The structure and properties of SnS thin films prepared by pulse electro-deposition

SnS films were prepared onto the ITO-coated glass substrates by pulse-form electro-deposition. The potential applied to the substrates was of pulse-form and its “on” potential, V_on was − 0.75 V (vs. SCE )and “off ” potential, V_off was varied in the range of − 0.1-0.5 V. The SnS films deposited at different V_off values were characterized by XRD, EDX, SEM and optical measurements. It shows that all the films are polycrystalline orthorhombic SnS with grain sizes of 21.54-26.93 nm and lattice dimensions of a = 0.4426-0.4431 nm, b = 1.1124-1.1134 nm and c = 0.3970-0.3973 nm, though the V_off has some influence on the surface morphology of the films and Sn/S ratio. When V_off = 0.1-0.3 V, the SnS films have the best uniformity, density and adhesion, and the Sn/S ratio is close to 1/1. The direct band gap of the films was estimated to be between 1.23 and 1.33 eV with standard deviation within ± 0.03 eV, which is close to the theoretical value. The SnS films exhibit p-type or n-type conductivity and their resistivity was measured to be 16.8-43.1 Ω cm.     

Effect of thickness on structural,optical, electrical and morphological properties of nanocrystalline CdSe thin films for optoelectronic applications

This paper presents effect of thickness on the physical properties of thermally evaporated cadmium selenide thin films. The films of thickness 445 nm, 631 nm and 810 nm were deposited employing thermal evaporation technique on glass and ITO coated glass substrates followed by thermal annealing in air atmosphere at temperature 300 °C. The as-deposited and annealed films were subjected to the XRD, UV–Vis spectrophotometer, source meter, SEM and EDS to find the structural, optical, electrical, morphological and compositional analysis respectively. The structural analysis shows that the films have cubic phase with preferred orientation (1 1 1) and nanocrystalline nature. The structural parameters like inter-planner spacing, lattice constant, grain size, number of crystallites per unit area, internal strain, dislocation density and texture coefficient are calculated. The optical band gap is found in the range 1.69–1.84 eV and observed to decrease with thickness. The electrical resistivity is found to increase with thickness for as-deposited films and decrease for annealed films. The morphological studies show that the as-deposited and annealed films are homogeneous, smooth, fully covered and free from crystal defects like pin holes and voids. The grains in the as-deposited films are densely packed, well defined and found to be increased with thickness.     

Sn膜硫化合成SnS薄膜及其性能研究

用热蒸发法技术在ITO透明导电玻璃上沉积一层Sn膜，将其装入石墨盒里后，放在真空炉里面硫化处理，硫化温度在150-350℃之间。通过对在不同温度下硫化的薄膜进行结构、成分和表面形貌分析，表明退火温度在230-250℃之间时所制得的薄膜为正交结构的SnS多晶薄膜，其均匀性和对基片的附着力都较好，具有（111）方向优先生长，薄膜粒径在200-800nm。通过测量薄膜样品的反射和透射光谱，计算得到其直接禁带宽度Eg=1．38eV，在基本吸收边附近的吸收系数大于10^4／cm，用霍尔测量系统测得其导电类型为P型，适合应用于太阳能电池的吸收层材料。     

Structural and optical properties of SnS nanoparticles and electron-beam-evaporated SnS thin films

SnS nanoparticles were synthesised by the precipitation method using SnCl₂.2H₂O and Na₂S.xH₂O and the nanoparticles were characterised by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. From the particles’ XRD pattern, a strong peak at 2θ = 31.5? was observed, which confirms the Herzenbergite orthorhombic crystal structure of SnS. The FTIR result also confirmed the SnS nanoparticles at 2354 cm^?1 and 615 cm^?1. Second, thin SnS films were prepared on a glass substrate by the electron beam evaporation technique at room temperature and annealed at 100°C, 200°C and 300°C. The effect of the annealing temperature on structural and optical properties of the SnS films was characterised by XRD and ultraviolet–visible (UV–Vis) analysis. From the experimental studies, optical absorption of SnS films increases with respect to the annealing temperature, while the values of band gap energy (E_g) get reduced from 1.77 to 1.57 eV.     

Structure and properties of SnS films prepared by electro-deposition in presence of EDTA

SnS thin films were deposited onto indium tin oxide (ITO) glass substrates by constant potential cathodic electro-deposition from aqueous solution containing stannous sulfate, ethylenediamine tetraacetate acid and sodium thiosulfate. The co-deposited potential was explored by cyclic voltammetry and the deposition potential (E) was roughly determined to be more negative than −0.70 V (vs. saturated calomel electrode, SCE). The analysis of the composition of the as-deposited films by X-ray fluorescence spectrometer indicated that stoichiometric SnS films could be obtained under the condition of E = −0.95 to −1.00 V. The films deposited at E = −1.00 V were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and their transmission and reflectance spectra were measured. The as-deposited films were polycrystalline SnS compound with orthorhombic crystalline structure and the ratio of Sn and S was nearly 1. The films were uniform and compact with small grains. The direct band gap of the films was estimated to be about 1.10–1.43 eV with an absorption coefficient near the fundamental absorption edge larger than 4 × 10⁴ cm⁻¹.     

真空热蒸发镀CIAS薄膜

采用真空热蒸发方法在普通玻璃基底上制备Cu In0.7Al0.3Se2(CIAS)薄膜,并对之进行450℃真空硒化退火处理。结果表明,制备的CIAS薄膜具有黄铜矿结构并且以(112)晶面优先生长。真空硒化退火后,薄膜晶体结构更完整,晶粒长大,成分分布均匀,更接近CIAS晶体的化学计量比。薄膜为P型半导体,退火后的薄膜禁带宽度减小至1.38 e V,带电粒子数下降至2.41E+17 cm-3,带电粒子迁移率增加至5.29 cm2/(N·s),电阻率升高至4.9Ω·cm。     

Optical properties of erbium oxide thin films deposited by electron beam evaporation

Erbium oxide thin films were deposited by electron beam evaporation on substrates heated to 300 °C. The effect of the introduction of oxygen on the structural, chemical and optical properties of the films was investigated. The films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy and normal-incidence transmittance and reflectance. The films had microcrystallites embedded in an amorphous matrix, and their stoichiometry was dependent on the oxygen partial pressure. The transmittance spectra of the films revealed that they were optically inhomogeneous. A model based on an inhomogeneous layer was applied to extract the refractive index and extinction coefficient from the transmittance and reflectance spectra.     

Structure and electrical properties of bismuth thin films prepared by flash evaporation method

Polycrystalline Bi thin films with thickness in the range 40-160 nm have been successfully deposited on glass substrates at 453 K by flash evaporation method for the first time. XRD and FE-SEM were performed to characterize their structure and surface morphology respectively. Electrical resistivity measurement was carried out in the temperature range 300-350 K. Hall coefficient, electron concentration and mobility were measured at 300 K. A distinctly oscillatory behavior has been observed for the electrical properties of the Bi thin films.     

CuInS2薄膜的单源热蒸发制备及其性能研究

本文以烧结合成的CuInS2粉末为原料,采用单源热蒸发技术在玻璃基底上沉积CuInS2薄膜。随着退火温度的升高,薄膜的结晶性能增强,表现出高度的(112)晶面择优取向,SEM观察显示:350℃退火后,薄膜致密,晶粒细小,大小为数十纳米。同时,热探针测试发现:薄膜的导电类型为弱N型。光学性能方面,当退火温度高于250℃时,CuInS2薄膜的禁带宽度为1.50 eV,接近吸收太阳光谱所需的理想禁带宽度值。     

热蒸发法制备SnS薄膜及其表征

用热蒸发技术在ITO玻璃基片上沉积SnS薄膜.通过对该薄膜进行结构、成分和表面形貌分析,表明它是具有正交结构的SnS多晶薄膜;相对于恒电流电沉积法制备的SnS薄膜来说,该薄膜颗粒更细,粒径在(60～100) nm,并且它的均匀性和对基片的附着力也更好.通过测量薄膜样品的反射和透射光谱,得到其直接禁带宽度Eg=1.34 eV,在基本吸收边附近的吸收系数大于2×104 cm-1.该薄膜的导电类型为p型,电阻率的数量级为10-2 Ω·cm.因此,用热蒸发技术制备出的SnS薄膜的质量和性能都比较理想,该薄膜非常适合做太阳能电池的吸收层.     

温度对电沉积的SnS薄膜的结构和性能的影响

在溶液的pH=2.7,离子浓度比Sn2 /S2O32-=1/5,沉积电位为-0.72～-0.75V(vs.SCE)的条件下,控制溶液的温度在30～50℃之间变化,用阴极恒电位电沉积法在ITO导电玻璃基片上沉积SnS薄膜.通过对薄膜的结构和光学性能研究,结果表明:溶液的温度越高,制备出的SnS薄膜更加致密,均匀,薄膜的衍射峰也越来越明显;同时SnS薄膜对光的吸收范围也向长波方向拓宽.     

Properties of cu-doped low resistive ZnSe films deposited by two-sourced evaporation

Two-sourced evaporation technique is used to prepare hard ZnSe films by controlling the evaporation rates of both Zn and Se at substrate temperature of 400 °C. The films are doped with Cu by immersion in the Cu(NO₃)₂-H₂O solution for different periods of time. The XRD has not shown a drastic change in the film structure while the electrical resistivity of the deposited film dropped from 10⁹ Ω-cm to about 1.6 Ω-cm for solution immersed films after heat treatment. Optical properties of deposited and doped films, such as film thickness, absorption coefficient and optical band gap have been calculated from the normal transmission spectra in the range of 300-2200 nm.The optical results show a decrease of the transmission and an increase of the refractive index and a slight shift in the optical band gap. Chemical composition of the Cu is determined by using absorption of immersed films. The composition of Cu is also compared with the composition detected by electron microprobe analyzer (EMPA).     

Characterization of copper oxide thin films deposited by the thermal evaporation of cuprous oxide (Cu2O)

Thin films of copper oxide were deposited by thermal evaporation of cuprous oxide (Cu₂O) powder. The substrates were either unheated or heated to a temperature of 300 °C. The films were also annealed in air at a temperature of 500 °C for 3 h. The films were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and UV-visible spectrophotometry. The effects of the substrate temperature and post-deposition annealing on the chemical, structural and optical properties of the films were investigated. As-deposited films on unheated substrates consisted of mixed cupric oxide (CuO) and Cu₂O phases, with a higher concentration of the Cu₂O phase. However, the films deposited on heated substrates and the annealed films were predominantly of the CuO phase.     

Y2O3 stabilized ZrO2 thin films deposited by electron-beam evaporation: Optical properties, structure and residual stresses

This paper describes the preparation and the characterization of Y₂O₃ stabilized ZrO₂ thin films produced by electric-beam evaporation method. The optical properties, microstructure, surface morphology and the residual stress of the deposited films were investigated by optical spectroscopy, X-ray diffraction (XRD), scanning probe microscope and optical interferometer. It is shown that the optical transmission spectra of all the YSZ thin films are similar with those of ZrO₂ thin film, possessing high transparency in the visible and near-infrared regions. The refractive index of the samples decreases with increasing of Y₂O₃ content. The crystalline structure of pure ZrO₂ films is a mixture of tetragonal phase and monoclinic phase, however, Y₂O₃ stabilized ZrO₂ thin films only exhibit the cubic phase independently of how much the added Y₂O₃ content is. The surface morphology spectrum indicates that all thin films present a crystalline columnar texture with columnar grains perpendicular to the substrate and with a predominantly open microporosity. The residual stress of films transforms tensile from compressive with the increasing of Y₂O₃ molar content, which corresponds to the evolutions of the structure and packing densities.     

Electrical and optical properties of copper-complexes thin films grown by the vacuum thermal evaporation technique

In this work, the synthesis and characterization of molecular materials formed from K₂[Cu(C₂O₄)₂], 1,8-dihydroxyanthraquinone and its potassium salt are reported. These complexes have been used to prepare thin films by vacuum thermal evaporation. The synthesized materials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), fast atomic bombardment (FAB+) mass and ultraviolet–visible (UV–vis) spectroscopy. Electrical transport properties were studied by dc conductivity measurements. The electrical activation energies of the complexes, which were in the range of 0.36–0.65 eV, were calculated from their Arrhenius plots. Optical absorption studies in the 100–1100 nm wavelength range at room temperature showed thin films' optical band gaps in the 2.3–3.9 eV range for direct transitions. On the other hand, strong visible photoluminescence (PL) at room temperature was noticed from the thermally-evaporated thin solid films. The PL of all investigated samples were observed with the naked eye in a bright background. The PL and absorption spectra of the investigated compounds are strongly influenced by the molecular structure and nature of the organic ligand.     

Microstructure and thermoelectric properties of Sn-doped Bi2Te2.7Se0.3 thin films deposited by flash evaporation method

(Bi_1 − xSn_x)₂Te_2.7Se_0.3 thermoelectric thin films with thickness of 800 nm have been deposited on glass substrates by flash evaporation method at 473 K. The structures, morphology of the thin films were analyzed by X-ray diffraction and field emission scanning electron microscopy respectively. Effects of Sn-doping concentration on thermoelectric properties of the annealed thin films were investigated by room-temperature measurement of Seebeck coefficient and electrical resistivity. The thermoelectric power factor was enhanced to 12.8 μW/cmK² (x = 0.003). From x = 0.004 to 0.01 Sn doping concentration, the Seebeck coefficients are positive and show p-type conduction. The Seebeck coefficient and electrical resistivity gradually decrease with increasing Sn doping concentration.     

Structural studies on some doped CdS thin films deposited by thermal evaporation

The influence of the Mn, Se and Sb impurities on the structure and morphology of CdS thin films grown on p⁺ Si wafers was studied. The starting powders were mixed in the same molar ratios (0.3%) and deposited in the same conditions by vacuum thermal evaporation. X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and reflectance studies made on thermal treated thin films (573 K, 2 h in air) evidenced that thin films have a hexagonal oriented structure, and that dopants enter into the CdS lattice merely by substitution. The dopant nature influences the thin film thickness and chemical composition. The doped CdS thin films have roughness in nanometer region and a reflectivity lower than 40%. Silicon substrate acts as a template and favors the retention of Mn and scatters the Sb dopants. The CdS:Se thin film is thicker than CdS:Mn and CdS:Sb ones and is a mixture of doped and undoped nanocrystals.     

Diffusion-limited evaporation of thin polar liquid films

The stability of evaporating very thin films of a polar liquid is investigated. The microscopic interaction with the substrate and capillarity are taken into account in a lubrication equation. The stability of a flat interface is studied when evaporation is limited by the diffusion of the vapour in the gas phase. The evaporation rate is computed and evaporation is shown to be stabilizing. A stability phase diagram is obtained. A weakly nonlinear analysis leads to a film-thickness amplitude equation that is non local in space. Physical consequences of the results are eventually discussed.     

Electromagnetic interference shielding effectiveness of nanoreinforced polymer composites deposited with conductive metallic thin films

The effect of using conductive metallic thin films deposited on high density polyethylene (HDPE) and styrene butadiene copolymer (SBC) in conjunction with carbon nanofiber (CNF) reinforcement of HDPE and SBC was investigated in order to improve the electromagnetic interference shielding effectiveness (EMI SE) of the structures. Thin films of copper, silver and aluminum were deposited by thermal evaporation onto the polymeric matrices and its composites (0-20 wt.% of CNFs). Results show a synergistic effect of the two approaches (metallic coating and CNF reinforcement) toward improving the EMI SE. The chemical composition, surface morphology, carbon nanofiber distribution, thickness and microstructure of metallic coated polymers are examined using X-Ray Diffraction and Scanning Electron Microscopy.     

Preparation and properties of ZnO thin films deposited by sol-gel technique

Zinc oxide (ZnO) thin films were deposited on (100) Si substrates by sol-gel technique. Zinc acetate was used as the precursor material. The effect of different annealing atmospheres and annealing temperatures on composition, structural and optical properties of ZnO thin films was investigated by using Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy and photoluminescence (PL), respectively. At an annealing temperature of 400°C in N₂ for 2 h, dried gel films were propitious to undergo structural relaxation and grow ZnO grains. ZnO thin film annealed at 400°C in N₂ for 2 h exhibited the optimal structure and PL property, and the grain size and the lattice constants of the film were calculated (41.6 nm, a = 3.253 ? and c = 5.210 ?). Moreover, a green emission around 495 nm was observed in the PL spectra owing to the oxygen vacancies located at the surface of ZnO grains. With increasing annealing temperature, both the amount of the grown ZnO and the specific surface area of the grains decrease, which jointly weaken the green emission. Translated from Journal of Lanzhou University (Natural Science), 2006, 42(1): 67–71 [译自: 兰州大学学报 (自然科学版)]