掺杂对CdS多晶薄膜电学性能的影响

利用近空间升华法制备CdS多晶薄膜,同时将薄膜在400℃下进行Cl-掺杂。利用光-电阻、暗电阻-温度关系等测试手段分析不同波长光照及温度对掺杂前后薄膜电学性能的影响。结果显示:在不同波长的光照下,薄膜显示出不同的电阻值,最小电阻出现在500 nm波长附近;在光、暗态转换过程中发现,掺杂对电阻弛豫时间影响较大,掺杂后最短响应时间由原来对应的青光向蓝光移动;掺杂后,薄膜光、暗电导增加,电导激活能减少。     

用共蒸发法制备AlSb多晶薄膜

采用元素共蒸发法结合退火处理制成了AlSb多晶薄膜.利用x射线衍射、透射光谱、暗电导温度关系等方法研究了薄膜的结构、光学和电学性质.发现540℃退火后得到的AlSb多晶薄膜呈立方相结构,间接跃迁光能隙为1.62eV,电导激活能约为0.33eV.研究结果表明,AlSb薄膜有可能成为新型太阳电池的重要材料.     

用共蒸发法制备AlSb多晶薄膜

采用元素共蒸发法结合退火处理制成了AlSb多晶薄膜.利用x射线衍射、透射光谱、暗电导温度关系等方法研究了薄膜的结构、光学和电学性质.发现540℃退火后得到的AlSb多晶薄膜呈立方相结构,间接跃迁光能隙为1.62eV,电导激活能约为0.33eV.研究结果表明,AlSb薄膜有可能成为新型太阳电池的重要材料.     

太阳电池中CdS多晶薄膜的微结构及性能

采用化学水浴法制备了CdS多晶薄膜，通过XRD，AFM，XPS和光学透过率谱等测试手段研究了CdS多晶薄膜生长过程中的结构和性能.结果表明，随着沉积的进行，薄膜更加均匀、致密，与衬底粘附力增强，其光学能隙逐渐增大，薄膜由无定形结构向六方(002)方向优化生长，同时出现了Cd(OH)2相.在此基础上，通过建立薄膜的生长机制与性能的联系，沉积出优质CdS多晶薄膜，获得了转化效率为13.38%的CdS/CdTe小面积电池.     

太阳电池中CdS多晶薄膜的微结构及性能

采用化学水浴法制备了CdS多晶薄膜,通过XRD,AFM,XPS和光学透过率谱等测试手段研究了CdS多晶薄膜生长过程中的结构和性能.结果表明,随着沉积的进行,薄膜更加均匀、致密,与衬底粘附力增强,其光学能隙逐渐增大,薄膜由无定形结构向六方(002)方向优化生长,同时出现了Cd(OH)2相.在此基础上,通过建立薄膜的生长机制与性能的联系,沉积出优质CdS多晶薄膜,获得了转化效率为13.38%的CdS/CdTe小面积电池.     

用磁控溅射和退火方法制备AlSb多晶薄膜

采用磁控溅射法在玻璃衬底上制备Al/Sb预制多层薄膜,然后将Al/Sb预制多层薄膜在退火炉中退火得到AlSb多晶薄膜.用X射线衍射(XRD)法测薄膜结构;用扫描电镜(SEM)测薄膜Al/Sb成分比,结果表明AlSb多晶薄膜具有单一的晶相、均匀的结构,以及粒径大约20nm的晶粒.根据电导率(lnσ)与温度(T)的关系得到电导激活能为0.21和0.321eV,为制备出适用于太阳电池的AlSb多晶薄膜奠定了一定的技术基础.     

电子束蒸发法制备CdS多晶薄膜及其结构和光学性质

采用电子束蒸发法在玻璃衬底上制备了具有较高结晶度和优异透光性能的CdS多晶薄膜,对制备样品的结构和光学性质进行了表征。结果表明,制备薄膜属于六方相多晶结构,沿（002）晶向择优取向生长。此外,随着衬底温度的升高,样品结晶质量先提高后降低,与薄膜厚度变化有关。紫外-可见透过谱显示,随着衬底温度的升高,薄膜的光吸收边趋于陡直,但光学带隙呈现波动变化,分布在2.389-2.448 eV之间。对样品进行光致发光谱测试表明,CdS薄膜发光锋展宽严重,仅在1.60 eV附近有一个微弱的红光发射。论文对上述实验结果进行了分析和讨论。     

CdS/CuInSe2多晶薄膜太阳电池参数分析

利用Rothwarf模型,通过理论计算,讨论了多晶CdS/CuInSe2薄膜太阳电池的掺杂浓度、厚度和晶粒尺寸对太阳电池转换效率的影响.结果表明太阳电池的吸收层掺杂浓度存在一个最佳值;晶粒半径、太阳电池厚度对电池效率有显著影响,但达到一定值后,对效率的影响可以忽略.     

化学水浴法制备CdS薄膜退火工艺的研究

基于化学水浴沉积法以硫脲为硫源,醋酸镉为镉源,氨水作为缓冲剂,制备太阳能电池用半导体薄膜硫化镉(CdS),研究不同的退火温度和是否涂敷CdCl2溶液对CdS薄膜的影响。采用X线衍射仪、电子扫描电镜和紫外/可见光分光光度计研究了不同退火工艺对硫化镉薄膜的结构、形貌及光学特性的影响。实验表明,悬涂CdCl2溶液退火处理可明显改善CdS薄膜的结晶及其光学性质,最佳退火温度为400℃,退火时间为60min。     

化学水浴法制备CdS薄膜退火工艺的研究

基于化学水浴沉积法以硫脲为硫源,醋酸镉为镉源,氨水作为缓冲剂,制备太阳能电池用半导体薄膜硫化镉(CdS),研究不同的退火温度和是否涂敷CdCl2溶液对CdS薄膜的影响。采用X线衍射仪、电子扫描电镜和紫外/可见光分光光度计研究了不同退火工艺对硫化镉薄膜的结构、形貌及光学特性的影响。实验表明,悬涂CdCl2溶液退火处理可明显改善CdS薄膜的结晶及其光学性质,最佳退火温度为400℃,退火时间为60min。     

Electronic properties of polycrystalline ceramic cadmium sulphide

An attempt has been made to explain the current transport mechanism of ceramic cadmium sulphide layers using a semiconductor-grain boundary-semiconductor barrier model. It is shown that a sine-hyperbolic current-voltage relationship holds good for ceramic cadmium sulphide. Grain boundary parameters like potential barrier (φ_B) and average one-electron trapping state density (N_T) in the grain boundary are determined experimentally for the first time for ceramic cadmium sulphide through the study of the current-voltage characteristics and zero-bias capacitances. The variation of φ_B and N_T with temperature (28°C to ?120°C) and bias voltage has also been investigated. It is concluded that the thermionic field emission components of current play a major role in the current transport characteristics of a ceramic cadmium sulphide layer.     

Optical properties of CdSxTe1−x polycrystalline thin films

Thin films of CdS_xTe_1−x (0≤x≤ 1) have been prepared by vacuum evaporation from solid solutions. Rutherford backscattering spectrometry has been used to determine the thickness of the films, which is in the range 8–50 nm, and x-ray diffraction analysis has been used to determine the phase. The refractive index and extinction coefficient of the films has been calculated from reflectance and transmittance measurements for the wavelength region 250–3200 nm. Polynomial functions are given for each sample, which describe the variation in refractive index and extinction coefficient over the entire wavelength range. Least squares fitting to the absorption spectra revealed that the films all have a direct band gap, although photon energies required for indirect transitions have also been found. CdS_0.8Te_0.2 is found to have the lowest absorption coefficient at energies greater than 2.1 eV.     

The electrical properties and device applications of homoepitaxialand polycrystalline diamond films

Electronic applications of semiconductor diamonds are addressed. Doping and electrical properties of these films, formation of low-resistive `ohmic' contacts, surface modification methods, and experimental device applications are discussed. Of particular interest are high-temperature (300°C) MOSFETs and metal contacts to CVD (chemical vapor deposition) diamond films which were used to fabricate high-temperature (580°C) Schottky diodes, rudimentary MESFETs, and blue light-emitting diodes (LEDs). The status of the emerging technology is reviewed with an emphasis on the areas of current research activity     

Structural and electrical properties of stable ni/cr thin films

The electrical and structural properties of nickel-chrome (NiCr) thin film resistors were studied for the effect of post-deposition annealing on stability. The temperature coefficient of resistance (TCR) of sheet resistivities in the range of 100 to 200 Ω/□ could be improved by both air and vacuum annealing to achieve 5 ± 5 ppm/°C over the temperature range of -180° C to +100° C. With stability tests, air annealing proved to be more favorable for stable TCR. Studies via SIMS and ESCA identified surface segregation of Cr whereas TEM micrographs revealed correlating structural transformation of the films upon annealing. An intentional impurity, Si, played an important role in achieving a low TCR.     

Structural and optical properties of polycrystalline CdS thin films deposited by electron beam evaporation

Highly crystalline and transparent cadmium sulphide(CdS) films were deposited on glass substrate by electron beam evaporation technique.The structural and optical properties of the films were investigated.The X-ray diffraction analysis revealed that the CdS films have a hexagonal structure and exhibit preferred orientation along the(002) plane.Meanwhile,the crystalline quality of samples increased first and then decreased as the substrate temperature improved,which is attributed to the variation in film thickness.UV-vis spectra of CdS films indicate that the absorption edge becomes steeper and the band gap present fluctuation changes in the range of 2.389-2.448 eV as the substrate temperature increased.The photoluminescence peak of the CdS films was found to be broadened seriously and there only emerges a red emission band at 1.60 eV.The above results were analyzed and discussed.     

Analysis on Conductivity of nc—Si：H Films

A conduction channel model is propsed to explain the high conductivity property of nc-Si:H.Detailed energy band diagram is developed based on the analysis and calculation ,and the conductivity of the nc-Si:H was then analysed on the basis of energy band theory.It is assumed that the conductivity of the nc-Si:H stems from two parts:the conductance of the interface,where the transport mechanism is identified as a thermal -assisted tunneling process,and the conductance along the channel around the grain,which mainly determined the high conductivity of the nc-Si:H.The conductivity of nc-Si:H is calculated and compared with the experiment data .The theory is in agreement with the experiment.     

A study of polycrystalline Cd(Zn,Mn)Te/Cds films and interfaces

Polycrystalline films of Cd_1-x Zn _x Te (x = 0–0.4) and Cd_1-x Mn _x Te (x = 0–0.25) were grown by MBE and MOCVD, respectively, on CdS/SnO₂/glass substrates to investigate their feasibility for solar cell applications. The compositional uniformity and interface quality of the films were analyzed by x-ray diffraction, surface photovoltage, and Auger depth profile measurements to establish a correlation between growth conditions and lattice constant, atomic concentration, and bandgap of the ternary films. MBE-grown polycrystalline Cd_1-x Zn _x Te films showed a linear dependence between Zn/(Cd + Zn) beam flux ratio, Zn concentration in the film, and the bandgap. Polycrystalline Cd_1-x Zn _x Te films grown at 300° C showed good compositional uniformity in contrast to compositionally non-uniform Cd_1-x Mn _x Te films grown by MOCVD in the temperature range of 420–450° C. The MBE-grown Cd_1-x Zn _x Te interface also showed significantly less interdiffusion compared to the MOCVD-grown Cd_1-x Mn _x Te/CdS interface, where preferential exchange between Cd from the CdS layer and Mn from the Cd_1-x Mn _x Te film was observed. The compositional uniformity of MOCVD-grown polycrystalline Cd_1-x Mn _x Te films grown on CdS/SnO₂/glass substrates was found to be a strong function of the growth conditions as well as the Mn source.     

Structure and electrical properties of polycrystalline SiGe films grown by molecular beam deposition

The structural and electrical properties of polycrystalline Si_0.5Ge_0.5 films 150 nm thick grown by molecular beam deposition at temperatures of 200–550°C on silicon substrates coated with amorphous layers of silicon oxynitride were studied. It is shown that the films consist of a mixture of amorphous and polycrystalline phases. The amorphous phase fraction decreases from ～50% in films deposited at 200°C to zero in films grown at 550°C. Subsequent 1-h annealing at a temperature of 550°C results in complete solid-phase crystallization of all films. The electron transport of charge carriers in polycrystalline films occurs by the thermally activated mechanism associated with the energy barrier of ～0.2 eV at grain boundaries. Barrier lowering upon additional annealing of SiGe films correlates with an increase in the average grain size.     

The structural,optical, and electrical properties of vacuum evaporated Cu-doped ZnTe polycrystalline thin films

We have studied the structural, optical, and electrical properties of thermally evaporated, Cu-doped, ZnTe thin films as a function of Cu concentration and post-deposition annealing temperature. X-ray diffraction measurements showed that the ZnTe films evaporated on room temperature substrates were characterized by an average grain size of 300Å with a (111) preferred orientation. Optical absorption measurements yielded a bandgap of 2.21 eV for undoped ZnTe. A bandgap shrinkage was observed for the Cu-doped films. The dark resistivity of the as-deposited ZnTe decreased by more than three orders of magnitude as the Cu concentration was increased from 4 to 8 at.% and decreased to less than 1 ohm-cm after annealing at 260°C. For films doped with 6–7 at.% Cu, an increase of resistivity was also observed during annealing at 150–200°C. The activation energy of the dark conductivity was measured as a function of Cu concentration and annealing temperature. Hall measurements yielded hole mobility values in the range between 0.1 and 1 cm²/V·s for both as-deposited and annealed films. Solar cells with a CdS/CdTe/ZnTe/metal structure were fabricated using Cudoped ZnTe as a back contact layer on electrodeposited CdTe. Fill factors approaching 0.75 and energy conversion efficiencies as high as 12.1% were obtained.