Structural and optical properties of CdS/PEO nanocomposite solid films

In this paper solution mixing and casting of Cd(NO₃)₂·4H₂O and poly(ethylene oxide) (PEO) at different molar ratios (1:100–1:600) followed by hydrogen sulfide treatment were employed to fabricate solid films of cadmium sulfide (CdS)/polyethylene oxide (PEO) nanocomposites. The nanocomposites were found to exhibit uniform distribution of CdS nanoparticles in the polymer matrix without any additional capping agent. Systematic investigations on the role of PEO on the optical properties of CdS are presented. The optical properties of the composites examined by UV–vis absorption spectroscopy show that the band gap of CdS nanoparticles increases from 2.45 eV to 2.54 eV with decreasing concentration of CdS in PEO films. X-ray diffraction pattern shows the broadening in shape of the PEO peaks which is induced by the CdS particles in PEO matrix. The CdS particle sizes ranging from 10 to 20 nm are clearly seen in a transmission electron microscope (TEM). The X-ray photoelectron spectroscopic studies (XPS) also confirm the presence of CdS in PEO. Fourier transform infrared spectroscopy studies using attenuated total reflectance (FTIR-ATR) indicate the influence of Cd²⁺ ion on C–O–C stretching in PEO and confirm the presence of CdS nanoparticles within PEO. Photoluminescence spectroscopy (PL) shows the broad emission due to the presence of surface trapped carrier states.     

低温磁控溅射制备CdS薄膜的结构和光学特性

用磁控溅射的方法在透明导电氧化物衬底上制备了CdS薄膜,制备时的衬底温度为30~200℃.X射线衍射测试结果表明在这一条件下制备的CdS薄膜是六角纤锌矿的多晶结构.扫描电子显微镜结果显示薄膜具有较好的晶体质量,这一结论也和拉曼光谱、紫外-可见吸收光谱、光致发光光谱的结果一致.拉曼光谱显示CdS薄膜内部的压应力随着制备温度的提高而增大.     

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。     

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.     

Enhancement in the optical and electrical properties of CdS thin films through Ga and K co-doping

In the presented work, Ga-doped CdS and (Ga-K)-co-doped CdS thin films are grown on glass substrates at a temperature of 400 °C through spray pyrolysis. Influence of K-doping on structural, morphological, optical and electrical characteristics of CdS:Ga thin films are examined. K level is changed from 1 at% to 5 at% for CdS:Ga samples just as Ga concentration is fixed 2 at% for all CdS thin films. It is observed from the X-ray diffraction data that all the samples exhibit hexagonal structure and an increase level of K in Ga-doped CdS samples causes a degradation in the crystal quality. Energy-dispersive X-ray spectroscopy measurements illustrate that the best stoichiometric film is acquired when K content is 2 at% in Ga-doped CdS films. Optical transmission curves demonstrate that CdS:Ga thin films exhibit the best optical transparency in the visible range for 4 at% K content compared to other specimens. A widening in the optical bandgap is unveiled after K-dopings. It is obtained that maximum band gap value is found as 2.45 eV for 3 at%, 4 at% and 5 at%. K -dopings while Ga-doped CdS thin films display the band gap value of 2.43 eV. From photoluminescence measurements, the most intensified peak is observed in the deep level emission after incorporation of the 4 at% K atoms. As for electrical characterization results, the resistivity reduces and the carrier density improves with the increase of K concentration from 1 at% to 4 at%. Based on all the data, it can be deduced that 4 at% K-doped CdS:Ga thin films show the best optical and electrical behavior, which can be utilized for solar cell devices.     

硫化物钝化对InAs纳米线光学特性的影响

针对InAs纳米线表面氧化造成的发光效率低的问题,采用十八硫醇和硫化铵钝化了由化学气相沉积设备生长的闪锌矿结构的InAs纳米线。对硫化物钝化前后的InAs纳米线进行温度依赖的光致发光光谱测试。实验结果表明,十八硫醇和硫化铵钝化的InAs纳米线在25 K温度下的发光效率与未钝化的InAs纳米线相比分别提高了～6倍和～7倍,此外,可以在室温下探测到硫化铵钝化的InAs纳米线的光致发光,这为未来基于InAs纳米线的中红外纳米光子器件提供了可能性。     

CdS amorphous thin films photochemical synthesis and optical characterization

Thin amorphous nanostructured CdS films were photochemically obtained via direct UV radiation (λ=254 nm) of complex Cd[(CH₃)₂CHCH₂CH₂OCS₂]₂ on Si(1 0 0) and ITO-covered glass substrate by spin coating. Thin cadmium xanthate complex films’ UV photolysis results in loss of all ligands from the coordination sphere. X-ray photoelectron spectra for as-deposited CdS thin films show the most representative signals of Cd 3d_5/2 located at 405 eV, Cd 3d_3/2 located at 412 eV and a small signal S 2p located at 162 eV. The surface morphology of the films was examined via atomic force microscopy. This can be described as a fibrous-type surface without structural order, which is characteristic of an amorphous deposit. The optical band gap value was 2.85 and 3.15±0.1 eV.     

偶氮掺杂光学薄膜非线性光学特性研究

为探索温度不同及掺杂浓度不同对极化聚合物二次谐波产生（SHG）的影响,用实时电晕极化装置对一种偶氮主客体掺杂薄膜进行了研究,结果显示,对于这种主客体掺杂体系,二次谐波产生强度随温度先增大后减小,存在一个最佳值;在最佳极化温度下,随着偶氮材料掺杂浓度的提高,二次谐波产生强度,先增大后减小。结合紫外-可见吸收谱对结果进行分析,对产生这种现象的物理机制提出一种新的解释：随着掺杂浓度的提高分子间作用不可忽略,使得偶氮材料的一阶超极化率的大小发生变化,导致二次谐波强度发生变化。     

Gamma irradiation induced effects on optical properties and single oscillator parameters of Fe-doped CdS diluted magnetic semiconductors thin films

Gamma radiation (100–500 kGy) induced effects on optical properties and single oscillator parameters of nanocrystalline diluted magnetic semiconductor thin films Cd_1−xFe_xS (x=0.1, 0.15 and 0.2) with different compositions prepared by electron evaporation techniques have been studied. The optical characterization of the films has been carried out from spectral transmittance and reflectance obtained by double beam spectrophotometer in the wavelength range from 190 to 2500 nm. It is clearly shown that the direct optical band gap decreases with the increase in gamma radiation dose. This is attributed to the defect number growth. The refractive index and extinction coefficient have shown clear changes with irradiation and found to increase with the increase of the doses of γ radiation. This post-irradiation increase of the refractive index was interpreted in terms of the film density increase due to ionization and/or atomic displacements. Furthermore, the dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single oscillator model. The oscillator parameters, the single oscillator energy E_o, the dispersion energy E_d, the static refractive index n₀, average interband oscillator wavelength λ_o, and the average oscillator strength S_o, were estimated and revealed pronounced changes with irradiation. The observed changes in optical properties and single oscillator parameters clearly indicate the possibility of using Fe doped CdS thin films as a material for gamma radiation dosimeters     

Optical properties of chemical bath deposited CdS thin films

CdS thin films have been prepared by chemical bath deposition. As-deposited films are cubic and show a sulfur deficiency. From the transmittance and reflectance data analysis direct band gaps (E_g) ranging from 2.180 to 2.448 eV have been obtained. Air and vacuum annealed samples show a decrease in the band gap. The refractive index (n) lies in the range 1.61–2.34. A dependence of band gap on composition has been observed and the possible reasons are discussed.     

Research on structural characteristics of large-scale CdS thin films deposited by CBD under low ammonia condition

Cadmium sulfide (CdS) buffer layers with the scale of 10 cm×10 cm are deposited by chemical bath deposition (CBD) with different temperatures and thiourea concentrations under low ammonia condition. There are obvious hexagonal phases and cubic phases in CdS thin films under the conditions of low temperature and high thiourea concentration. The main reason is that the heterogeneous reaction is dominant for homogeneous reaction. At low temperature, CdS thin films with good uniformity and high transmittance are deposited by adjusting the thiourea concentration, and there is almost no precipitation in reaction solution. In addition, the low temperature is desired in assembly line. The transmittance and the band gap of CdS thin films are above 80% and about 2.4 eV, respectively. These films are suitable for the buffer layers of large-scale Cu(In,Ga)Se2 (CIGS) solar cells.     

溶液PH值对CdS薄膜结构特性的影响

采用化学水浴沉积(CBD)工艺在玻璃衬底上制 备CdS薄膜,研究溶液PH值对CdS 薄膜结构特性的影响。薄膜的厚度、组份、晶相结构和表观形貌分别由台阶仪、X射线荧光 光谱(XRF)、X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)来表征。溶液的 PH值为11.26、 11.37和11.48时,CdS薄膜的晶相以六方相为主,薄膜的厚度先增大后减小; PH值为11.62、11.66时,薄膜的晶相以立方相为主,薄 膜的厚度进一步减小。同时,随着溶液PH值 增大,CdS薄膜的晶格常数也逐渐增大。两种晶相的CdS薄膜缓冲层与CIGS薄膜分别构成异 质 对形成异质结时的晶格失配分别为32.297%和1.419%,界面态密度分别为2.792×10¹⁴和8.507×10¹²,因此高效CIGS薄 膜太阳电池更需要立方相的CdS薄膜。     

Structure and optical properties of SiN x : H films with Si nanoclusters produced by low-frequency plasma-enhanced chemical vapor deposition

The SiN _x : H films with compositions differently deviating from the stoichiometric proportion are produced by low-frequency plasma-enhanced chemical vapor deposition at the temperatures 100 and 380°C. Deviations from the stoichiometric composition are varied by varying the ratio between the ammonia and monosilane fluxes from 0.5 to 5. The films are studied by ellipsometry, Raman spectroscopy, infrared absorption spectroscopy, and luminescence measurements. In the SiN _x : H films (x < 4/3), amorphous silicon clusters were found. According to estimations, only a small fraction of excess silicon coalesces into clusters, and an increase in the substrate temperature stimulates clustering. It is found that, with increasing the content of excess silicon in the films, the photoluminescence peak shifts to longer wavelengths.     

双层CdS／CdSe光电导薄膜的制作和光电特性

提出并采用真空热蒸发技术制备了一种新型的多元掺杂（Ｃｌ，Ｃｕ）敏化的ＣｄＳ／ＣｄＳｅ双层光电导薄膜。研究了这种光电导薄膜的暗电导和亮电导、响应时间，以及光谱响应等主要光电特性与初始材料比例、掺杂浓度和Ｃｌ／Ｃｕ比例等工艺参数的关系。实验表明：适宜的掺杂浓度和Ｃｌ／Ｃｕ比例可使暗电导降低而亮暗电导比提高，响应时间比未掺杂薄膜的显著降低；而光谱响应特性则可以通过控制ＣｄＳ／ＣｄＳｅ之比加以优化。     

CdTe-HgCdTe叠层太阳电池CdS窗口层透射光谱性能研究

CdS窗口层光谱透射率的提高对CdTe-HgCdTe叠层太阳电池有效利用入射太阳光并增大电池的短路电流密度有重要的影响。通过研究化学水浴法、近空间升华法和磁控溅射法制备的CdS薄膜在CdCl2退火前后的光谱平均透过率和短路电流密度损失表明:在光谱区520~820 nm,化学水浴法制备的CdS薄膜在退火前后具有最高的光谱平均透过率,对应的CdTe顶电池有最小的短路电流密度损失;在光谱区820~1150和520~1150 nm,磁控溅射法制备的CdS薄膜在退火前后均具有最高的光谱平均透过率,对应的HgCdTe底电池和CdTe-HgCdTe叠层太阳电池有最小的短路电流密度损失。在光谱区520~820、820~1150和520~1150 nm,CdCl2退火可以显著增大CdS薄膜的光谱平均透过率,降低对应CdTe顶电池、HgCdTe底电池和CdTe-HgCdTe叠层电池的短路电流密度损失。     

An optical study of alumina films thermal evolution upon ammonia annealing

The physical and structural evolution of alumina films deposited by ALCVD annealed at high temperatures in N₂ has been studied.Low temperature post deposition treatments in NH₃ (PDN) have been performed to evaluate the impact of nitrogen incorporation in the alumina film on its thermal stability. Thermal evolution has been studied by deep UV spectroscopic ellipsometry and grazing X-ray reflectance techniques. AFM measurements were also performed to confirm and complete the ellipsometric and GXR analysis.The change of the crystalline structure was detected by ellipsometry by the different UV refractive index, while the GXR provided a unique thickness evaluation.It was therefore possible to determine the layer densification after the thermal treatment and the impact of the PDN on the transition temperature.     

CdS微晶掺杂TiO2—SiO2复合薄膜的非线性光学特性

采用溶胶－凝胶方法在普通的载玻片上制备了ＣｄＳ微晶掺杂的ＴｉＯ２－ＳｉＯ２复合薄膜。用正硅酸乙酯、钛酸丁酯、醋酸镉作原料，比较了硫脲和硫化乙氨的硫化作用。不同热处理温度、时间的吸收光谱表明，薄膜中存在着量子尺寸效应。采用Ｚ－Ｓｃａｎ技术测量了薄膜的非线性吸收及非线性折射率。     

Molecular heterostructure devices composed of langmuir-blodgett films of conducting polymers

Organic heterostructures have been fabricated by alternating the deposition of monoand multilayers of undoped poly(3-hexylthiophene) and doped polypyrrole prepared by the Langmuir-Blodgett technique. The dopant profiles of the structures have been electrically characterized by incorporating the polymer layers as the active semiconductive material into metal-insulator-semiconductor and Schottky barrier device configurations. The dopant concentrations were evaluated by capacitance-voltage measurements. The results indicate modulated dopant profiles and a possible transfer of dopants. The dopant concentrations differ by about an order of magnitude between the undoped and doped layers. The Schottky barriers become thinner the closer the doped polypyrrole monolayer lies to the Schottky electrode.     

A study of the physical properties of sprayed CdS thin films

CdS films have been prepared by spray pyrolysis and characterized by several methods. The spray solution is made of cadmium chloride or cadmium acetate and thiourea. Optical and compositional properties and structure of the CdS films have been investigated. An analysis of the film's structure, preferred cyrstallographic orientation and presence of impurity phases have been obtained using X-ray diffraction technique as well as infrared spectroscopy. The visible absorption measurements have been carried out for the study of the impurity phases. Quantitative Auger analysis shows the composition of the spray solution and a post-spray heat treatment have also been investigated.