Properties Of CdS Films Research Articles

Studies on the properties of cdS films deposited from pH-controlled growth solutions

In this work we have studied the properties of CdS films obtained by the chemical bath deposition technique. We studied the influence of pH control of the reaction solution on the structural and optical properties of chemically deposited CdS films. For this, we deposited two sets of CdS films on glass substrates using two different reaction solutions. The main difference between the solutions was that one included the use of a pH-10 NH4OH/NH4Cl controller solution or buffer, which produces a more uniform pH of the reaction solution during the film-growth process. Using each reaction solution, five CdS films were deposited at 80 °C, varying the deposition time from 15 to 120 minutes. The structural and optical properties of both sets of films were determined by X-ray diffraction and by absorption, transmission and reflection spectroscopy. The differences in the properties of the films were analyzed in terms of pH control.

CdS annealing treatments in various atmospheres and effects on performances of CdTe/CdS solar cells

In this work, a systematic research on CdS annealing treatments under various atmospheres had been done to understand their effects on CdS/CdTe solar cells. CdS films were prepared by a standard CBD method and annealed under various atmospheres, including Ar, Ar+H2, O2, Ar+S and Ar+CdCl2. Morphological, structural, optical and chemical properties were investigated using Atom force microscope (AFM), X-ray diffraction (XRD), UV–VIS spectroscopy and X-ray photoelectron spectroscopy (XPS). Annealing treatments enhanced modifications of morphology, structure and electrical properties of CdS films. AFM showed different surface morphologies and roughnesses of CdS films annealed under various atmospheres. XRD indicated the transition of CdS films from metastable cubic structure to stable hexagonal structure after annealing treatment, especially annealed in Ar+CdCl2. From XPS analysis, Fermi levels of CdS films shifted closer to conduction band after annealing under O2 and Ar+CdCl2, while the levels shifted away from conduction band under Ar+H2 and Ar+S. The relationships between those modifications by annealing treatments and effects on the performance of solar cells were discussed. Solar cell based on CdS annealed with Ar+CdCl2 had the best performance due to the high n-doping of CdS layer introduced by annealing process.

Effect of Sputtering Power on the Structural and Optical Properties of CdS Films

CdS thin films were prepared by radio frequency magnetron sputtering with different sputtering power. The effects of sputtering power on crystallinity, surface morphology and optical properties of the films were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-visible transmission spectra. The XRD measurement revealed that CdS films were polycrystalline and retained the mixed structure of hexagonal wurtzite and cubic phase. As the power increased, the H(002)/C(111) peak was more intense and sharper. This indicates that the CdS films are grown with the preferred orientation of the H(002)/C(111) plane at higher power, resulting in improvement in the film crystallinity. The morphology of all films was found to be continuous and dense. An increase in the power from 60 to 120 W, the optical band gap decreased from 3.44 to 2.42 eV.

Influence of substrates on the structural and optical properties of ammonia-free chemically deposited CdS films

CdS films were deposited on glass, indium-tin-oxide (ITO)/glass and Ti foil substrates by acidic chemical bath deposition technique. Effects of substrate type on the structural and optical properties of CdS films were studied. XRD patterns indicated that the structures of CdS films on ITO/glass and Ti foil were predominantly hexagonal and the structure of CdS films on glass was a mixed cubic and hexagonal. Atomic force microscope (AFM) analysis showed that the surface of CdS films on Ti foil substrate was rougher than that of CdS films on glass and ITO/glass substrates. The average transmittances of CdS films on glass and ITO/glass were about 71% and 75%, respectively. Diffuse reflection spectra also indicated the high transmittance of CdS films on Ti foil in the longer wavelength region, but PL and Raman spectra implied that more defects existed in CdS films on Ti foil substrate.

تأثير التشعيع على الخصائص البصرية لأغشية CdS المحضرة بطريقة التبخير الحراري في الفراغ

Effect of Gamma Radiation with different doses )0,1,5,10) Mrad was studied on the optical properties for CdS films of 1μm thickness prepared by thermal evaporation at pressure (10-6torr) on glass substrate. The optical properties of CdS films, absorbance, transmittance and reflectance have been studies in the wavelength range of (300-900)nm. The refractive index, extinction coefficient, absorption coefficient and dielectric constant were also studied as afunctionof photon energy and optical energy gap of allowed direct and forbidden transition. Radiation is change films colour to dark yellow and increase the value of absorption coefficient, extinction coefficient and dielectric onstant while occurs decreasing on the Reflectance, Refractive index and dielectric constant .

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.

Effects of Vapor CdCl<sub>2</sub> Treatment on the Properties of CdS Thin Films Prepared by R.F. Magnetron Sputtering

CdS films were prepared by R.F. magnetron sputtering method. The effects of vapor CdCl2 treatment on the properties of CdS films were studied. The vapor CdCl2 thermal treatment at different temperature was employed in a CSS device, using CdCl2 powder as evaporant. The structural and optical properties of CdS films were investigated by x-ray diffraction (XRD), PL spectra, and transmittance spectra, respectively. The results revealed that the CdS films had a structure of hexagonal wurtzite with a preferential orientation of the (002) plane. A better crystal quality and larger grain size, which are good for the solar cell application, were observed in the CdS samples annealed with CdCl2Subscript text.

Optical and Structural Properties of Nanocrystalline CdS Thin Films Grown by Chemical Bath Deposition

Nanocrystalline cadmium sulfide thin films are prepared using chemical bath deposition (CBD) technique in aqueous alkaline bath at 60 °C and their subsequent condensation on glass substrates. Effects of annealing on structural, morphological and optical properties are presented and discussed. The best annealing temperature for CBD grown CdS films is found to be 350 °C from optical properties. The optical and structural properties of CdS films are found to be sensitive to annealing temperature and are described in terms of XRD, SEM, transmission spectra and optical studies. The structural parameters such as crystallite size have been evaluated through XRD while SEM micrographs exhibit ordering of grains upon annealing. The transmission spectra shift towards higher wavelength upon annealing indicating increase in crystallinity. Annealing over 350 °C is found to degrade the external structure and optical properties of the film.

Optical Properties of Nanostructure in CdS at Different Condition Bath Deposition

In this work, CdS films were prepared by using chemical bath deposition. Many growth parameters have been considered in this work to specify the optimum condition, namely temperature of solution, pH, thiourea ion concentration and deposition time. Optical properties of CdS films are investigated and analyzed extensively with respect to growth conditions. Nanocrystalline CdS have been deposited, the band gap changes from 2.58 eV to 2.8 eV as compared to the bulk CdS band gap of 2.42 eV, as a result of quantum confinement.

On the mechanism of current-transport in Cu/CdS/SnO 2/In–Ga structures

The structural and optical properties of CdS films deposited by evaporation were investigated. X-ray diffraction study showed that CdS films were polycrystalline in nature with zinc-blende structure and a strong (1 1 1) texture. The study has been made on the behavior of Cu/n-CdS thin film junction on SnO 2 coated glass substrate grown using thermal evaporation method. The forward bias current–voltage ( I– V) characteristics of Cu/CdS/SnO 2/In–Ga structures have been investigated in the temperature range of 130–325 K. The semi-logarithmic ln I– V characteristics based on the Thermionic emission (TE) mechanism showed a decrease in the ideality factor ( n) and an increase in the zero-bias barrier height ( Φ Bo) with the increasing temperature. The values of n and Φ Bo change from 8.98 and 0.29 eV (at 130 K) to 3.42 and 0.72 eV (at 325 K), respectively. The conventional Richardson plot of the ln( I o/ T 2) vs q/ kT shows nonlinear behavior. The forward bias current I is found to be proportional to I o( T)exp( AV), where A is the slope of ln( I)– V plot and almost independent of the applied bias voltage and temperature, and I o( T) is relatively a weak function of temperature. These results indicate that the mechanism of charge transport in the SnO 2/CdS/Cu structure in the whole temperature range is performed by tunneling among interface states/traps or dislocations intersecting the space-charge region. In addition, voltage dependent values of resistance ( R i ) were obtained from forward and reverse bias I– V characteristics by using Ohm's law for each temperature level.

Vibrational and morphological properties of Sn-doped CdS films deposited by ultrasonic spray pyrolysis method

Cd 1− x Sn x S films ( x=0.0, 0.1 and 0.2) were prepared by the ultrasonic spray pyrolysis (USP) method on the glass substrate at 300 °C. Effect of Sn doping on the vibrational and morphological properties of CdS films has been investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), FT-IR and Raman spectroscopy. The SEM and AFM measurements showed that the surface morphology of the films was affected by the tin incorporation. The Raman (200–700 cm −1) and FT-IR (400–4000 cm −1) spectra of Cd 1− x Sn x S were recorded. The Raman spectrum for Cd 1− x Sn x S films is dominated by an intense band at 300 cm −1, assigned to the first-order longitudinal optic phonon and the second-order phonon peak 599 cm −1. The absorption peaks in the FT-IR spectra of Cd 1− x Sn x S located at 540–700 and 1004–1045 cm −1 can be assigned to the Cd–S and C–O stretching frequencies, respectively. Raman and FT-IR spectra shows decrease in the peak intensity with increasing Sn concentration.

Properties of CdS films deposited by the electron beam evaporation technique

Thin CdS films were electron beam evaporated. The CdS powder synthesized in the laboratory by a chemical method was used as source for the deposition of films. Clean glass substrates were used. The substrate temperature was varied in the range of 30–250 °C. X-ray diffraction studies indicated polycrystalline hexagonal structure. The band gap was 2.39 eV. The grain size was 25–35 nm and the surface roughness was 0.3–1.5 nm with increase of substrate temperature. Photoconductive cells fabricated with the doped and undoped films have exhibited high photosensitivity and high signal to noise ratio. The current voltage characteristics were linear.

CIGS solar cell with CdS buffer layer deposited by ammonia‐free process

AbstractWe have successfully fabricated high‐efficiency CuInGaSe2 (CIGS) solar cells with CdS film deposited by ammonia‐free process. The CdS films were formed on CIGS films by chemical bath deposition from an aqueous solution containing cadmium acetate and thioacetamide. The properties of CdS films deposited on soda lime glass were investigated by atomic force microscopy and optical transmission measurement. By optimizing the concentration of the solution used for the formation of CdS films and the thickness of i‐ZnO films used for solar cell production, high‐efficiency ammonia‐free cells were fabricated. The properties of the ammonia‐free cell fabricated by the optimized process were VOC = 0.695 V, JSC = 32.812 mA/cm2, FF = 0.755 and η = 17.22%. These values are comparable to those of the cells produced by the conventional process using ammonia. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Comparative study on structural and optical properties of CdS films fabricated by three different low-cost techniques

Highly crystalline and transparent cadmium sulphide films were fabricated at relatively low temperature by employing an inexpensive, simplified spray technique using perfume atomizer (generally used for cosmetics). The structural, surface morphological and optical properties of the films were studied and compared with that prepared by conventional spray pyrolysis using air as carrier gas and chemical bath deposition. The films deposited by the simplified spray have preferred orientation along (1 0 1) plane. The lattice parameters were calculated as a = 4.138 Å and c = 6.718 Å which are well agreed with that obtained from the other two techniques and also with the standard data. The optical transmittance in the visible range and the optical band gap were found as 85% and 2.43 eV, respectively. The structural and optical properties of the films fabricated by the simplified spray are found to be desirable for opto-electronic applications.

Annealing Effect on Structural, Electrical and Optical Properties of CdS Films Prepared by CBD Method

In this work CdS films were prepared by using chemical bath deposition, which is simple and inexpensive technique suitable for large deposition area. Annealing in air at different temperatures (300, 350, 400, 450 and 500 ℃) at constant time of 30 min, also for different times (15, 30, 45, 60 and 90 min) at constant temperature (300 ℃) is achieved. X-Ray analysis has confirmed the formation of cadmium oxide (CdO) with slight increase in grain size, shift towards lower scattering angle due to relaxation in the tensile strain for deposition films, and structure change from cubic and hexagonal to the hexagonal. From electrical properties, significant increase in electrical conductivity appeared in samples annealed at 300 ℃ for 60 min, and at 350 ℃ for 30 min.

EFFECTS OF EXCESSIVE REACTANTS ON THE PROPERTIES OF CADMIUM SULFIDE THIN FILMS PREPARED BY CHEMICAL BATH DEPOSITION

Cadmium sulfide nanoparticles were synthesized and grown on glass substrates by chemical bath deposition. The method involves the preparation of aqueous solutions containing cadmium chloride ( CdCl 2) and thiourea [ CS ( NH 2)2] as source materials for cadmium and sulfur components, respectively. Ammonium hydroxide ( NH 4 OH )–ammonium chloride ( NH 4 Cl ) solution was used as a complexing agent in this study. The hexagonal and cubic crystal structure of as-deposited CdS films, determined by X-ray diffraction (XRD), is shown. The effects of Cd : S ratio variation on the surface morphology and optical properties of CdS films are also reported. The UV-vis transmission spectrum and SEM micrographs indicated that the Cd : S ratio in the aqueous solution had an impact on the band gap as well as the crystallite size and packing density of the CdS particles due to the quantum confinement effect.

Investigations on microstructural and optical properties of CdS films fabricated by a low-cost, simplified spray technique using perfume atomizer for solar cell applications

Good quality CdS films were fabricated by employing a simplified spray pyrolysis technique using perfume atomizer. CdS films have been deposited from aqueous solutions of sulphur and cadmium, keeping the molar concentrations of S:Cd = 0.01:0.01, 0.02:0.02, 0.04:0.04 and 0.06:0.06 in the starting solutions. The structural studies reveal that the S:Cd concentration has a strong influence on the microstructural characteristics of the sprayed CdS films. It was found that there is a transition in the preferred orientation from (0 0 2) plane to (1 0 1) plane when S:Cd molar concentration increases. The SEM images depict that the films are uniform and homogeneous. All the films have high optical transmittance (>80%) in the visible range. The optical band gap values are found to be in the range of 2.46–2.52 eV. CdS films fabricated by this simple and economic spray technique without using any carrier gas are found to be good in structural and optical properties which are desirable for photovoltaic applications. Hence, this simplified version of spray technique can be considered as an economic alternative to conventional spray pyrolysis (using carrier gas), for the mass production of low-cost, large area CdS coatings for solar cell applications.

Effects of CdCl 2 treatment on the properties of CdS films prepared by r.f. magnetron sputtering

Effects of the thickness of CdCl 2 layer and the annealing on structural and optical properties of sputter-deposited CdS films were investigated. The annealing process of evaporated CdCl 2 was carried out by heating the sample in air at 350–500 °C for 20 min. As the thickness of the CdCl 2 increases, the (002) peak of CdS becomes weak and the other peaks of CdS increases. Especially, for 200 nm CdCl 2, the preferential orientation of the (002) plane disappears and the c-axis of the CdS film tends to orient parallel to the substrate. As the CdCl 2 layer is thicker, the grains are enlarged significantly. The improvement of optical properties of CdS films with thicker CdCl 2 layer might be successfully employed in achieving better conversion efficiencies in solar cells.

Preparation of CdS Thin Films through MOCVD Method, Using Cd-S Single-source Precursors

Numerous physical properties of CdS films notablydepend on their deposition methods and the particularconditions of preparation processes. They can be preparedby chemical, physical and electrochemical methods such asmolecular beam epitaxy (MBE); metal organic chemicalvapor deposition (MOCVD); close-spaced sublimation (CSS);chemical bath deposition (CBD); electro-deposition; succe-ssive ionic layer adsorption and reaction (SILAR); screenprinting; pulsed laser ablation; RF sputtering; and spraypyrolysis.

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)