Structure Of CdS Thin Films Research Articles

Structural and optical characterization of sprayed Mg and Ni co-doped CdS thin films for photovoltaic applications

In the present work, Mg and Ni co-doped CdS thin films are grown on glass substrates at a temperature of 400 °C through spray pyrolysis. The influence of Mg-doping on structural, morphological and optical properties of CdS:Ni thin films are examined. Mg level is changed from 0 % to 7 % for CdS: Ni samples just as Ni concentration is fixed 2 % for all CdS thin films. It is observed from the X-ray diffraction spectra that all the samples exhibit hexagonal structure of CdS thin films. The scanning electron microscopy (SEM) images showed a dense surface structure composed of crystallites whose average size increase with increasing the Mg doping. The optical transmission curves demonstrate that CdS:Ni thin films exhibit a best optical transparency in the visible range for 1 % Mg content compared to other specimens. The energy of the optical band gap tends to decrease from 2.46 to 2.40 eV with increasing Mg concentration in CdS: Ni.

Effects of different substrates and CdCl2 treatment on the properties of CdS thin films deposited by magnetron sputtering

CdS films were deposited on corning 9059 glass, FTO, ITO and AZO substrates by r.f. magnetron sputtering, and annealed at 380 ℃ in CdCl2+ dry air. Effects of different types of substrate and thermal annealing on the morphology, structure and optical properties were investigated. Field emission scanning electron microscope shows: the morphology of as-deposited and annealed CdS thin films on different substrates is different, grain size and surface roughness increase significantly with annealing. XRD diffraction patterns show: the structure of as-deposited and annealed CdS thin films on different substrates are mixed phase structure of hexagonal and cubic phases, there is a preferential orientation of the crystallits with the hexagonal (002) and cubic (111) peak for as-deposited and annealed CdS films on corning 9059 glass, FTO, and AZO substrates, for as-deposited CdS film on ITO substrate there is no preferentially oriented diffraction peaks, but has highly oriented with hexagonal (002) or cubic (111) peak after annealing; UV-Vis spectrophotometer spectrum analysis shows: the average transmittance in visible spectrum of CdS thin films deposited on AZO, FTO, ITO and Corning 7059 glass substrates in turn decreases, annealing increases the corresponding substrate of CdS films in visible light transmittance, reduces the optical absorption coefficient; annealing significantly increases the band gap of CdS films on different substrates. Analysis reveals that the performance comes from the result of different types of substrate and annealing process for morphology and structure of CdS thin films, and the band tail states changes, due to variation of doping concentration.

Study of Transmittance of CdS Thin Films Prepared by Spray Pyrolysis

Cadmium chloride and thiourea were used as raw materials to synthesize precursor solution, and CdS thin films were prepared on glass substrates by the home-made spray pyrolysis thin-film preparation device.Affects of preparation parameters, for example, the substrate temperature and fog particle velocity on the structure of CdS thin films were emphatically studied in the paper. The results showed that the optimum conditions for preparation of CdS thin films are as follows: the substrate temperature 350 °C, the gas flow rate 4L/min, and the annealing temperature 400 °C. Under the optimum conditions and argon as the carrier gas, with a spray time of 32s, a 1.9μm thickness CdS film which had a (002) plane grain size of 32.3nm was obtained. And the transmittance of the film was above 70% at the wavelength range of from 500nm to 850nm.

Humidity Sensing Properties of CdS Nanoparticles Synthesized by Chemical Bath Deposition Method

Thin films of CdS nanoparticles were synthesized by the chemical bath deposition (CBD) technique to investigate humidity response characteristics. The morphology and the crystal structure of CdS thin films were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The quartz crystal microbalance (QCM) technique was used to measure the water vapor adsorption and desorption rates of CdS thin films. The dynamic Langmuir model was used to analyze the kinetics of the moisture adsorption and desorption process under relative humidity (RH) between 17 and 85% RH. Our results indicate that CdS thin films have a great affinity to humidity at room temperature.

Effects of cadmium salts on the structure, morphology and optical properties of acidic chemical bath deposited CdS thin films

CdS thin films were deposited from different cadmium salts by using acidic chemical bath deposition (CBD) process. Quality characterizations were performed using different methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). The crystal quality of CdS thin films was improved after CdCl 2 thermal annealing at 380 °C. A compact structure of CdS thin films can be obtained by using CdCl 2 in comparison with the other cadmium salts. Although a Cd/S molar ratio of ∼1 was used in our experiments, strong PL signals confirmed the high quality of CdS thin films.

Modelling of the structure of CdS thin films

The structure of CdS thin films produced by chemical bath deposition for window layers for photovoltaic devices has been investigated using the techniques of standard θ–2θ X-ray diffraction (XRD) and glancing angle XRD (GAXRD). The relative peak intensities observed in the diffraction patterns were consistent neither with a cubic nor a hexagonal microstructure. By employing both diffraction geometries on the same sample it was established that the CdS layers were un-textured, thus a structure different from either the cubic or hexagonal modifications was inferred. In order to elucidate the crystalline structure of the material a Rietveld analysis program was employed, together with a special program written to generate appropriate input parameter files. It was found that a good match between experimental and simulated patterns could be obtained by postulating a polytype CdS structure, consisting of nearly random stacking sequences of the hexagonal planes that form the basis for both the cubic (zinc-blende) and hexagonal (wurzite) modifications. The GAXRD results indicate that little structural change occurs in the polytype CdS upon annealing in air, despite a pronounced colour change. The structural difference between films deposited under different conditions is much more pronounced than that between as-deposited and annealed material. The results are discussed with reference to investigations by other authors of CdS thin films and of CdS nanoparticles using the techniques of transmission electron microscopy and/or X-ray or electron diffraction.

The structure study of thin semiconductor and dielectric films by diffraction of synchrotron radiation

The structure of semiconductor and dielectric thin (100–300 nm) films was studied by diffraction of synchrotron radiation. The diffraction experiments were performed at both the station “Anomalous scattering” of the storage ring synchrotron facility VEPP-3 and DRON-4 diffractometer. The structure of CdS thin films grown on fused silica, single Si(100) and InP(100) substrates was investigated. The structure of Cu 2S thin films grown on fused silica, single Si(100) substrates and CdS/Si(100)-heterostructure was studied. The structure study was performed on Si 3N 4 films grown on GaAs(100) substrates. The structure of thin BN layers grown on single Si(100) substrates was studied. It was established that structural parameters of above-mentioned thin films coincide on the parameters of JCPDS International Centre for Diffraction Data.

Changes in the electrical properties and surface structure of CdS thin films due to thermal treatment: N P Zatovskaya and V V Serdyuk, Izv VUZ Fiz, No 7, 1970, 122–124 ( in Russian).

Changes in the electrical properties and surface structure of CdS thin films due to thermal treatment: N P Zatovskaya and V V Serdyuk, Izv VUZ Fiz, No 7, 1970, 122–124 ( in Russian).