不同衬底和CdCl2退火对磁控溅射CdS薄膜性能的影响

在科宁7059玻璃, FTO, ITO, AZO四种衬底上磁控溅射CdS薄膜, 并在CdCl₂+干燥空气380 ℃退火, 分别研究了不同衬底和退火工艺对CdS薄膜形貌、结构和光学性能的影响. 扫描电子显微镜形貌表明: 不同衬底原位溅射CdS薄膜的形貌不同, 退火后相应CdS薄膜的晶粒度和表面粗糙度明显增大. XRD衍射图谱表明: 不同衬底原位溅射和退火CdS薄膜均为六角相和立方相的混相结构, 退火前后科宁7059玻璃, FTO, AZO衬底上CdS薄膜有 H(002)/C(111) 最强衍射峰, ITO衬底原位溅射CdS薄膜没有明显的最强衍射峰, 退火后出现 H(002)/(111) 最强衍射峰. 紫外-可见分光光度计分析表明: AZO, FTO, ITO, 科宁7059玻璃衬底CdS薄膜的可见光平均透过率依次减小, 退火后相应衬底CdS薄膜的可见光平均透过率增大, 光学吸收系数降低; 退火显著增大了不同衬底CdS薄膜的光学带隙. 分析得出: 上述结果是由于不同衬底类型和退火工艺对CdS多晶薄膜的形貌、结构和带尾态掺杂浓度改变的结果. 关键词： CdS薄膜 磁控溅射 退火再结晶 带尾态     

Preparation of p-type CdS thin films and in situ dark conductivity in vacuum deposited CdS:Cu films

CdS:Cu thin films were prepared using a vacuum co-evaporation technique. The Hall measurements indicate that the conductivity characteristic of CdS thin films transformed from highly compensated in as-grown or weakly annealed materials to p-type conductive in strongly annealed materials. X-ray diffraction spectra show that as-deposited thin films were the hexagonal phase of CdS except the presence of copper for high Cu doping and the diffraction peaks of Cu disappeared after annealing. From the X-ray photoelectron spectroscopy we found the ionization of Cu atoms and the formation of an acceptor level. In situ dark conductivity in vacuum as-deposited CdS:Cu was performed in the temperature range between 27 and 250 °C. An abnormal temperature dependence of conductivity was observed in medium and heavily Cu-doped films. The formation of a p-type material at a certain temperature was also studied by the hot probe measurements, which indicates a complex compensation process in the Cu-doped CdS films.     

Low temperature ferromagnetic properties of CdS and CdTe thin films

The magnetic property in a material is induced by the unpaired electrons. This can occur due to defect states which can enhance the magnetic moment and the spin polarization. In this report, CdS and CdTe thin films are grown on FTO glass substrates by chemical bath deposition and close-spaced sublimation, respectively. The magnetic properties, which are introduced from oxygen states, are found in CdS and CdTe thin films. From the hysteresis loop of magnetic moment it is revealed that CdS and CdTe thin films have different kinds of magnetic moments at different temperatures. The M–H curves indicate that from 100 K to 350 K, CdS and CdTe thin films show paramagnetism and diamagnetism, respectively.A superparamagnetic or a weakly ferromagnetic response is found at 5 K. It is also observed from ZFC/FC curves that magnetic moments decrease with temperature increasing. Spin polarized density functional calculation for spin magnetic moment is also carried out.     

Photoluminescence studies on nanostructured cadmium sulfide thin films prepared by chemical bath deposition method and annealed at different temperatures

Nanostructured cadmium sulfide (CdS) thin films have been prepared by chemical bath deposition (CBD) method and after post deposition annealing of the thin films at different temperatures, photoluminescence (PL) property has been studied. The effects of various photoexcitation wavelengths on the PL behaviour of different annealed films of CdS were studied by recording the PL spectra. The intensity of PL, the profile of the PL spectra and the effects of photoexcitation wavelength depend drastically on the temperature of the post deposition annealing of the thin films. The XRD patterns of the films show the presence of both the hexagonal and cubic phases (mixed phases). The emission peak arises from the surface defects of the CdS nanocrystalline thin films. Significant modification in the surface morphology of the CdS films upon annealing has been observed from the FESEM images. The morphology of the thin films is expected to influence the PL behaviour of the CdS thin films. The quantum size effect and size dependant PL have been observed.     

对超声波作用下的化学浴沉积方法制备CdS薄膜的谱学分析

用化学浴沉积法制备了CdS薄膜 ,并研究了加超声波对CdS薄膜生长过程的影响。利用卢瑟福背散射 ,X 射线粉末衍射和扫描电子显微镜对薄膜的厚度、晶相和表面形貌进行了表征。结果表明施加超声波的作用能有效地改善薄膜的质量 ,制备出均匀、致密的有较好的晶体结构CdS薄膜。同时 ,通过时间的控制可以精确地控制薄膜在 5 0nm左右 ,以满足制备太阳能电池的特殊要求。     

Structural and optical properties of CdS thin films

CdS thin films are deposited onto glass substrates by vacuum evaporation at 373 K and the films are annealed at different temperatures. Rutherford backscattering spectrometry (RBS) and X-ray diffraction techniques are used to determine the thickness, composition, crystalline structure and grain size of the films. The films show a predominant hexagonal phase with small crystallites. The optical band gap of the films are estimated using the optical transmittance measurements. A decrease in the band gap is observed for the annealed films. The Raman peak position of the CdS A₁ (LO) mode did not change much whereas, the full width at half maximum (FWHM) is found to decrease with annealing.     

Electron microscopic study of thin CdS films

The results obtained by investigating the surface morphology and optical properties of thin CdS films formed on transparent glass and glass/indium-tin oxide (ITO) substrates via the chemical and electro-chemical methods are presented. Thin cadmium sulfide films are employed as optical windows in thin-film polycrystalline solar cells. Closely packed cadmium sulfide nanoparticles are observed on the conducting oxide (ITO) surface by means of atomic-force microscopy. Large particles (150–300 nm) comprise smaller particles with sizes of 20–30 nm. Thin CdS layers are characterized by a relatively high level of transmission (～60%) in the long-wavelength spectral region (520–600 nm).     

用一维光子带隙结构增强硫化镉双光子吸收研究

用真空镀膜方法制备了含有单个CdS缺陷层的具有不同周期和结构参量的TiO2／SiO2一维光子晶体。用抽运一探测技术研究了CdS缺陷层的双光子吸收（TPA）现象。实验结果表明：一维光子晶体中CdS缺陷层的双光子吸收显著增强。不同周期和结构参量的一维光子晶体中CdS缺陷层的双光子吸收系数不同。双光子吸收的增强来源于由光局域化导致的缺陷层的电场强度的增加。缺陷层电场强度与一维光子晶体的结构有关,如周期,光子带隙的位置与宽度及缺陷模式等因素都会影响缺陷层电场强度。采用四分之一波长的高低折射率介质层和与入射波长匹配的缺陷模可以得到最大的缺陷层电场强度。     

The comparison between CdS thin films grown on Si(111) substrate and quartz substrate by femtosecond pulsed laser deposition

Two kinds of cadmium sulfate (CdS) thin films have been grown at 600 °C onto Si(111) and quartz substrates using femtosecond pulsed laser deposition (PLD). The influence of substrates on the structural and optical properties of the CdS thin films grown by femtosecond pulsed laser deposition have been studied. The CdS thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL) and Raman spectroscopy. Although CdS thin films deposited both on Si(111) and quartz substrates were polycrystalline and hexagonal as shown by the XRD , SEM and AFM results, the crystalline quality and optical properties were found to be different. The size of the grains for the CdS thin film grown on Si(111) substrate were observed to be larger than that of the CdS thin film grown on quartz substrate, and there is more microcrystalline perpendicularity of c-axis for the film deposited on the quartz substrate than that for the films deposited on the Si substrate. In addition, in the PL spectra, the excitonic peak is more intense and resolved for CdS film deposited on quartz than that for the CdS film deposited on Si(111) substrate. The LO and TO Raman peaks in the CdS films grown on Si(111) substrate and quartz substrate are different, which is due to higher stress and bigger grain size in the CdS film grown on Si(111) substrate, than that of the CdS film grown on the amorphous quartz substrate. All this suggests that the substrates have a significant effect on the structural and optical properties of thin CdS films. PACS 81.15.Fg; 81.05.Ea; 78.20.-e; 78.67.-n; 42.62.-b     

氧对于在Ar/O氛围下用近空间升华法制备的CdS薄膜的影响

采用近空间升华法（CSS）在氩/氧气氛中制备了硫化镉（CdS）多晶薄膜.利用XRD,XPS,AFM,UV-VIS光谱和四探针技术等测试和分析手段系统研究了氧对薄膜的成分、结构、光学和电学等性质的影响.结果表明,用近空间升华法制备的CdS薄膜具有六方相结构,膜层致密、均匀,平均晶粒大小约为40 nm,富硫.氧掺入后部分与镉生成氧化镉,并随着氧含量的增加,薄膜的成分有趋于化学计量比的趋势,光学带隙加宽,光暗电导比增加.此外,还利用扫描电镜（SEM）观察了CdS/CdTe断面结合光谱响应（QE）的结果讨论了氧对CdS/CdTe界面互扩散的影响.发现,随着CdS薄膜制备气氛中氧分压的升高,CdS/CdTe界面的互扩散程度降低,有利于提高器件在500—600 nm波长范围内的光谱响应.认为,氧含量的增加不但使CdS薄膜在光伏应用方面的质量得到改善,而且CdTe太阳电池器件中的CdS/CdTe界面也得到了优化. 关键词： CdS多晶薄膜 近空间升华法 窗口层 界面     

反应前驱物中n(S)∶n(Cd)对CdS薄膜结构及发光特性的影响

采用化学水浴以CdCl2·H2O、CS( NH2)2、NH4Cl、NH3·H2O和去离子水作为反应前驱物制备CdS纳米晶薄膜.采用扫描电镜( SEM)、X射线衍射(XRD)、透射光谱和稳态荧光光谱,研究了反应前驱物中不同的n(S)∶n(Cd)对所制备的CdS薄膜的形貌、结构和光学性能的影响.结果表明:反应前驱物中n(S...     

AFM, XPS and RBS studies of the growth process of CdS thin films on ITO/glass substrates deposited using an ammonia-free chemical process

This paper deals with a detailed study of the growth stages of CdS thin films on ITO/glass substrates by chemical bath deposition (CBD). The chemical and morphological characterization was done through X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and atomic force microscopy (AFM) techniques. On the other hand, optical transmission and X-ray diffraction (XRD) measurements were performed in order to study the optical and structural properties of the films. The time, the chemistry, and morphology of the different stages that form the growth process by CBD were identified through these results. Furthermore, clear evidence was obtained of the formation of Cd(OH)₂ as the first chemical species adhered to the substrate surface which forms the first nucleation centers for a good CdS formation and growth. On the other hand, the ITO coating caused growth stages to occur earlier than in just glass substrates, with which we can obtain a determined thickness in a shorter deposition time. We were able to prove that CBD is a good technique for the manufacture of thin films of semiconductor materials, since the CdS film does not have any impurities. Completely formed films were transparent, uniform, with good adherence to the substrate, of a polycrystalline nature with a hexagonal structure. These results indicate that films obtained by CBD are good candidates to be applied in different optoelectronic devices.     

Structure and properties of ZnSe nanocomposite thin films

The structure and electrophysical and optical properties of semiconductor ZnSe nanocomposite thin films are studied. These films are obtained by discrete thermal evaporation in an ultrahigh vacuum. ZnSe films are synthesized in various structural states in the condensation temperature range 2–200°C. The optical spectra of these films are studied in the visible region.     

化学水浴法和磁控溅射法制备硫化镉薄膜的性能研究

以氯化铵、氯化镉、氢氧化钾和硫脲为反应物采用化学水浴法制备了硫化镉薄膜,为了作对比研究,采用射频磁控溅射以硫化镉为靶材,氩气为溅射气体,制备了硫化镉薄膜。采用X射线衍射、扫描电子显微镜和紫外-可见光光谱仪分别表征了硫化镉薄膜的结构、形貌和光学吸收特性。结果表明,采用以上两种方法制备的硫化镉均具有(002)择优取向,溅射法制备的硫化镉薄膜较致密,薄膜表面较光滑,平均晶粒尺寸在20～30nm;水浴法制备的硫化镉薄膜颗粒尺寸较小,缺陷较多。除了在短波段溅射所得硫化镉薄膜的透过率略差于水浴法所得硫化镉薄膜之外,溅射法制备的硫化镉薄膜的性能整体上优于水浴法制备的薄膜。两种方法制备的硫化镉薄膜的能隙在2.3～2.5eV。     

CdSyTe1-y多晶薄膜的制备及光谱表征

采用真空共蒸发法制备了CdSyTe1-y(0≤y≤1)多晶薄膜,并用X射线衍射谱(XRD)、能量色散谱(EDS)研究了CdSyTe1-y多晶薄膜的结构、组分。实验结果表明:石英振荡法监控的组分与EDS谱结果较为一致;当y<0·3时,CdSyTe1-y多晶薄膜为立方结构,当y≥0·3时,CdSyTe1-y多晶薄膜为六方结构。采用XRD线形分析法可计算出CdSyTe1-y多晶薄膜晶粒大小约20～50nm。最后,用紫外-可见-近红外谱(UV-Vis-NIR),测得300～2500nmCdSyTe1-y多晶薄膜的透过率曲线,并结合一阶Sellmeier模型的折射率色散关系,表征了CdSyTe1-y多晶薄膜的光学性质,获得了CdS0·22Te0·78多晶薄膜的光学厚度d～535nm,光能隙Eg～1·41eV,以及吸收系数α(λ)、折射率n(λ)等光学量。结果也表明,采用真空共蒸发法可以制备需要组分的CdSyTe1-y多晶薄膜,对CdSyTe1-y多晶薄膜光学性质的表征方法可推广到其他的半导体薄膜材料。     

CdTe太阳电池前电极SnO2:F/SnO2复合薄膜性能分析

减薄CdS窗口层是提高CdS/CdTe太阳电池转换效率的有效途径之一,减薄窗口层会对器件造成不利的影响,因此在减薄了的窗口层与前电极之间引入过渡层非常必要.利用反应磁控溅射法在前电极SnO₂:F薄膜衬底上制备未掺杂的SnO₂薄膜形成过渡层,并将其在N₂/O₂=4 ∶1,550 ℃环境进行了30 min热处理,利用原子力显微镜、X射线衍射仪、紫外分光光度计对复合薄膜热处理前后的形貌、结构、光学性能进行了表征,同时分析了复     

Effect of the laser fluence on structural and optical characterization of thin CdS films synthesized by femtosecond pulsed laser deposition

CdS thin films have been grown on Si(1 1 1) and quartz substrates using femtosecond pulsed laser deposition. X-ray diffraction, atomic force microscopy, photoluminescence measurement, and optical transmission spectroscopy were used to characterize the structure and optical properties of the deposited CdS thin films. The influence of the laser fluence (laser incident energy in the range 0.5–1.5 mJ/pulse) on the structural and optical characterizations of CdS thin films has been studied. The results indicate that the structure and optical properties of the CdS thin films can be improved as increasing the per pulse output energy of the femtosecond laser to 1.2 mJ. But when the per pulse output energy of the femtosecond laser is further increased to 1.5 mJ, which leads to the degradation of the structure and optical properties of the CdS thin films.     

Investigation of CdS and CdTe thin films and influence of CdCl2 on CdTe/CdS structure

CdTe/CdS heterojunction solar cell structure has been fabricated using simple, easy and low-cost methods. To fabricate this structure, CdS and CdTe thin films are deposited onto FTO-coated conducting glass substrates by chemical bath deposition (CBD) and electrodeposition method, respectively. The optimized growth conditions are chosen for both CdS and CdTe films by investigating the optical, structural and morphological properties of both the as-deposited and annealed films. Optical measurement showed that CdS films have higher transmittance and lower absorbance, and CdTe films have lower transmittance and higher absorbance in the near infrared region. The band gap of CdS films is estimated to lie in the range 2.29–2.41 eV and that of CdTe films is in the range 1.53–1.55 eV. X-ray diffraction (XRD) study reveals that CdS and CdTe films are polycrystalline with preferential orientation of (1 1 1) plane. Scanning electron microscopy (SEM) study reveals that both films are smooth, void-free and uniformly distributed over the surface of the substrate. Fabricated CdTe/CdS structure showed the anticipated rectifying behaviour, and the rectifying behaviour is observed to improve due to CdCl₂ treatment.     

CdS薄膜的化学沉积法制备及其特性的研究

用化学沉积方法在沉积温度为90 ℃下制备了CdS薄膜。研究了直接退火处理和涂敷CdCl₂甲醇饱和溶液后退火处理对CdS薄膜的影响。利用X射线衍射、扫描电子显微镜对薄膜的晶体结构、表面形貌进行了研究,发现没有任何处理的CdS薄膜没有明显的晶型;直接退火处理促进了CdS立方相的结晶,晶粒没有增大且生长出许多细小的晶粒;涂敷CdCl₂甲醇饱和溶液后退火处理不仅极大地促进了CdS六角相的结晶,而且晶粒增粗增大,表面更加光滑。用吸收光谱研究了薄膜的光学特性,发现退火使薄膜的禁带宽度变窄,涂敷CdCl₂甲醇溶液后退火处理使吸收边变陡和带尾变小。表明涂敷CdCl₂甲醇溶液退火处理明显改善CdS薄膜的结晶质量和光学性质。     

Optical and structural properties of CdS thin films grown by chemical bath deposition doped with Ag by ion exchange

In this work thin CdS films using glycine as a complexing agent were fabricated by chemical bath deposition and then doped with silver (Ag), by an ion exchange process with different concentrations of AgNO₃ solutions. The CdS films were immersed in silver solutions using different concentrations during 1 min for doping and after that the films were annealed at 200 °C during 20 min for dopant diffusion after the immersion on the AgNO₃ solutions. The aim of this research was to know the effects of different concentrations of Ag on the optical and structural properties of CdS thin films. The optical band gap of the doped films was determined by transmittance measurements, with the results of transmittance varying between 35% and 70% up to 450 nm in the electromagnetic spectra and the band gap varying between 2.31 and 2.51 eV depending of the silver content. X-ray photoelectron spectroscopy was used to study the influence of silver on the CdS:Ag films, as a function of the AgNO₃ solution concentration. The crystal structure of the thin CdS:Ag films was studied by the X-ray diffraction method and the film surface morphology was studied by atomic force microscopy. Using the ion exchange process, the CdS films’ structural, optical and electric characteristics were modified according to silver nitrate concentration used.