Room temperature electrosynthesis of ZnSe thin films

In the present study, we report the room temperature electrosynthesis of Zinc selenide (ZnSe) thin films on stainless steel (SS) and fluorine doped tin oxide (FTO) coated glass substrates. In addition, the influence of the substrate on the microstructural properties of ZnSe is plausibly explained. Voltammetric curves were recorded in order to characterize the electrochemical behaviour of Zn2+/SeO2 system. The as-deposited ZnSe thin films have been characterized for structural (X-ray diffraction (XRD)), surface morphological (scanning electron microscopy (SEM)), compositional (energy dispersive analysis by X-rays (EDAX)), surface topographical (atomic force microscopy (AFM)) and optical absorption analysis. Formation of cubic structure with preferential orientation along the (1 1 1) plane was confirmed from structural analysis. A significant observation seen from the SEM micrograph was the formation of porous layer on the FTO coated glass substrate. However, this is not seen in case of stainless steel substrate. Similar observation was predicted in case of AFM analysis for the films deposited on FTO. The optical band gap for ZnSe thin films was found to be 2.7 eV. © 2008 Elsevier B.V. All rights reserved

Growth and characterization of tin disulfide (SnS<inf>2</inf>) thin film deposited by successive ionic layer adsorption and reaction (SILAR) technique

Thin films of tin disulfide (SnS2) have been deposited by using low cost successive ionic layer adsorption and reaction (SILAR) technique. The deposition parameters such as SILAR cycles (60), immersion time (20 s), rinsing time (10 s) and deposition temperature (27 °C) were optimized to obtain good quality of films. Physical investigations were made to study the structural, optical and electrical properties. X-ray diffraction (XRD) patterns reveal that the deposited SnS2 thin films have hexagonal crystal structure. Energy dispersive X-ray analysis (EDAX) indicated elemental ratio close to those for tin disulfide (SnS(2.02)). Uniform deposition of the material over the entire glass substrate was revealed by scanning electron microscopy (SEM). Atomic force microscopy (AFM) showed the film is uniform and the substrate surface is well covered with small spherical grains merged in each other. A direct band gap of 2.22 eV was obtained. Photoluminescence (PL) showed two strong peaks corresponding to green and red emission. Ag/SnS2 junction showed Schottky diode like I-V characteristics. The barrier height calculated was 0.22 eV. Thermoelectric power (TEP) properties showed that tin disulfide exhibits n-type conductivity. © 2007 Elsevier B.V. All rights reserved

Electrical characterization of 100MeV heavy ion irradiated Au/p-Cu1.4S Schottky barrier diodes

Interface states play a vital role in Fermi-level pinning in Schottky barrier diodes. Here, we have modified the surface of copper sulfide by using 100MeV Au8+ swift heavy ions. On this modified surface, a Schottky diode was fabricated using gold metal. This leads to an interface with different 'interface states', affecting the charge transport and diode properties. I-V measurements showed that the current decreases with increase in ion fluence from 1011 to 1013ionscm-2, and barrier height increases while ideality factor decreases. These results are explained by taking into account the presence of free copper at the surface and grain boundaries of copper sulfide thin films and its diffusion into the matrix

Photoelectrochemical (PEC) studies on CdSe thin films electrodeposited from non-aqueous bath on different substrates

Thin films of CdSe were deposited by potentiostatic mode on different substrates such as stainless steel, titanium and fluorine tin-oxide (FTO) coated glass using non-aqueous bath. The preparative parameters were optimized to get good quality CdSe thin films. These films were characterized by X-ray diffraction (XRD), optical absorption and photoelectrochemical (PEC) techniques. XRD study revealed that the films were polycrystalline in nature with hexagonal phase. Optical absorption study showed that CdSe films were of direct band gap type semiconductor with a band gap energy of 1.8 eV. PEC study revealed that CdSe film deposited on FTO coated glass exhibited maximum values of fill factor (FF) and efficiency (η) as compared to the films deposited on stainless steel and titanium substrate. © Indian Academy of Sciences

Effect of annealing on structural and optical properties of zinc oxide thin film deposited by successive ionic layer adsorption and reaction technique

Zinc oxide thin films are grown by successive ionic layer adsorption and reaction technique at room temperature. The as-grown films were annealed at different temperatures, viz. 350, 400, 450, and 500 °C in air atmosphere for 2 h. Effect of annealing on the physical properties of ZnO thin films has been studied. XRD analysis reveals the polycrystalline nature for ZnO thin films with hexagonal phase. The films were highly oriented along (1 0 0) and (1 0 1) planes, an enhancement in these peaks is the significance of the post-deposition annealing treatment on ZnO thin films. The optical studies of the samples show that the energy band gap was decreased in accordance with the annealing temperature. The results of optical studies were strengthened by photoluminescence (PL) studies. © 2008 Elsevier B.V. All rights reserved

Growth and characterization of CdZn(S<inf>1-x</inf>Se<inf>x</inf>)<inf>2</inf> alloy film deposited by solution growth technique

The n-CdZn(S1-xSex)2 thin films have been deposited by solution growth technique. The various deposition parameters such as pH of solution (10.5), time, concentration of ions and temperature have been optimized. In order to achieve uniform films, triethanolamine (TEA) has been used. The as deposited films have been annealed in rapid thermal annealing (RTA) system at 250 °C in air for 5 min. The surface morphology, compositional ratio, structural properties have been studied by SEM, EDAX and XRD techniques, respectively. The XRD study shows that all the films are of polycrystalline in nature and exhibits the hexagonal and cubic structure for the composition x = 0.0-0.7 and x > 0.7, respectively. For hexagonal structure, the lattice constants 'a' varies from 4.13 Å to 4.04 Å and 'c' = 6.615 Å to 6.514 Å and for cubic structure 'a' varies from 5.629 Å to 5.598 Å. The absorption coefficient 'α' varies in the range 2 × 104 cm-1 to 17 × 104 cm-1. Band gap values were calculated from the transmittance spectra, which showed a non-linear variation with respect to composition 'x'. © 2006 Elsevier B.V. All rights reserved

A comparative study of the physical properties of CdS, Bi<inf>2</inf>S<inf>3</inf> and composite CdS-Bi<inf>2</inf>S<inf>3</inf> thin films for photosensor application

Thin films of CdS, Bi2S3 and composite CdS-Bi2S3 have been deposited using modified chemical bath deposition (M-CBD) technique. The various preparative parameters were optimized to obtain good quality thin films. The as-deposited films of CdS, Bi2S3 and composite were annealed in Ar gas at 573 K for 1 h. A comparative study was made for as-deposited and annealed CdS, Bi2S3 and composite thin films. Annealing showed no change in crystal structure of these as-deposited films. However, an enhancement in grain size was observed by AFM studies. In addition change in band gap with annealing was seen. A study of spectral response, photosensitivity showed that the films can be used as a photosensor. © 2007 Elsevier B.V. All rights reserved

Modifications of structural, optical and electrical properties of nanocrystalline bismuth sulphide by using swift heavy ions

Modified chemical bath deposited (MCBD) bismuth sulphide (Bi2S3) thin films' structural, optical and electrical properties are engineered separately by annealing in air for 1 h at 300 °C and irradiating with 100 MeV Au swift heavy ions (SHI) at 5 × 1012 ions/cm2 fluence. It is observed that the band gap of the films gets red shifted after annealing and irradiation from pristine (as deposited) films. In addition, there is an increase in the grain size of the films due to both annealing and irradiation, leading to the decrease in resistivity and increase in thermoemf of the films. These results were explained in the light of thermal spike model. © 2008 Elsevier B.V. All rights reserved

Effect of high electronic energy loss of 100 MeV gold heavy ions in copper chalcogenides (CuX, X = S, Se) at nanoscale: Opto-electronic properties study

The copper chalcogenide (CuX, X = S, Se) thin films have been irradiated with 100 MeV gold swift heavy ions (SHI) at 1011 and 1012 ions/cm2 fluences. The irradiation effects were probed by characterizing physical properties such as XRD, AFM, optical band gap and electrical resistivity of copper chalcogenide thin films. The increase in irradiation fluence increases the particle size, electrical conductivity and PL intensity of the materials, and the optical band edges were red shifted. The results are explained by quantifying electronic energy loss of ions in both the materials. © 2009 Elsevier B.V. All rights reserved