K.D. Patel

Characterization of SnSePb0.1 Thin Films Deposited by Flash Evaporation Technique

Tin Selenide compounds have attracted considerable attention because of their important properties useful for optoelectronics, holographic recording systems, electronic switching and infrared production and detection. Moreover, SnSe is a semiconductor with a band gap of about 1 eV that makes it potential candidate for solar cell material. Further, the optoelectronic properties of SnSe can be modified using doping of lead, copper etc. In this context, we report here results of the preparation and characterization of flash evaporated lead doped SnSe thin films. Thin films of SnSePb0.1 having thickness of 100nm and 500nm were deposited on to chemically cleaned glass substrates. The chemical composition of the deposited SnSePb0.1thin films has been evaluated using EDAX technique. The structure of SnSePb0.1was studied using low angle XRD and it shows that the deposited films are polycrystalline in nature having orthorhombic structure. Various lattice parameters along with micro strain for both 100nm and 500nm thin films have been evaluated. Electrical transport properties have been also investigated using high temperature Hall Effect measurement in the temperature range 300 400K. The decrease in the resistivity of deposited films with increasing temperature confirms the semiconducting behavior of SnSePb0.1 thin films.

Optical Absorption Study of Molybdenum Diselenide and Polyaniline and their Use in Hybrid Solar Cells

The optical characterization of Molybdenum diselenide (MoSe2) and polyaniline (PANI) has been carried in the wavelength range 200 nm to 2500 nm. The detailed analysis of the optical properties has been carried out only for a range 200 nm to 800 nm from which the indirect band gap around 1.42 eV for MoSe2 and 1 eV and 2.5 eV for PANI was evaluated. It was interesting to note that π π* transitions lead to two distinct orders of energy gaps. The hybrid cells were fabricated using a photosensitive interface between MoSe2 and PANI. Various parameters of these heterostructure hybrid cells have been evaluated and it was found that the photoconversion efficiency was around 1%. Using the solar cell characteristics, the presence of trapping centers at the n-MoSe2/ p-PANI interface has been confirmed.

Structural and Thermoelectric Properties of Tungsten Diselenide Crystals

Crystals of Tungsten diselenide (WSe2) have been grown by direct vapour transport (DVT) technique using micro processor controlled dual zone horizontal furnace. The chemical composition and structure of grown crystals were confirmed using energy dispersive analysis of X‐ray (EDAX) and X‐ray diffraction (XRD). In the present investigation thermoelectric power measurements (TEP) have been carried out on the grown crystals. Different electrical transport parameters of semiconductors have been determined and discussed in the paper.Crystals of Tungsten diselenide (WSe2) have been grown by direct vapour transport (DVT) technique using micro processor controlled dual zone horizontal furnace. The chemical composition and structure of grown crystals were confirmed using energy dispersive analysis of X‐ray (EDAX) and X‐ray diffraction (XRD). In the present investigation thermoelectric power measurements (TEP) have been carried out on the grown crystals. Different electrical transport parameters of semiconductors have been determined and discussed in the paper.

Retrieval of surface reflectance from Resourcesat-2 AWiFS, LISS-3, and LISS-4 data using SACRS2 scheme

Satellite based multispectral imagery contains various quantitative information related to surface and atmosphere. To extract the accurate information about surface, we need to correct atmospheric influence which is introduced by the atmosphere. Atmospheric correction of multispectral satellite imagery is an important prerequisite to derive geophysical parameters from satellite data. In this study surface reflectance is retrieved using the Scheme for Atmospheric Correction of Resourcesat-2 (SACRS2). The SACRS2 is physics based atmospheric correction scheme developed at Space Applications Centre (SAC), ISRO based on radiative transfer model 6SV (The Second Simulation of the Satellite Signal in the Solar Spectrum vector version). SACRS2 method is easily applicable for atmospheric correction of multispectral data. A detail analysis has been carried out to retrieve surface reflectance from Resourcesat-2 AWiFS, LISS-3 and LISS-4 data using SACRS2 method. The retrieved surface reflectance from SACRS2 for AWiFS, LISS-3 and LISS-4 have been compared with in-situ measurements. The comparison showed a good match of reflectance derived by SACRS2 scheme with the in-situ measurements.

MoSe2/Polypyrrole Solar Cell

MoS possesses a band gap around 1.4 eV which is nearly to maxima of solar radiations. The investigations on this kind MoSbased photovoltaic cells having the rectifying interface with polypyrrole. It was observed that MoS/polypyrrole structure exhibits a photovoltaic behaviour. The photoconversion efficiency and fill factor of above cell is calculated, the maximum photoconversion efficiency is 0.089 and fill factor is 0.5.

Preparation and Characterization of N-CdS Thin Films and its Schottky Barrier

Cadmium sulphide (CdS), a member of group II-VI semiconductors is one of the promising materials from its applications point of view. The present investigations are about the preparation, structural and optical characterization of CdS thin films and their use as Schottky diode with Aluminum. Thin films of CdS having thickness around 700nm have been deposited by thermal evaporation. The chemical composition of the deposited CdS thin films has been made using EDAX technique. The structural characterization of this films was carried out using XRD. The structure of CdS after the deposition was found to be Cubic. Also, the lattice parameters were evaluated from the XRD data. From TEM of CdS thin films, the polycrystalline nature was confirmed. Optical characterization has been carried out using UV-VIS-IR spectroscopy. The direct as well as indirect band gaps obtained are 1.64eV and 1.48eV respectively. Schottky junctions were formed by a thermal vapor-deposition of 500nm Al films on pre-coated CdS glass substrates. Diode parameters, such as the zero bias barrier height φb0, the flat band barrier height φbf and the ideality factorη, were calculated using thermionic emission theory at room temperature.

Structural and Optical Properties of e‐Beam Evaporated MX2 Thin Films

WSe2 and MoSe2 thin films were obtained by using electron beam evaporation technique at room temperature. The films were characterized by EDAX, XRD, TEM and optical absorption. The X‐ray diffraction pattern shows that prepared polycrystalline thin films have a hexagonal phase which is confirmed by TEM also. Optical properties show a direct bandgap with bandgap energy 1.89 eV and 1.98 eV for WSe2 and MoSe2 respectively.

Optical Absorption in Mo0.25W0.75Se2 Single Crystals

Single crystals of Mo0.25W0.75Se2 have been grown by direct vapour transport technique. Optical absorption spectra have been measured in the range 200–2000 nm at room temperature. Results have been analyzed on the basis of three dimensional (3D). Absorption near the fundamental edge was found to be due to indirect and direct allowed transitions on the basis of 3D model. The optical energy gaps corresponding to both transitions have also been determined. Some feeble disorder in the crystal is conceived to be present.