Preparation and characterization of ZnS thin films by the chemical bath deposition method

ZnS thin films prepared on quartz substrates by the chemical bath deposition (CBD) method with three type temperature profile processes have been investigated by X-ray diffraction, scanning electron microscope, energy dispersive X-ray analysis and light transmission. One is a 1-step growth process, and the other is 2-steps growth and self-catalyst growth processes. The surface morphology of CBD-ZnS thin films prepared by the CBD method with the self-catalyst growth process is flat and smooth compared with that prepared by the 1-step and 2-steps growth processes. The self-catalyst growth process in order to prepare the particles of ZnS as initial nucleus layer was useful for improvement in crystallinity of ZnS thin films prepared by CBD. ZnS thin films prepared by CBD method with self-catalyst growth process can be expected for improvement in the conversion efficiency of Cu(InGa)Se₂-based thin film solar cells by using it for the buffer layer.     

Fabrication and characterization of highly c-axial oriented ZnO films by chemical solution deposition

Highly c-axial oriented ZnO thin films were successfully fabricated on glass substrates at a very low pre-heating temperature by chemical solution deposition using polyvinyl alcohol (PVA) as the solvent. Effect of deposition parameters on the crystalline of ZnO films was investigated including atmosphere, pre-treating temperature and annealing temperature. It was found that all the samples were c-axial oriented regardless of growth conditions, attributing to the dominating mechanism of the PVA-Zn network. In addition, the optical properties of ZnO films were correlated with the surface morphology.     

化学水浴法制备ZnS薄膜光学性能

利用薄膜分析系统测量不同沉积时间制备的ZnS薄膜透射谱,通过分析薄膜透射谱,来确定ZnS薄膜光学常数和禁带宽度.实验结果表明,在线性生长阶段,薄膜的沉积速率大约为1 nm/min,具有很好的线性关系,沉积0.5 h的ZnS薄膜在可见光范围内光透过率为82%左右.     

Indium selenide microrod films: chemical bath deposition from acidic bath

Films of indium selenide was deposited onto glass and indium tin oxide coated glass substrates in acidic medium using chemical bath deposition at room temperature. Indium sulphate and sodium selenosulphate were used as precursors of In³⁺ and Se^2?, respectively. The structural, surface morphological and optical properties of the deposited films were studied. Diffractograms in structural study revealed the deposited material is In₂Se₃ films. Controlled bath conditions resulted in the evolution of the In₂Se₃ microrod-like morphology. The optical band gap of the film was found to be 1.7 eV.     

Multiple dip deposition of CdS films prepared by oscillating chemical bath

Highly oriented CdS thin films with thicknesses greater than 1 μm were deposited using the oscillating chemical bath deposition technique with multiple dips at 75 °C, and from 15 to 75 min as deposition times. Samples with different thicknesses were deposited by repeating the chemical deposition process one, two and three times. All CdS films present the α-greenockite hexagonal structure with (002) as the preferential orientation. Band-gap energy values ranged from 2.35 to 2.42 eV, being the smaller value for the two dip processes. Energy dispersion spectroscopy measurements show good stoichiometry of the CdS films with 4.3 at.% as the maximum Cd variation.     

化学浴法Cu2S纳米晶薄膜的制备及其光学特性研究

利用化学浴沉积法,以EDTA为络合剂,CuSO4·5H2O和Na2S2O3为前驱体溶液制备了硫化亚铜纳米薄膜,用FESEM、XRD、光学显微镜研究了前驱体浓度、络合剂的浓度、溶液的pH值、反应温度等因素对硫化亚铜纳米薄膜的表面形貌、晶粒大小与晶体结构的影响.结果表明,在最佳的生长条件下可以制备晶粒匀一、结构致密的硫化亚铜纳米薄膜,紫外可见吸收光谱表明硫化亚铜薄膜具有一定的透光性,并对红外光有很好屏蔽的作用.     

Room temperature synthesis and characterization of polythiophene thin films by chemical bath deposition (CBD) method

Polythiophene thin films were deposited successfully on glass substrate by chemical bath deposition method using FeCl₃ as an oxidant and chloroform as solvent. The effect of oxidant concentration on the properties of polythiophene thin films was studied. The surface morphology was influenced by oxidant concentration and deposition time. The oxidation concentration also strongly affects the optical properties of the polythiophene thin films. The transmittance decreases while the absorption, band gap and refractive index increases due to increase in oxidant concentration.     

Kinetics of the chemical bath deposition of ZnSe films

Thin films of ZnSe were obtained by chemical bath deposition from a solution containing ZnCl₂, hydrazine (NH₂)₂H₂O, NH₃, and Na₂SSeO₃. The influence of the concentration of the components and of the temperature on the growth rate was studied. A hypothesis for a ZnSe formation process is proposed. The technological parameters for the preparation of thin dense films of sphalerite structure with a high transparency in the solar spectrum region are defined.     

CdS thin films growth by ammonia free chemical bath deposition technique

Cadmium Sulfide CdS thin films were deposited by chemical bath deposition technique using ethanolamine as complexing agent instead of commonly used ammonia to avoid its toxicity and volatility during film preparation. In order to investigate the film growth mechanism samples were prepared with different deposition times. A set of substrates were dropped in the same bath and each 30 minutes a sample is withdrawn from the bath, by this way all the obtained films were grown in the same condition. The films structure was analyzed by X rays diffraction. In early stage of growth the obtained films are amorphous, with increasing the deposition time, the films exhibits a pure hexagonal structure with (101) preferential orientation. The film surface morphology was studied by atomic force microscopy. From these observations we concluded that the early growth stage starts in the 3D Volmer-Weber mode, followed by a transition to the Stransky-Krastanov mode with increasing deposition time. The critical thickness of this transition is 120 nm. CdS quantum dots were formed at end of the film growth. The optical transmittance characterization in the UV-Visible range shows that the prepared films have a high transparency ranging from 60 to 80% for photons having wavelength greater than 600 nm.     

Structural analysis of indium sulphide thin films elaborated by chemical bath deposition

X-ray diffraction and scanning electron microscopy show that the crystalline state of indium sulphide thin films, elaborated by chemical bath deposition technique on various substrates, is strongly affected by deposition parameters (deposition time t_D, pH solution and thioacetamide concentration), as well as by annealing treatment.We show that β-In₂S₃ thin films grown on glass substrate during t_D=60 min, and annealed under nitrogen at 400 °C during 1 h are well crystallized according to the cubic structure with the preferential orientation (610). They have a good homogenity and crystallinity.     

Structural and optical properties of CdS thin films grown by chemical bath deposition

Cubic cadmium sulphide (CdS) thin films with (111) preferential orientation were prepared by chemical bath deposition (CBD) technique, using the reaction between NH₄OH, CdSO₄ and CS(NH₂)₂. The films properties have been investigated as a function of bath temperature and deposition time. Structural properties of the obtained films were studied by X-ray diffraction analysis. The structural parameters such as crystallite size have been evaluated. The transmission spectra, recorded in the UV visible range reveal a relatively high transmission coefficient (70%) in the obtained films. The transmittance data analysis indicates that the optical band gap is closely related to the deposition conditions, a direct band gap ranging from 2.0 eV to 2.34 eV was deduced. The electrical characterization shows that CdS films' dark conductivities can be controlled either by the deposition time or the bath temperature.     

Influence of the deposition parameters on the properties of orthorhombic SnS films by chemical bath deposition

Orthorhombic stannous sulfide (SnS) films were prepared by chemical bath deposition in which stannous dichloride (SnCl₂), ammonium citrate (C₆H₅O₇(NH₄)₃) and sodium thiosulfate (Na₂S₂O₃) were used as tin source, chelating reagent and sulfur source, respectively. The influence of the deposition temperatures and the concentration ratios of Na₂S₂O₃/SnCl₂ on the morphologies, compositions and electrical and optical properties of the SnS films were investigated. The results show that the compactness of the SnS films gets worse when the deposition temperature increases, while the compactness of the films gets better when the concentration ratio of Na₂S₂O₃/SnCl₂ increases. The compositions of the films (the molar ratio of S/Sn ranges from 46.7:53.3 to 48.9:51.1) are all close to the stoichiometric ratio of SnS, and the molar ratio of S/Sn in the films increases as the deposition temperature and the concentration ratio of Na₂S₂O₃/SnCl₂ increase. The optical bandgaps of the SnS films are in the range of 1.01 eV-1.26 eV. The dark conductivities and photo conductivities of the SnS films all increase as the deposition temperature and the concentration ratio of Na₂S₂O₃/SnCl₂ increase.     

Some physical properties of Sn-doped CdO thin films prepared by chemical bath deposition

Undoped and Sn-doped CdO thin films were prepared by the chemical bath deposition method by means of a procedure that improves the deposition efficiency. All as-grown films were crystallized in the cubic structure of cadmium peroxide (CdO₂) and transformed into CdO with a cubic structure after an annealing process. The as-grown films have a high resistivity (> 10⁶ Ω cm) and an optical bandgap around 3.6 eV. Undoped CdO displays an optical bandgap around 2.32–2.54 eV and has an electrical conductivity of 8 × 10^− 4 Ω cm. The Sn incorporation into CdO produces a blue shift in the optical bandgap (from 2.55 to 2.84 eV) and a decrease in the electrical conductivity.The deposition procedure described here gives colloid-free surface thin films as indicated by the surface morphology analysis.     

化学水浴中氨浓度对沉积ZnS薄膜的影响

用化学水浴法在玻璃衬底上沉积ZnS薄膜。采用XRD、SEM、nkd-薄膜分析系统对薄膜的形貌、结构和光学性能进行了分析，结果表明：当氨浓度〈1．50mol／L，可获得白点较少、平整性较好的非晶ZnS薄膜，在红移方向上很长的波段内透过率较好，可达95％以上，禁带宽度为3．81eV，折射率随波长的增加而减小，从2．32变化到1．92。有关化学水浴ZnS薄膜折射率的报道极少；当氨浓度〉1．50mol／L时，薄膜白点增多，易龟裂和剥落，结构是立方闪锌矿。     

Investigation of the ZnSxSe1-x thin films prepared by chemical bath deposition

The ZnS_xSe_1?x thin films were prepared by chemical bath deposition technique on glass substrates. The composition ‘x’ was varied from 0 to 1 by changing the concentration of thiourea and sodium selenosulphate in the precursors. The morphology, structural and optical properties of the ZnS_xSe_1?x thin films were characterized by energy dispersive spectrometer, scanning electron microscopy, X-ray diffraction and UV-Vis spectrophotometer. The results reveal that the ZnS_xSe_1?x films are cubic zinc blende structure for x = 0, 0.19, 0.25, and amorphous for x = 0.75, 1. The optical band gap of the ZnS_xSe_1?x films increase from 2.88 to 3.76 eV when the value of ‘x’ increases from 0 to 1. The growth mechanism of the ZnS_xSe_1–x films was discussed.     

Effects of complexing agent on CdS thin films prepared by chemical bath deposition

CdS films have been prepared by chemical bath deposition (CBD) without stirring using weak and strong complexing agents, i.e., ammonia and ethylenediaminetetraacetic acid (EDTA). The optical, structural, and morphological properties of chemical bath deposited CdS films have been investigated. When the complexing agent is ammonia, five peaks in the X-ray diffraction (XRD) patterns from the CdS film, respectively, correspond to the interplanar spacing of 3.5498, 3.3429, 3.1449, 2.0574, and 1.7487 Å, which are definitely ascribed to hexagonal structure; unfortunately, this hexagonal CdS film is with poor morphology and its optical property in the visible region is not desirable for the solar cells. While, when the complexing agent is EDTA, three diffraction peaks in the XRD patterns from the CdS film, respectively, correspond to the interplanar spacing of 3.1164, 2.6716, and 1.8507 Å, indicating that the film is of a cubic structure. Furthermore, the CdS film has good morphology and its optical property in the visible region is compliant to the requirements of solar cells.     

Investigation of CuInS2 thin film formation by a low-temperature chemical deposition method

Copper indium disulfide (CuInS(2), CIS) thin films were prepared by an alternative solution-based coating process adapted from the well-established aqueous metal salt/thiourea precursor system. The temperature for the decomposition of the precursors and the formation of CIS was lowered significantly to 130 °C by using the strongly coordinating solvent pyridine instead of the commonly used water. In addition, the influence of different annealing temperatures and concentrations of thiourea (TU) in the precursor solution on the obtained CIS samples was investigated. The films possess highly beneficial properties for photovoltaic applications, showing a chalcopyrite crystal structure, a high optical absorption (>10(4) cm(-1)) and an optical band gap between 1.45 and 1.51 eV. Chemical and morphological changes during the thin film formation were detected and explained by time-resolved simultaneous grazing incident small- and wide-angle X-ray scattering (GISAXS, GIWAXS) measurements, scanning electron microsccopy (SEM) and simultaneous thermogravimetry/mass spectroscopy (TG/MS).     

Study of trap levels by electrical techniques in p-type CuInSe2 thin films prepared using chemical bath deposition

CuInSe₂ thin films, prepared using the Chemical Bath Deposition (CBD) technique, were analysed using Thermally Stimulated Current (TSC) measurements in order to get a clear picture of the different trap levels present in it. As-prepared samples showed two trap levels: the prominent one was due to the presence of a Se vacancy, while the weak one was due to the presence of a Cu vacancy. After annealing in air, the Se vacancy disappeared and a new level appeared which is suspected to be due to adsorbed oxygen. But annealing in air does not affect the Cu vacancy. On the other hand, annealing in vacuum does not affect Se vacancy, but the presence of an Fe impurity was detected in this case. A possible explanation for this phenomenon is also discussed. The dark conductivity measurements were also conducted on as-prepared as well as annealed CuInSe₂ samples. These results are found to be in good agreement with the results obtained from TSC measurements.