Papers by Keyword: PbS Thin Film

Abstract: Thin film deposition of PbS is conveniently carried out by chemical reactions of lead acetate with thiourea at room temperature. Energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), selected area electron diffraction patterns (SAED), UV-Vis-NIR spectrophotometer, Scanning Electron Microscopy (SEM), Atomic force microscopy (AFM), Photoluminescence (PL) and Raman spectroscopy techniques are used for characterizing thin films. EDAX spectra shows that no impurity is present and XRD pattern indicates face centered cubic structure of PbS thin films. The average crystallite size obtained using XRD is about 15nm calculated using Scherrer’s formula and that determined from Hall-Williamson plot was found to be 18nm. SAED patterns indicate that the deposited PbS thin films are polycrystalline in nature. Blue shift due to quantum confinement was seen from the UV-Vis-NIR absorption spectra of thin film in comparison with bulk PbS. The Photoluminescence spectra obtained for thin film with different excitation sources shows sharp emission peaks at 395nm and its intensity of photoluminescence increases with increasing the excitation wavelength. Raman spectroscopy of deposited thin film was used to study the optical phonon modes at an excitation wavelength of 488nm using (Ar+) laser beam.

Abstract: Polycrystalline PbS thin films are being potentially used in different optical applications. Optimization of their optical response is always an area of interest. In the current paper, we report on the effect of deposition parameters such as concentration of reactants, dipping time and post deposition heat treatment on the grain size, structure, resistivity and optical response. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate was used for depositing PbS thin films on glass substrates. The deposition temperature was kept close to 100°C. Deposition of PbS films at such a high temperature and strong reactant concentrations has not been much emphasized in literature. The characterization of physical and optical properties was done by using XRD, SEM, DSC, dual beam spectrophotometer and two probe methods for resistivity measurement. Mean grain size and surface disorder increased with increasing reactant concentrations and dipping time. However, the effect was less prominent with increasing concentration of reactants than the deposition time. The structural features such as crystallite size, structure and film thickness directly correspond to photosensitivity and optical properties of thin films. Annealing affected the electronic properties considerably and lowered the band gap of material but did not cause any appreciable change in structure except smoothening of the grain boundaries to certain extent.

Abstract: In this study, we report on the structural parameters and texture development which occurred during deposition and annealing of PbS films and their effect on optical properties. The films under study were deposited on glass substrates through chemical bath method. The reactive substances used to obtain the PbS layers were lead accetae trihydrated, thiourea and hydrazine hydrate. The films were prepared with one molar bath concentration and for various deposition times. The data showed that as-prepared and annealed thin films are polycrystalline with cubic structure and predominantly textured along 100. Results showed that thinner films are more prone to post deposition heat treatments as compared to thicker ones. Deposition parameters and thermal treatment strongly influence the optical properties of PbS films.

Abstract: Lead sulfide (PbS) thin films were prepared by thermal evaporation onto glass substrates from PbS powder. The structure and DC electrical properties of evaporated PbS thin film sandwich structures with thicknesses (d) up to 600 nm have been investigated. X-ray diffraction studies showed that the films were crystalline, with a preferred orientation in the [111] direction. Capacitance measurements indicated that the films had a relative permittivity of 5.7. Room-temperature current density-voltage (J–V) characteristics revealed ohmic conduction below a transition voltage (Vt) and a power–law dependence with an exponent of ≈ 2 at higher voltages. This behaviour was interpreted in terms of space–charge limited conductivity controlled by an exponential distribution of traps below the conduction band edge. Further evidence for this conduction process was provided by a linear dependence of Vt upon d2. Analysis of the results yielded a room temperature electron concentration no of ≈ (3.9 – 5.4) x 109 m-3.