Properties Of CdS Thin Films Research Articles

Studying the Optical Properties of CdS Thin Films Prepared by Thermal Vacuum Evaporation Technique with a Different Thickness

CdS thin films with a different thickness have been prepared on glass substrates by using the thermal vacuum evaporation technique at substrate temperature of 150oC. The optical characteristics of the prepared thin films have been investigated by UV-VIS spectrophotometer in the wavelength range (300-1100 nm) . The films have a direct allow electronic transitions and the optical absorption are shifted to the low energies by increasing the thickness . Also the optical energy gap (Eg) has decreased from 2.47 eV to 2.22 eV by increasing the thickness value. The extinction coefficient (k) , refractive index (n) and the real and imaginary dielectric constants (ε1 , ε2 ) are investigated. All of these constants increased with the increases in thickness and shifted to the low energies

Influence of Annealing Temperature on the Electrical and Optical Properties of CdS Thin Films

Influence of Annealing Temperature on the Electrical and Optical Properties of CdS Thin Films

Effect of EDTA concentration on the physical and optical properties of Cds thin films

AbstractApplication of ethylenediamine tetraacetic acid (EDTA) in the chemical bath solution to enhance the physical and optical properties of chemical bath deposited CdS film was realised. The observed beneficial effect on the crystallisation of CdS crystallites in the bath solution followed by deposition on glass substrates reduces the amorphousity and enhances the crystallinity of the film. The optical transparency of the film attains a maximum of 80% over the wavelength range of 650–1100 nm for the film deposited from EDTA‐added solution having the concentration of 0.006 mol/L. Also, the observed intensity of the characteristic photoluminescence emission was found to be dependent on the concentration of EDTA in the bath solution. © 2011 Canadian Society for Chemical Engineering

Preparation and Properties of CdS Thin Films Deposited by Chemical Bath Deposition

CdS thin films deposited on glass substrate are prepared by chemical bath deposition using the reaction between CdSO4 and CS (NH2)2. The composition, surface morphology and structural properties of as-deposited and annealed CdS thin films were studied using scanning electron microscopy (SEM), X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The results indicate that the dense, homogeneous polycrystalline CdS thin films with smooth surface can be obtained by chemical bath deposition. The CdS thin films have cubic structure and the ratio of S and Cd is 1:1 in CdS thin films. Optical properties of CdS films were measured with ultraviolet-visible spectrophotometer. The optical band gap energy (Eg) of film sample was found to be 2.31 eV.

CdS Thin Films Deposited by CBD Method on Glass

CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron microscope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X-ray diffraction results showed the film structure was a mixture of two phases: hexagonal and cubic, and it was very important to controll deposition time to the film's crystal phase. All films in depth of approximate 100 nm existed above 65% transmittance, the absorption edge became “red-shift" with temperature rising. At 60 and 70 °C, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90 °C, the energy band gap was less than 2.42 eV and increased little when the time changed from 10 min to 15 min at 80 °C.

Hydrogenation effect on structural, electrical and optical properties of CdS thin films for solar cell

Adsorption effects would be expected to be of considerable importance with thin films because of the changes in electron location accompanying adsorption. The effects of hydrogenation on structural, optical and electrical properties of the CdS thin films have been reported. GIXRD patterns shows that films have polycrystalline nature with a hexagonal structure. The optical band gap increased after hydrogenation of the film. The variation of conductivity of CdS films have been investigated depending upon the applied voltage at room temperature. The resistivity increased after hydrogenation of the films. Hydrogenated thin films can be used in solar cells because hydrogen plays an important role to modify the physical properties.

Effects of the Thermal Annealing with CdCl<sub>2</sub> on the Optical Properties of CdS Thin Films Grown by Radio-Frequency Planar Magnetron Sputtering

We present in this work some results concerning the effects of the thermal annealing withCdCl2on the optical properties ofCdSthin films grown by radio-frequency planar magnetron sputtering technique, under optimized growth parameters: gas pressure, atmosphere, substrate temperature, power of plasma, etc. An improvement of the optical properties has been observed, mainly the presence of radiative emission (luminescence) at room temperature. This fact allowed us to carry out a deep study of the photoluminescence (PL) properties of theCdSfilms, in the range of temperature 10≤ T ≤ 300 K. Radiative emission at the high energy side has been observed and related to exitonic processes. Temperature quenching experiments gave rise to the calculation of the activation energies for each one of the radiative emissions (PLbands).

Effects of the Surface Roughness on Optical Properties of CdS Thin Films

The effects of surface roughness on the optical properties of CdS thin film was investigated using RMS roughness measurements. CdS thin films for a window layer of the CdTe thin film solar cell were grown on ITO glass by a chemical bath deposition method with varying thiourea (CS(NH2)2) mole concentration. The surface roughness of the CdS thin film was measured by Atomic Force Microscopy (AFM). After obtaining the correlation factor between the RMS roughness and the difference in the diffused transmittance and the spectral transmittance by using the integrating sphere, we investigated the effect of surface morphology on the transmittance in all CdS thin films. It is obtained that the higher RMS value the specimen has, the more difference between the diffused transmittance and the spectral transmittance is measured. Moreover, the difference is evident at the long wavelength region.

Effect of Fe-ion implantation doping on structural and optical properties of CdS thin films

We report on effects of Fe implantation doping-induced changes in structural, optical, morphological, and vibrational properties of cadmium sulfide thin films. Films were implanted with 90 keV Fe+ ions at room temperature for a wide range of fluences from 0.1×1016 to 3.6×1016 ions cm−2 (corresponding to 0.38–12.03 at.% of Fe). Glancing angle X-ray diffraction analysis revealed that the implanted Fe atoms tend to supersaturate by occupying the substitutional cationic sites rather than forming metallic clusters or secondary phase precipitates. In addition, Fe doping does not lead to any structural phase transformation although it induces structural disorder and lattice contraction. Optical absorption studies show a reduction in the optical band gap from 2.39 to 2.17 eV with increasing Fe concentration. This is attributed to disorder-induced band tailing in semiconductors and ion-beam-induced grain growth. The strain associated with a lattice contraction is deduced from micro-Raman scattering measurements and is found that size and shape fluctuations of grains, at higher fluences, give rise to inhomogeneity in strain.

Study of some structural , optical , Electrical Properties of CdS thin films deposited by chemical Spray Pyrolysis Method

In this research we prepared CdS thin films by Spray pyrolysis method on a glass substrates and we study its structural , optical , electrical properties .The result of (X-Ray ) diffraction showed that all thin films have a polycrystalline structure , The relation of the transmission as a function of wavelength for the CdS films had been studied , The investigated of direct energy gap of the CdS its value is (2.83 eV). In Hall effect measurement of the CdS we find the charge carriers is p – type and Hall coefficient 1157.33(cm3/c) ,Hall mobility 6.77(cm2/v.s)

Study of some structural , optical , Electrical Properties of CdS thin films deposited by chemical Spray Pyrolysis Method

In this research we prepared CdS thin films by Spray pyrolysis method on a glass substrates and we study its structural , optical , electrical properties .The result of (X-Ray ) diffraction showed that all thin films have a polycrystalline structure , The relation of the transmission as a function of wavelength for the CdS films had been studied , The investigated of direct energy gap of the CdS its value is (2.83 eV). In Hall effect measurement of the CdS we find the charge carriers is p – type and Hall coefficient 1157.33(cm3/c) ,Hall mobility 6.77(cm2/v.s)

Modifications in structural and optical properties of Mn-ion implanted CdS thin films

In this paper, we report on modifications in structural and optical properties of CdS thin films due to 190 keV Mn-ion implantation at 573 K. Mn-ion implantation induces disorder in the lattice, but does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. The optical band gap was found to decrease with increasing ion fluence. This is explained on the basis of band tailing due to the creation of localized energy states generated by structural disorder. Enhancement in the Raman scattering intensity has been attributed to the enhancement in the surface roughness due to increasing ion fluence. Mn-doped samples exhibit a new band in their photoluminescence spectra at 2.22 eV, which originates from the d– d ( 4 T 1 → 6 A 1) transition of tetrahedrally coordinated Mn 2+ ions.

Effect of oxygen on CdS polycrystalline thin films prepared in ambient of Ar and O2 by close spaced sublimation technology

In this paper，CdS polycrystalline thin films were prepared with the close-spaced sublimation （CSS） technology. In the deposition process，a controlled ambient of Ar and O2 mixture was used. The effect of oxygen on the microstructure，composition，morphology as well as optical and electrical properties of CdS thin films were studied systemically by XRD，XPS，AFM，UV-VIS and four-probe array method. The results showed that the CSS-grown CdS thin film has the hexagonal structure with crystallite size about 40 nm and the composition of them were rich in S. The impurity oxygen atoms mixed into CdS thin films and partly formed CdO，and with the increase of O2 concentration the chemical composition tinds more closely to the ideal stoichiometric proportion of CdO，the optical gap of thin films broadened and the ratio of photoconductivity to darkconductivity increased. Fortunately these effects are benefitial to CdS thin films for the photovoltaic application as a window layer.Additionally，it view of CdS/CdTe interface，we investigated the influence of oxygen on the cross-section morphology of CdS/CdTe thin films and the spectral response （SR） of the device. Then the results indicated that with the increase of O2 concentration in deposition ambient，the interdiffusion between CdS and CdTe decreased，and the SR of device in the range from 500 nm to 600 nm increased.We believe that the oxygen in CSS-grown CdS thin films plays a very important role in two aspects，firstly in improving the quality of CdS thin films for photovoltaic application，secondly in optimizing the CdS/CdTe interfacial properties in the CdTe solar cells.

Structural, optical and magnetic properties of Cd1−xCoxS thin films prepared by spray pyrolysis

Abstract Structural, optical and magnetic properties of CdS thin films with the addition of Co prepared by (i) spray pyrolysis of Cd1−xCoxS (x⩽0.10) thin films (Type 1) and (ii) Co diffusion doped CdS films (Type 2) were investigated. The undoped film has a hexagonal structure with a strong (1 1 2) preferred orientation. As the Co concentration in CdS is increased, the preferred orientation changes from (1 1 2) to (0 0 2) direction. X-ray photoelectron spectroscopy (XPS) analysis shows that Co atoms on the surface of films are found to be bounded either to S atoms or O atoms. Although most of the bindings of Co atoms include Co–O bondings, some of them replace the Cd atoms by making chemical bounds with S atoms. The transmittance spectra indicate the four characteristic absorption maxima at the wavelengths of 680, 685, 729 and 744 nm, which were not observed for the undoped CdS film. Band gap energy Eg decreases from 2.43 to 2.37 eV with increasing Co content from x=0 to 0.10. The Co-doped Cd1−xCoxS films grown by spray pyrolysis (Type 1) didnot show any sign of ferromagnetic behavior. However, the Co diffused CdS films (Type 2) have clear ferromagnetic loops.

Characterization of chemical bath deposited CdS thin films doped with methylene blue and Er3+

The optical, electrical, and structural properties of CdS thin films grown by chemical bath deposition and simultaneously doped with methylene blue (MB) and Er3+ were studied. Doping was achieved by adding a constant volume of an MB aqueous solution to the chemical bath while the relative volume (VR) of the Er aqueous solution varied within the range 0–10% of the total growing solution. X-ray diffractograms displayed the zincblende crystalline structure for all the CdS samples, with a remarked preferred orientation along the (111) direction. The interplanar distance among the (111) planes decreased for low doping leves of Er3+, while for high doping concentrations such distance increased to saturation. Measurements on the carriers density indicated that the CdS thin films doped with Er3+ at 6% VR presented the maximum value. In addition, the band gap energy (Eg) resulted higher for CdS:MB films with low Er3+ doping levels than for undoped films; however, Eg decreased until stabilization for increasing Er3+ concentrations.

A variable electron beam and its irradiation effect on optical and electrical properties of CdS thin films

A low energy electron accelerator has been constructed and tested. The electron beam can operate in low energy mode (100 eV to 10 keV) having a beam diameter of 8–10 mm. Thin films of CdS having thickness of 100 nm deposited on ITO-coated glass substrate by thermal evaporation method have been irradiated by electron beam in the above instrument. The I–V characteristic is found to be nonlinear before electron irradiation and linear after electron irradiation. The TEP measurement confirms the n-type nature of the material. The TEP and I–V measurements also confirm the modification of ITO/CdS interface with electron irradiation.

Swift heavy ion beam irradiation induced modifications in structural, morphological and optical properties of CdS thin films

The effect of 100MeV Ag+7 ion irradiation on the properties of thermally evaporated CdS thin films has been investigated. The structure of the films studied is polycrystalline with a mixture of dominant hexagonal and few traces of cubic phases. A shift in the peak position due to irradiation was observed and is discussed on the basis of change in the residual stress. Annihilation of microcracks due to irradiation induced grain growth has been observed from the SEM micrographs at lower ion fluences. The optical transmittance and absorption spectra revealed a shift in the fundamental absorption edge and hence variations in the optical band gap. The band gap energy has been estimated for as-deposited and irradiated films and is found to decreases upon irradiation. A significant increase of refractive index has been observed after irradiation.

Physical properties of CdS thin films grown by pulsed laser ablation on conducting substrates: effect of the thermal treatment

AbstractStructural, morphological and optical properties of CdS films, deposited by the pulsed laser ablation technique on SnO2:F/glass substrates, were studied as a function of time deposition. Up to our knowledge the properties of these films grown onto conducting polycrystalline substrates have not been reported before. The photoluminescence measurements showed the existence of an exciton peak at room temperature, as an indication of good crystalline quality of the layers. A thermal treatment was applied to the samples in a 100 mT Ar atmosphere at 400 °C for 30 min after the deposition of a CdCl2 layer on them. Films characterization was carried out through X‐ray diffraction, photoluminescence and atomic force microscopy measurements. The structural, optical and morphological properties as a function of growth parameters are presented and discussed. Thermal treatment makes uniform the grain size in the samples, with a tendency to increase the grain size average. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of annealing on structural, optical and electrical properties of CdS thin films grown by ILGAR

CdS thin films were deposited by ILGAR(ion lay gas reaction) method. The effect of annealing temperature under N2 atmosphere on the structural, chemical, topographical development and optical and electrical properties of CdS thin films was investigated by XRD, SEM, XPS, UV-VIS and two-probe technique. It is found that the cubicphase of as-deposited CdS film transforms to hexagonal phase with a perfected orientation along (002) plane at 300 °C. The band gap decreases with increasing annealing temperature until 300 °C, which is consistent with the grain growth. The fall of dark and light resistivitiy is obvious with increasing annealing temperature, corresponding to the continuous grain growth and deviation of stoichiometry at higher temperature. The smooth and uniform surface of as-deposited films becomes rougher through thermal treatment, which is related to grain growth and sublimation of CdS at a higher annealing temperature.

Influence of the fluorine doping on the optical properties of CdS thin films for photovoltaic applications

The performance of CdTe/CdS thin film solar cells is strongly dependent on the properties of the CdS layer. In particular the electrical properties of the heterojunction between n-type CdS and p-type CdTe are influenced by the recombination activity at the grain boundaries. It is found that introducing fluorine in the sputtering chamber during CdS growth, the solar cell efficiency is improved. In order to study the influence of fluorine on the optical properties of CdS, undoped and F-doped thin films are investigated by cathodoluminescence and spectroscopic ellipsometry. Cathodoluminescence analyses reveal an improvement of the luminescence efficiency of the F-doped material, with respect to the undoped one, through the observed increase of the intensity of the near band edge emission at about 2.42 eV, accompanied by a blue shift of the center of the band. An analogous improvement of the optical response is confirmed by the ellipsometry results, showing an increase of the optical bandgap and a steeper absorption edge for the F-doped films. A model based on the reaction of the incorporated fluorine with the interstitial Cd atoms is presented, in order to explain the differences in the luminescence behavior between the undoped and F-doped samples and the observed passivation of the grain boundaries. Spectroellipsometric measurements reveal that the presence of fluorine reduces the growth rate of CdS and increases the bandgap and reduces the refraction and extinction indexes.