure can be obtained with the precursor solution concentration ratio [Bi(NO₃)₃]/[Na₂S₂O₃] = 1:7. The as-prepared thin films exhibit blue-green photoluminescence properties under ultraviolet light excitation. With the increase of concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] in the deposition solution, the crystallizations and PL properties of Bi₂S₃ thin films are obviously improved.     

Optimization of annealing conditions of In2S3 thin films deposited by vacuum thermal evaporation

In₂S₃ thin films were grown on glass substrates by means of the vacuum thermal evaporation technique and subsequently thermally annealed in nitrogen and free air atmosphere from 250 to 350 °C for different durations. Experimental parameters have been adjusted in order to optimize the annealing conditions, and to obtain high band gap energy at low deposition temperature, as required for photovoltaic applications. In order to improve our understanding of the influence of the deposition and annealing parameters on device performance, we have investigated our indium sulfide material by X-ray diffraction, energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM) and spectrophotometry. The optical and structural properties of the films were studied as a function of the annealing temperature and durations. X-ray diffraction analysis shows the initial amorphous nature of deposited In-S thin films and the phase transition into crystalline In₂S₃ upon thermal annealing. Films show a good homogeneity and optical direct band gap energy about 2.2 eV. An annealing temperature of 350 °C during 60 min in air atmosphere were the optimal conditions.     

Influence of [S2O3]/[Sm] on Sm2S3 thin films deposited by liquid phase deposition method on self-assembled monolayers

Sm₂S₃ thin films were prepared on Si (1 0 0) substrates using SmCl₃ and Na₂S₂O₃ as precursors by liquid phase deposition method on self-assembled monolayers. The influence of the molar concentration ratio of [S₂O₃²⁻]/[Sm³⁺] on the phase compositions, surface morphologies and optical properties of the as-deposited films were investigated. The as-deposited Sm₂S₃ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet-visible (UV-vis) and photoluminescence spectrum (PL). Results show that it is important to control the [S₂O₃²⁻]/[Sm³⁺] during the deposition process and monophase Sm₂S₃ thin films with orientation growth along (0 1 1) direction can be achieved when [S₂O₃²⁻]/[Sm³⁺] = 2.0, pH 3.0, with citric acid as a template agent. The as-deposited thin films exhibit a dense and crystalline surface morphology. Good transmittance in the visible spectrum and excellent absorbency of ultraviolet light of the thin films are observed, and the band gap of the thin films first decrease and then increase with the increase of the [S₂O₃²⁻]/[Sm³⁺]. The as-deposited thin films also exhibit red photoluminescence properties under visible light excitation. With the increase of the [S₂O₃²⁻]/[Sm³⁺] in the deposition solution, the PL properties of Sm₂S₃ thin films are obviously improved.     

光折变法制备的As2S8条形波导的光阻断效应

实验研究了As₂S₈薄膜光折变现象.提出并采用紫外光激励的方法试制了As₂S₈条形波导，导模激励显示该波导具有良好的导波特性.在此基础上，考察了As₂S₈条波导的光阻断效应，实现了光-光效应的开关功能. 关键词： 光波导技术 2S₈条形波导')" href="#">As₂S₈条形波导 光阻断效应 光激励法     

Chemical bath deposition of Bi2S3 films by a novel deposition system

Bismuth sulfide (Bi₂S₃) films were chemically deposited by a novel deposition system in which ammonium citrate was used as the chelating reagent. Two sulfur source thioacetamide (TA) and sodium thiosulfate (Na₂S₂O₃) were used to prepare Bi₂S₃ films. Both the as-prepared films have amorphous structure. However, annealing can improve the crystallization of the films. The composition of the films prepared by TA and Na₂S₂O₃ are all deviate from the stoichiometric ratio of Bi₂S₃. The Bi₂S₃ films are all homogeneous and well adhered to the substrate. The optical properties of the Bi₂S₃ films are studied. The electrical resistivity of the as-prepared films are all around 7 × 10³ Ω cm in dark, which decreases to around 1 × 10³ Ω cm under 100 mW/cm² tungsten-halogen illumination. After the annealing, the dark resistivity of the Bi₂S₃ film prepared by TA decreases by four magnitudes. In contrast, the dark resistivity of the Bi₂S₃ film prepared by Na₂S₂O₃ only decreases slightly.     

CuInS2 thin films obtained through the annealing of chemically deposited In2S3-CuS thin films

In this work, we report the formation of CuInS₂ thin films on glass substrates by heating chemically deposited multilayers of copper sulfide (CuS) and indium sulfide (In₂S₃) at 300 and 350 °C in nitrogen atmosphere at 10 Torr. CIS thin films were prepared by varying the CuS layer thickness in the multilayers with indium sulfide. The XRD analysis showed that the crystallographic structure of the CuInS₂ (JCPDS 27-0159) is present on the deposited films. From the optical analysis it was estimated the band gap value for the CIS film (1.49 eV). The electrical conductivity varies from 3 × 10⁻⁸ to 3 Ω⁻¹ cm⁻¹ depending on the thickness of the CuS film. CIS films showed p-type conductivity.     

A chemical lithography route to Bi2S3 nanotubes

Two different semiconducting bismuth sulfide (Bi₂S₃) nanostructures (feather-like Bi₂S₃ nanotubes and fiber-like Bi₂S₃ nanotubes) with diameters around 50-60 nm and lengths about tens of micrometers were prepared successfully by a chemical lithography route. The results indicated that the employment of polyvinylpyrrolidone led to the precursor with feather-like morphology and the acid had ripening effect on and etching action to the ultimate formation of the fiber-like Bi₂S₃ nanotubes. The photoluminescence spectra of two different Bi₂S₃ nanostructures revealed that the relative position of emission peaks was influenced by the thin edges of the feather-like nanotubes due to the quantum-confinement effect.     

Investigations on co-evaporated Cu2SnSe3 and Cu2SnSe3-ZnSe thin films

Cu₂SnSe₃ is an important precursor material for the growth of Cu₂ZnSnSe₄, an emerging solar cell absorber layer via solid state reaction of Cu₂SnSe₃ and ZnSe. In this study, we have grown Cu₂SnSe₃ (CTSe) and Cu₂SnSe₃-ZnSe (20%) films onto soda-lime glass substrates held at 573 K by co-evaporation technique. The effect of annealing of these films at 723 K for an hour in selenium atmosphere is also investigated. XRD studies of as-deposited Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films indicated SnSe as secondary phase which disappeared on annealing. The direct optical band gap of annealed Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films were found to be 0.90 eV and 0.94 eV respectively. Raman spectroscopy studies were used to understand the effect of ZnSe on the properties of Cu₂SnSe₃.     

Effects of the substrate temperature on the properties of CuIn5S8 thin films

Structural, optical and electrical properties of CuIn₅S₈ thin films grown by thermal evaporation have been studied relating the effects of substrate heating conditions of these properties. The CuIn₅S₈ thin films were carried out at substrate temperatures in the temperature range 100-300 °C. The effects of heated substrate on their physico-chemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), optical transmission and hot probe method. X-ray diffraction revealed that the films are strong preferred orientation along the (3 1 1) plane upon substrate temperature 200 °C and amorphous for the substrate temperatures below 200 °C. No secondary phases are observed for all the films. The composition is greatly affected by heated substrate. From the optical transmission and reflection, an important absorption coefficient exceeds 10⁵ cm⁻¹ at 800 nm was found. As increasing the substrate temperature, the optical energy band gap decreases from 1.70 eV for the unheated films to 1.25 eV for the deposited films at 300 °C. It was found that CuIn₅S₈ thin film is an n-type semiconductor at 250° C.     

Structural and optical properties of Er, Yb co-doped Y2O3 thin films

Thin Er³⁺, Yb³⁺ co-doped Y₂O₃ films were grown on (1 0 0) YAG substrates by pulsed laser deposition. Ceramic targets having different active ion concentration were used for ablation. The influence of the rare-earth content and oxygen pressure applied during the deposition on the structural, morphological and optical properties of the films were investigated. The films deposited at the lower pressure, 1 Pa, and at 1/10 Er to Yb doping ratio are highly textured along the (1 1 1) direction of the Y₂O₃ cubic phase. In addition to the crystalline structure, these films possess smoother surface compared to those prepared at the higher pressure, 10 Pa. All other films are polycrystalline, consisting of cubic and monoclinic phases of Y₂O₃. The rougher surface of the films produced at the higher-pressure leads to higher scattering losses and different behavior of the reflectivity spectra. Optical anisotropy in the films of less than 0.004 was measured regardless of the monoclinic structure obtained. Waveguide losses of about 1 dB/cm at 633 nm were obtained for the films produced at the lower oxygen pressure.     

Substrate effects on V2O3 thin films

We apply density functional theory and the augmented spherical wave method to analyze the electronic structure of V₂O₃ in the vicinity of an interface to Al₂O₃. The interface is modeled by a heterostructure setup of alternating vanadate and aluminate slabs. We focus on the possible modifications of the V₂O₃ electronic states in this geometry, induced by the presence of the aluminate layers. In particular, we find that the tendency of the V 3d states to localize is enhanced and may even cause a metal-insulator transition.     

机械合金化过程对硫化铋块体热电性能的影响机理

以机械合金化法(MA)结合放电等离子烧结技术(SPS)制备了Bi₂S₃多晶块体热电材料. 研究了MA过程中干磨转速、湿磨时间和湿磨介质对Bi₂S₃多晶热电材料电传输性能的影响. 分析了样品的物相, 观察了显微组织, 测试了电传输性能和热传输性能. 研究表明, 以无水乙醇为湿磨介质时, 随着湿磨时间的延长, 出现了微量Bi₂O₃第二相, 样品的晶粒尺寸减小, 电阻率大幅增加, 功率因子下降. 以丙酮为湿磨介质时, 虽然不存在微氧化反应, 但是由于样品中存在大量孔洞, 导致功率因子降低. 425 r/min 干磨15 h后未湿磨的样品在573 K取得最大的ZT值0.25, 是目前文献报道的最高值.     

VO2-WO3 nanocomposite thin films synthesized by pulsed laser deposition technique

Pure VO₂ and VO₂-WO₃ composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO₃ molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO₂-WO₃ nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO₂ phase (m-VO₂) up to 10% of WO₃ content whereas both m-VO₂ as well as h-WO₃ (hexagonal WO₃) phases were present at higher WO₃ content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO₃ content. Temperature dependence of resistivity (R-T) measurements indicates significant variation in metal-insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO₂-WO₃ thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO₃ in VO₂ is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.     

Hydroxyethyl cellulose-assisted hydrothermal synthesis of Bi2S3 urchin-like colonies

Orthorhombic Bi₂S₃ with different morphologies was successfully synthesized by the acid-catalyst hydrothermal reactions of bismuth nitrate (Bi(NO₃)₃) and thiourea (NH₂CSNH₂) solutions containing different amounts of hydroxyethyl cellulose (HEC). Phase, morphologies, and optical properties were characterized by X-ray diffraction, selected area electron diffraction, scanning and transmission electron microscopy, and ultraviolet-visible spectroscopy. The products, hydrothermally synthesized in the HEC-free, 0.25 g HEC-added, 0.5 g HEC-added and 1.00 g HEC-added solutions, were respectively proved to be orthorhombic Bi₂S₃ irregular nanorods, complete urchin-like colonies of regular nanorods, incomplete urchin-like colonies of regular nanorods, and highly crystalline regular nanorods growing along the [001] direction. Tauc band gaps of the orthorhombic Bi₂S₃ nanorods, synthesized in the HEC-free, 0.25 g HEC-added, and 1.00 g HEC-added solutions were determined to be 3.0, 1.75 and 1.8 eV, respectively. Formation mechanism of orthorhombic Bi₂S₃ nanorods, synthesized in the HEC-free and HEC-added solutions, was also discussed at great detail.     

Optical and electrical properties of Y2O3 thin films prepared by ion beam assisted deposition

Y₂O₃ thin films were deposited by ion beam assisted deposition (IBAD) and the effects of fabrication parameters such as substrate temperature and ion energy on the structure, optical and electrical properties of the films were investigated. The results show that the deposited Y₂O₃ films had less optical absorption, larger refractive index, and better film crystallinity with the increase of substrate temperature or ion energy. The as-deposited Y₂O₃ films without ion-beam bombardment had larger relative dielectric constant (?_r) and the ?_r decreased with time even over by 40%, while the ?_r of films prepared with high ion energy had less changes, only less than 3%. Also, with the increase of ion energy, the electrical breakdown strength and the figure of merit increased.     

Cu2ZnSnSe4 thin films prepared by selenization of co-electroplated Cu-Zn-Sn precursors

A novel technique for growth of high quality Cu₂ZnSnSe₄ (CZTSe) thin films is reported in our work. The CZTSe thin films were fabricated onto Mo layers by co-electroplating Cu-Zn-Sn precursors followed by annealing in the selenium vapors at the substrate temperature of 550 °C. The morphology and structure of CZTSe thin films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum, respectively. The results revealed that the single phase was in the CZTSe thin films, and the other impurities such as ZnSe and Cu₂SnSe₃ were not existed though they were difficult to distinguish both from EDS and XRD.     

Numerical investigation on buffer performance based on acoustic excitation by stimulated Brillouin scattering in an As2Se3 fiber

Buffer performance of a 2.5 Gb/s bit stream with non-return-to-zero format is investigated based on acoustic excitation by stimulated Brillouin scattering in an As₂Se₃ fiber. The storage process and the retrieval process of the bit stream are separately controlled by a “Write” pulse and a “Read” pulse. The research results show that the output signal-to-noise ratio and the readout efficiency of the buffer are agreeable, and the pulse distortion is low, if both the “Write” and the “Read” pulses are with high enough peak power and spectrum wider than that of the signal pulse. Buffering of a consecutive 10-bit-long 2.5 Gb/s NRZ bit stream has also been demonstrated in the As₂Se₃ fiber with length of only 0.5 m. The storage of a long bit stream, such as the data packet containing about 1000 bits in the telecommunications, is limited by the high loss in the As₂Se₃ fiber. However, the development of the special optical fiber with high Brillouin gain coefficient, long acoustic lifetime and low loss can make this technology applicable for all-optical buffering in high speed optical networks.     

Structural, optical and electrical studies on pulse electrodeposited CdIn2S4 thin films

CdIn₂S₄ thin films were prepared by pulse electrodeposition technique over F:SnO₂ glass and stainless steel substrates in galvanostatic mode from an aqueous acidic bath containing CdSO₄, InCl₃ and Na₂S₂O₃. The growth kinetics of the film has been studied and the deposition parameters such as electrolyte bath concentration, bath temperature, time of deposition, deposition current and pH of the bath are optimized. X-ray diffraction (XRD) analysis of the as deposited and annealed films shows polycrystalline nature. Energy dispersive analysis by X-ray (EDAX) confirms nearly stoichiometric CdIn₂S₄ nature of the film. Scanning electron microscope (SEM) studies show that, the deposited films are well adherent and grains are uniformly distributed over the surface of the substrate. The optical transmission spectra show a direct band gap of 2.16 eV. Conductivity measurements have been carried out at different temperatures and electrical parameters such as activation energy, trapped energy state and barrier heights etc. have been determined.