The optical properties of sprayed CdS thin films

In the study presented in this paper we attempted to interpret the reflectance and the transmittance of sprayed CdS films. Assuming a model based on multilayer film theory we showed that sprayed CdS film is a combination of multilayer stacks of crystallites and gaseous inclusions.     

Size dependent structural, optical and morphological properties of ZnS:Cu thin films

ZnS:Cu thin films have been deposited on glass substrate by a simple neutral pH solution synthesis route and chemical bath deposition technique. The copper concentration was varied between 0 and 0.1 M%. The X-ray diffraction and scanning electron microscope studies show the average size of the nanoparticles are below 4 nm (Bohr diameter). The effect of film thickness on the optical and structural properties has been studied. The optical absorption studies show the band gap energy of ZnS:Cu films decreases from 3.68 to 3.43 eV as thickness varied from 318.3 to 334.1 nm. The structural estimation shows the variation in particle size from 2.67 to 3.14 nm with thickness. The insignificant change in band gap may be due to the increase in particle size and quantum size effect.     

The influence of deposition parameters on the optical properties and growth of ZnS films

A vacuum automatic ellipsometer was used to observe and reveal the effect of the rate of deposition on the structural irregularities of ZnS films during growth.The high accuracy and sensitivity of this instrument were exploited for measuring the refractive index of ZnS films prepared at various rates of deposition and substrate temperatures.     

Effects of working pressure on morphology,structural, electrical and optical properties of a-InGaZnO thin films

Amorphous In–Ga–Zn–O (a-IGZO) thin films (～200 nm thickness) were deposited by radio-frequency (RF) magnetron sputtering on silicon and glass substrates at various working pressures (0.67–2.67 Pa) and a fixed oxygen-to-argon gas-flow ratio (O₂/Ar = 5%). The transparency of all of the films was more than 85% in the visible range. With increased working pressure, the surface morphology of the films, as observed under atomic force microscopy (AFM), became rough; the optical band gap, estimated by Tauc plot, increased, and the mobility and carrier concentrations, according to Hall measurement, decreased and increased, respectively. The resistivity of the films initially decreased (up to 2.00 Pa working pressure) and then increased (at 2.67 Pa). It is suggested that the electrical property changes were affected by the role of the oxygen vacancies, whether as effective donors or as scattering centers.     

Role of precursors on morphology and optical properties of ZnS thin films prepared by chemical spray pyrolysis

This study investigates the effect of different growth parameters on the structural and optical properties of ZnS thin films, prepared using spray pyrolysis. The films were prepared using different Zn:S ratios (between 1:1 and 1:6) and in different growth solutions: (A), zinc chloride and thiourea and (B) dehydrated zinc acetate and thiourea, both in distilled water.By varying the Zn:S ratio in the films, the optical properties (absorption and photoluminescence) show that different species are created during film growth. This was deduced from the wide emission band appearing in the green region of the photoluminescence spectra, and from the change in band gap, which varies between 3.2 and 3.5 eV. Films formed from solution (A) with a Zn:S ratio of 1:3 or 1:4 show the best morphology and transmission. ZnS has a wider band gap than other conventional II-VI semiconductors utilized in various electronic and optical devices and can be expected to provide a useful window layer of solar cells which leads to an improvement in overall efficiency by decreasing absorption loss.     

Grain growth and structural transformation in ZnS nanocrystalline thin films

Fabrication of ZnS thin films having similar stoichiometry at different substrate temperatures (T_S) e.g. 200 °C, 300 °C and 400 °C by means of RF magnetron sputtering method is presented. The films grown at T_S of 200 °C are in cubic zinc-blende phase and textured along (111) plane. The films deposited at T_S of 300 °C and 400 °C are in hexagonal wurtzite phase. The surface roughness and grain size of the films increase with increasing T_S. The ultra-violet and visible absorption studies show that the bandgap of films can be tailored by varying T_S, taking advantage of the structural transformation.     

The effect of annealing on structural, electrical and optical properties of nanostructured ZnS/Ag/ZnS films

In this paper a ZnS/Ag/ZnS (ZAZ) nano-multilayer structure is designed theoretically and optimum thicknesses of ZnS and Ag layers are calculated at 35 and 17 nm, respectively. Several conductive transparent ZAZ nano-multilayer films are deposited on a glass substrate at room temperature by thermal evaporation method. Changes in the electrical, structural, and optical properties of samples are investigated with respect to annealing in air at different temperatures. High-quality nano-multilayer films with the sheet resistance of 8 Ω/sq and the optical transmittance of 83% at 200 °C annealing temperature are obtained. The figure of merit is applied on the ZAZ films and their performance as transparent conductive electrodes are determined.     

The compositional and structural properties of sprayed SnO2:F thin films

Thin films of SnO₂ doped with fluorine were produced by the conventional spraying method using Corning 7059 glass substrates. The electrical and optical properties of these films were determined as a function of the substrate temperature T_s and dopant concentration in the basic spraying solution. The visible and near-IR transmittance as well as the electrical resistivity of the films decreased with an increase in the fluorine concentration. The best electro-optical properties (an average transmittance of 75% and an electrical resistivity of 10⁻³ Ω cm) were achieved for 250°C⩽T_s⩽350°C and fluorine concentrations (relative to tin) in the spraying solution of around 2 at.%. The surface texture of the films was investigated by scanning electron microscopy and optical microscopy. The fluorine content of the samples was analysed by secondary ion mass spectroscopy, Auger electron spectroscopy and electron spectroscopy for chemical analysis. Structural changes were studied using X-ray diffractometry. A systematic change in the intensity of the X-ray diffraction lines as a function of the fluorine content was observed. Theoretical calculations of the structure factors associated with the SnO₂ lattice if fluorine atoms are introduced into substitutional and interstitial positions were performed.     

Anisotropic optical properties of ZnS thin films with zigzag structure

ZnS sculptured thin films produced by thermal evaporation method using the glancing angle deposition technique at different deposition angles (0, 30, 60, 70 and 80\({^{\circ }}\)) are reported. The structural and optical properties of the prepared samples are investigated systematically using X-ray diffraction (XRD) and UV–VIS spectroscopy techniques. The XRD studies show cubic structure for the prepared films and deposition angle dependence of lattice constants, intrinsic stress, tensile stress and dislocation density. The obtained transmittance spectra in the range 380–850 nm for both s- and p-polarized light at normal incidence angle are used to study the s- and p-refractive indices and in-plane birefringence of the ZnS films. The maximum birefringence is evaluated at incident flux angle \(\alpha = 70{^{\circ }}\). Both the refractive index and packing density of the films decrease with increasing deposition angle, which confirm the structural inhomogeneity and porosity nature of the films.     

ZnS薄膜的水浴法制备及其光学性能

以酒石酸和柠檬酸钠为络合剂,采用水浴法(CBD)制备ZnS薄膜.利用X射线衍射(XRD)、X射线能谱仪(EDAX)、扫描电镜(SEM)、紫外-可见分光光度计(UV-vis)研究ZnS薄膜的结构、成分、形貌及光学性能.利用透射光谱计算了ZnS薄膜的光学禁带宽度.结果表明:ZnS薄膜呈立方相晶体结构,水浴沉积时间为3h的ZnS薄膜原子比Zn∶S为1∶0.85,薄膜表面均一致密,在可见光区有着好的透射性能,在300～800 nm的光谱范围内平均透射率达到80.8%,光学禁带宽度为3.78eV,适合作为太阳能电池过渡层.     

Intrinsic optical and structural properties of SrS thin films

SrS thin films were deposited by electron beam evaporation on heated silica substrates. The optical properties of the layers – complex refractive index and optical band gap –were derived from optical transmission spectra, measured by means of UV-VIS-NIR spectrophotometry. The influence of post-deposition annealing by rapid thermal processing (RTP) was studied. X-ray powder diffraction (XRD) was used to study the film crystal structure and preferential orientation.     

Electro-optical properties of thin ZnS films

The electro-optical properties of thin ZnS(Mn) films and d.c. luminescent diodes and triodes of the structure SnO_x-ZnS(Mn)-Cu_xS-ZnS(Mn)-Al have been studied. Cathodoluminescence and electroluminescence spectra of the films at various stages of production of the electroluminescent diodes were compared. It was found that the dependence of luminescence on voltage and time is exponential, as is the time dependence of the current.     

Effect of substrate temperature and precursor ratio on properties of thin ZnS films sprayed by improved method

Zinc sulphide (ZnS) thin films were prepared by improved spray pyrolysis (ISP) method. The ISP parameters, such as carrier gas flow rate, solution flow rate and substrate temperature, were controlled with an accuracy of ±0.25 lpm, ±1 ml/h and ±1 °C, respectively. The solution was sprayed in a pulsed mode. The substrate temperature was optimized by analyzing substrate temperature dependent properties of thin films. The thin film deposited at a temperature of 450 °C was dense and fairly smooth with satisfactory crystallinity and very small impurity content. The effect of precursor ratio in the solution on structural, compositional and optical properties of thin ZnS films, deposited at a temperature of 450 °C, was studied. A gradual increase in band gap energy from 3.524 eV to 3.634 eV, refractive index from 2.5 to 2.9 and dielectric constant from 6.6 to 8.7 were observed with the variation of solution precursor (Zn:S) ratio from (1:2) to (1:6). The structural and compositional studies support this kind of enhancement in optical properties. The results show that the thin ZnS film prepared by ISP at the substrate temperature of 450 °C from a solution with specific precursor ratio can be used for optoelectronic and photovoltaic applications.     

Mg掺杂ZnO薄膜的结构及其光学性能研究

利用射频磁控溅射技术在(100)Si和玻璃衬底上沉积系列Mg掺杂ZnO(x=0~0.20)薄膜,XRD分析结果表明,Zn1-xMgxO薄膜均为六角纤锌矿结构,薄膜呈现出c轴择优生长特性,但随着x值的增加,晶格常数c逐渐减小。当x=0.20时,薄膜出现(100)面衍射峰,薄膜的c轴择优生长特性减弱。SEM分析表明,x=0.10时,薄膜表面平坦光滑,晶粒大小均匀,结构更加致密,结晶质量最佳。紫外可见光透射光谱表明,Mg的掺入提高薄膜在可见光范围内的透过率;同时增大了薄膜的禁带宽度;室温PL谱分析显示所有薄膜均出现了紫外发射峰和蓝光发射带,且紫外发射峰和蓝光发光带都随x值的增加而蓝移。     

Characterization of optical, electrical and structural properties of silverphthalocyanine thin films

Silverphthalocyanine thin films are deposited on to glass substrates by thermal evaporation technique. Optical data have been obtained from both absorption and reflectivity spectra over the wavelength range 350–900 nm. The absorption coefficient α and extinction coefficient k are estimated from the spectrum. The mechanism of optical absorption follows the rule of direct transition. Using α and k, the refractive index and the dielectric constants are determined. Electrical conductivity studies are done at different substrate temperatures and using the Arrhenius plot the activation energy in the intrinsic region and impurity region is estimated. From the X-ray diffractograms of AgPc thin films subjected to heat treatments the variation of grain size is also studied. The scanning electron microscopy images are taken to study the surface morphology of the films. Silver phthalocyanine thin film is expected to find application in the fabrication of organic transistors and LED devices.     

Thickness dependence of structural, electrical and optical properties of sprayed ZnO:Cu films

ZnO:Cu thin films have been deposited by spray pyrolysis techniques within two different (450 °C and 500 °C) substrate temperatures. The structural properties of ZnO:Cu thin films have been investigated by X-ray diffraction techniques. The X-ray diffraction spectra showed that ZnO:Cu thin films are polycrystalline with the hexagonal structure and show a good c-axis orientation perpendicular to the substrate. The most preferential orientation is along the (002) direction for all spray deposited ZnO:Cu films together with orientations in the (100) and (101) planes also being abundant. Some parameters of the films were calculated and correlated with the film thickness for two different substrate temperatures. The optical properties of ZnO:Cu thin films have been investigated by UV/VIS spectrometer and the band gap values were found to be ranging from 3.29 eV to 3.46 eV.     

Synthesis, morphology and optical properties of nanocomposite thin films based on polypyrrole-bromo-aluminium phthalocyanine

This paper is focused on the synthesis of nanocomposite Polypyrrole–Bromoaluminium phthalocyanine (PPy-BrAlPc). Morphology of prepared nano-compositethin films by electron beam evaporation technique have been well characterized by Field Emission-Scanning Electron Microscopy (FESEM). FESEM shows that the grain sizes are increased with increase in concentration of pyrrole. The optical properties of nanocomposite thin films have been investigated using a spectrophotometric measurement of absorbance in the wavelength range 300–800 nm. Absorption spectra of the films show B-band in the UV region followed by Q-band in the visible region. Moreover, the optical band gaps of the thin films are evaluated. It is found that the energy of the optical band gap increases as the concentration of Bromo-aluminium phthalocyanine increases.     

Influence of fluorine doping on structural, electrical and optical properties of spray pyrolysis ZnS films

ZnS films were deposited by spray pyrolysis on glass at 500 °C substrate temperature. In order to study the influence of fluorine on the properties of ZnS film, undoped and F-doped films were investigated using X-ray diffraction, scanning electron microscopy and optical transmittance spectroscopy. The absorption coefficient was measured and correlated with the photon energy to estimate the energy gap, which rises from 3.20 to 3.35 eV with increased F content. Carrier concentrations of our samples were determined from Hall effect measurements. It was found that the carrier concentration increases from 7.0 × 10¹² cm^− 3 to 8.0 × 10¹³ cm^− 3 with increasing F content from 0 to 6 wt.% in ZnS films.     

Study of structural,optical and electrical parameters of ZnSe powder and thin films

Nanocrystalline ZnSe powder and thin film forms have been synthesized via chemical bath deposition technique. The ZnSe thin films are deposited onto ultrasonically clean glass substrates in an aqueous alkaline medium using sodium selenosulphate as Se^2? ion source. The ZnSe powder and thin film are characterized by structural, optical and electrical properties. It is confirmed from X-ray diffraction study that cubic phase is present in ZnSe thin film form with (111) as preferred orientation and hexagonal phase is present in ZnSe powder form with (100) as preferred orientation. Optical absorption measurement indicates the existence of direct allowed optical transition with a wide energy gap and blue shift in the fundamental edge has been observed in both cases. The optical band gap of ZnSe powder is greater than the thin film. The electrical conductivity (both dark and photoconductivity) measurements are also carried out in different temperature range and variation in activation energy has been calculated.