Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
Browse
49 results
Search Results
Item Structure and properties of vacuum deposited cadmium telluride thin films(2006) Shreekanthan, K.N.; Bangera, K.V.; Shivakumar, G.K.; Mahesha, M.G.Systematic and detailed study of the growth and properties of vacuum deposited cadmium telluride thin films was made. Both p- and n-type films were grown and these films were characterized for their structural, optical, and electrical properties. The crystallographic structure of the deposits was found to be dependent on the rate of deposition. Low deposition rates were observed to result in hexagonal deposits whereas high rates of deposition favoured cubic structure for the film. Electrical and optical properties were also found to be dependent on the deposition parameters.Item Characterization of p-CdTe/n-CdS hetero-junctions(2009) Mahesha, M.G.; Bangera, K.V.; Shivakumar, G.K.Nano-crystalline CdTe/CdS thin film hetero-junctions have been grown on glass substrate by thermal evaporation technique. The growth conditions to get stoichiometric compound films have been optimized. The grown hetero-junctions have been characterized for their I-V characteristics. Analysis of I-V characteristics has been made to investigate the current conduction mechanism in p-CdTe/n-CdS hetero-junction. The band gap energy of cadmium telluride and cadmium sulfide films have been computed from the study of variation of resistance with temperature. Based on the study, band diagram for p-CdTe/n-CdS hetero-junction has been proposed.Item The effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited ZnTe thin films(2009) Rao, G.K.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited zinc telluride (ZnTe) thin films. X-ray diffraction (XRD) analysis of the films, deposited on glass substrates, revealed that they have cubic structure with strong (111) texture. Room temperature deposits are tellurium rich and an increase in the substrate temperature up to 553 °K results in stoichiometric films. Electrical conductivity has been observed to increase with the increase in substrate temperature, accompanied by increase in the carrier concentration and the mobility of the carriers. The optical bandgap energy and the thermal activation energy of the films have also been evaluated. © 2009 Elsevier Ltd. All rights reserved.Item Preparation and characterization of CdxZn1-xS thin films by spray pyrolysis technique for photovoltaic applications(2009) Raviprakash, Y.; Bangera, K.V.; Shivakumar, G.K.CdxZn(1-x)S (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) thin films were deposited by the chemical spray pyrolysis technique using a less used combination of chemicals. Depositions were done at 573 K on cleaned glass substrates. The composition, surface morphology and structural properties of deposited films were studied using EDAX, SEM and X-ray diffraction technique. XRD studies reveal that all the films are crystalline with hexagonal (wurtzite) structure and inclusion of Cd into the structure of ZnS improved the crystallinity of the films. In the entire compositions, the (0 0 2) diffraction peak is prominent which gives lattice matching to the chalcogenide semiconductor such as CuInxGa1-xSe2 and CuIn (s1-xSex)2, which are used in photovoltaic devices. The value of lattice constant 'a' and 'c' have been observed to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm, respectively. The band gap of the thin films varied from 3.32 to 2.41 eV as composition varied from x = 0.0 to 1.0. It was observed that presence of small amount of cadmium results in marked changes in the optical band gap of ZnS. © 2009 Elsevier Ltd. All rights reserved.Item Growth, structural and optical properties of CdxZn1-xS thin films deposited using spray pyrolysis technique(2010) Raviprakash, Y.; Bangera, K.V.; Shivakumar, G.K.CdxZn(1-x)S (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) thin films were deposited by the chemical spray pyrolysis technique using a less used combination of chemicals. Depositions were done at 573 K on cleaned glass substrates. The composition, surface morphology and structural properties of deposited films were studied using EDAX, SEM and X-ray diffraction technique. XRD studies reveal that all the films are crystalline with hexagonal (wurtzite) structure and inclusion of Cd into the structure of ZnS improved the crystallinity of the films. The value of lattice constant 'a' and 'c' have been observed to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm, respectively. The band gap of the thin films varied from 3.32 to 2.41 eV as composition varied from x = 0.0-1.0. It was observed that presence of small amount of cadmium results in marked changes in the optical band gap of ZnS. © 2009 Elsevier B.V. All rights reserved.Item Growth and morphology of mixed K1-x(NH4)xH2PO4 crystals(Elsevier Ltd, 2010) Shenoy, P.; Bangera, K.V.; Shivakumar, G.K.Mixed crystals of ammonium dihydrogen orthophosphate (ADP) and potassium dihydrogen orthophosphate (KDP), i.e., potassium ammonium dihydrogen phosphate, K1-x(NH4)xH2PO4 have been grown by slow evaporation from the supersaturated solution at an ambient temperature 26 ± 1 °C for ammonium concentration x in the range 0.0 ? x ? 1.0. The morphology changes from tetragonal prism to needles when the concentration of either of the components approaches that of the other. Induction periods were measured for various compositions of mixed crystals of ADP and KDP by the direct vision method. Crystal compositions were determined by flame atomic absorption spectroscopy and also by chemical analysis. Results of the X-ray analysis of the grown crystals are also reported. Maximum size of the grown mixed crystal was around 16 × 10 × 4 mm3. © 2010 Elsevier B.V. All rights reserved.Item Studies on vacuum deposited p-ZnTe/n-ZnSe heterojunction diodes(2010) Rao, K.G.; Bangera, K.V.; Shivakumar, G.K.p-ZnTe/n-ZnSe heterojunction diodes were prepared by vacuum deposition and a detailed electrical characterization of the heterojunction was performed. The I-V and C-V characteristics of the heterojunction diodes were studied to determine the conduction mechanism, barrier height, space charge density and thickness of the depletion region in the heterojunction. The bandgap and activation energies of n-ZnSe and p-ZnTe were also determined and a theoretical band diagram of p-ZnTe/n-ZnSe heterojunction was drawn based on Anderson's model. © 2010 Elsevier Ltd. All rights reserved.Item Growth and thermal studies on pure ADP, KDP and mixed K 1-x(NH4)xH2PO4 crystals(2010) Shenoy, P.; Bangera, K.V.; Shivakumar, G.K.The investigations on the formation of mixed crystals of ammonium dihydrogen orthophosphate (ADP) and potassium dihydrogen orthophosphate (KDP) i.e. potassium ammonium dihydrogen phosphate, K1-x(NH 4)xH2PO4 have been presented in this paper. Pure and mixed crystals of ADP and KDP have been grown by slow evaporation technique from the supersaturated solution at an ambient temperature 26±1 °C for ammonium concentration x in the range 0.0 ? × ? 1.0 in the case of mixed crystals. Crystal compositions were determined by flame atomic absorption spectroscopy and chemical analysis. The results of the X-ray analysis of the grown crystals are also reported. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the kinetic process of dehydration and the high temperature phase behaviour. DTA showed the distinct thermal events attributed to dehydration of ADP, KDP and K1-x(NH4)xH2PO4. The results of thermal analysis and chemical analysis are consistent with each other. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Studies on the photoconductivity of vacuum deposited ZnTe thin films(2010) Rao, K.G.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the analysis of photoconductivity of vacuum deposited zinc telluride (ZnTe) thin films as a function of substrate temperature and post-deposition annealing. Detailed analyses were first carried out to understand the effect of substrate temperature and annealing on the structure, composition, optical and electrical properties of the films. The films deposited at elevated substrate temperatures showed faster and improved photoresponse. Post-deposition annealing was found to further enhance the photoresponse of the films. Attempts have been made to explain the improvement in the photoresponse on the basis of structural and compositional changes, taking place in the films, due to the substrate temperature and annealing. © 2010 Elsevier Ltd. All rights reserved.Item Studies on vacuum deposited p-ZnTe/n-CdTe heterojunction diodes(2011) Rao, K.G.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the fabrication and detailed electrical characterization of p-ZnTe/n-CdTe heterojunction diodes prepared by vacuum deposition method. The possible conduction mechanisms of the heterojunction diode were determined by analyzing the I-V characteristics. The C-V characteristics of the heterojunction diodes were studied to determine the barrier height, carrier concentration and thickness of the depletion region in the heterojunction. A theoretical band diagram of the heterojunction was drawn based on Anderson's model. © 2010 Elsevier Ltd. All rights reserved.