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Preetha K.C.,Kannur University | Preetha K.C.,Symphony | Remadevi T.L.,Kannur University | Remadevi T.L.,Pazhassi Raja Nss College
Materials Science in Semiconductor Processing | Year: 2013

Lead sulfide (PbS) thin films were prepared on soda lime glass substrates at room temperature by Chemical Bath Deposition (CBD) technique. This paper reports a comparative study of characteristic properties of as-prepared PbS thin films after thermal treatment through two different routes. Studies were carried out for as-prepared as well as rapidly and gradually annealed samples at 100, 200 and 300 °C. The characterizations of the films were carried out using X-ray diffraction, scanning electron microscopy and optical measurement techniques. The structural studies confirmed the polycrystalline nature and the cubic structure of the films. As-deposited films partly transformed to Pb 2O3 when gradually annealed to 300 °C. The presence of nano crystallites was revealed by structural and optical absorption measurements. The values of average crystallite size were found to be in the range 18-20 nm. The variation in the microstructure, thickness, grain size, micro strain and optical band gap on two types of annealing were compared and analyzed. Data showed that post deposition parameters and thermal treatment strongly influence the optical properties of PbS films. Optical band gap of the film gets modified remarkably on annealing. Direct band gap energy values for rapidly and gradually annealed samples varied in the range of 1.68-2.01 eV and 1.68-2.12 eV respectively. Thus we were succeeded in tailoring direct band gap energies by post deposition annealing method. © 2012 Elsevier Ltd. All rights reserved. Source


Preetha K.C.,Sree Narayana College | Remadevi T.L.,Pazhassi Raja Nss College
Materials Science in Semiconductor Processing | Year: 2015

Abstract Lead Selenide (PbSe) thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method to investigate the effect of hydrazine hydrate on film properties. The peak behavior of the X-ray diffractogram corroborates crystalline nature of PbSe thin films. The intensity of the major peaks attributable to PbSe improved at higher concentrations up to 5 ml HH and gets reduced for 7 ml HH. The average crystallite size is in the range 18.18-33.37 nm. The film surface of lower HH sample is composed of spherical grains which are arranged in a compact manner. On increasing HH some clusters appears on the surface of the film over a homogeneous background. The AFM micrographs show that the surfaces of the lead selenide thin films consist of dense distribution of nanoscale particles with a range of grain sizes. The roughness obtained is in the range 13.7-76.3 nm. Highly crystalline sample, 5HH exhibits very good topography. The direct band gap values are in the range 1.425-1.803 eV. Thus by varying HH we have been able to tune the band gaps over a wide range. The highly crystalline sample 5HH with least strain and excellent topography exhibits maximum conductivity. © 2015 Elsevier Ltd. Source


Remadevi T.L.,Kannur University | Remadevi T.L.,Pazhassi Raja Nss College | Preetha K.C.,Kannur University | Preetha K.C.,Sree Narayana College | Preetha K.C.,Symphony
Journal of Materials Science: Materials in Electronics | Year: 2012

Thin films of Lead sulphide (PbS) were grown on soda lime glass substrate by Successive Ionic Layer Adsorption and Reaction method from acidic, neutral and alkaline cationic precursor reaction bath by keeping the pH of the anionic precursor invariant. The structural and morphological aspects of the as prepared samples were investigated using XRD and SEM results. The as-prepared samples were polycrystalline with nanometer sized grains and identified as galena type cubic structure. The values of average crystallite size were found to be in the range 22-30 nm. The SEM micrographs show variations in morphology. Optical studies revealed the existence of both direct and indirect band gap with values in the range of 1.65-1.98 and 0.61-0.90 eV respectively. The room temperature conductivity of the PbS thin films were in the range 1.19 9 10-8-5.92 9 10-8 X cm-1. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and micro strain. The estimated lattice parameter, grain size, optical band gaps, solid state and electrical properties were correlated with pH of the cationic solution. In this work, we establish that the pH of the cationic precursor media has colossal effect on the structural, morphological, optoelectronic, solid-state and electrical properties of PbS thin films. © Springer Science+Business Media, LLC 2012. Source


Preetha K.C.,Kannur University | Preetha K.C.,Sree Narayana College | Remadevi T.L.,Kannur University | Remadevi T.L.,Pazhassi Raja Nss College
Physica B: Condensed Matter | Year: 2012

Doping of PbS thin films with different metal atoms produce considerable changes in structural and material properties that make them useful in the technology of thin film devices. The goal of this work is to study the effects of doping on the structural, morphological, optoelectronic and transport properties of PbS thin films as a function of Al 3 concentration. Thin films of pure and Al doped PbS nanoparticles are prepared on soda lime glass substrates by chemical bath deposition technique. The Al content in aqueous solution is varied from 0 to 20 mg. XRD analysis of the films revealed significant enhancement in crystallinity and crystallite size up to an optimum concentration of doping. Films are polycrystalline with crystallite size 19-32 nm, having face centered cubic structure. The optical band gap energy exhibits a decreasing trend and is shifted from 2.41 to 1.34 eV with increasing Al content. The room temperature conductivity of the as-deposited PbS films is in the range of 0.78×10 -8 to 0.67×10 -6( cm) -1 with a maximum for optimum Al content. The Al doped PbS thin film, which we synthesize with optimum Al concentration of 15 mg is found to be a most suitable material for solar control coating applications. © 2012 Elsevier B.V. Source


Preetha K.C.,Kannur University | Preetha K.C.,Sree Narayana College | Preetha K.C.,Symphony | Remadevi T.L.,Kannur University | Remadevi T.L.,Pazhassi Raja Nss College
Journal of Materials Science: Materials in Electronics | Year: 2013

An extensive study on the influence of metal ion sources on the properties of chemical bath deposited lead sulphide thin films is reported in this paper. Four different lead sources namely lead nitrate, lead acetate, lead chloride and lead sulphate in alkaline medium have been used for the synthesis along with thiourea as sulphur source. The influence of lead sources on structural, surface morphological optical and electrical properties is investigated for photovoltaic applications. According to X-ray diffraction studies, all the films are poly crystalline with face centered cubic structure. The average crystallite sizes are found to be in the range 13-24 nm. The SEM photographs showed diverse morphology. The optical band gap is found to be very sensitive to the metal sources used. The direct band gap energy values obtained are in the range of 1.862-2.609 eV. The electrical conductivity varies in the range 33.6 -7.62 × 10-9 (Ω cm)-1. Photosensitivity is closely linked to surface morphology. In this work, we established that the cationic precursor sources have significant role in physical properties of as-deposited PbS thin films. Samples prepared using nitrate as metal source are found to be most suitable to be used as solar control coating and the samples with lead acetate can be used as absorber layers for solar cell fabrication. © 2012 Springer Science+Business Media, LLC. Source

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