Advanced Materials Research Vol. 665

Abstract: A systematic theoretical study of 4d transition metal nitride, PdN has been carried out using ab initio full potential LAPW method (FP-LAPW) within the generalized gradient approximation (GGA). PdN crystallizes in zinc-blende structure, which is found to be most stable one. We have calculated the ground state properties in terms of lattice constant (a₀), Bulk modulus (B₀) and its Pressure derivative (B₀). The electronic properties such as band structure and density of states reveal that PdN is metallic in nature with large overlap of Pd-d electron at Fermi level. The elastic constant are in good agreement with previous theoretical results for zinc-blende structure.

Abstract: Thin films of La_0.8-xPr_0.2Sr_xMnO₃ (LPSMO) (x = 0.1, 0.2, 0.3) manganite, synthesized using pulsed laser deposition (PLD) technique, were irradiated by 200MeV Ag⁺¹⁵ ions with an ion fluence of 5 × 10¹¹ ions/cm². Structural and microstructural characterizations have been carried out using XRD and AFM show single crystalline nature of the films having island like grain growth. The structural and grain morphology modifications due to irradiation has been observed. Temperature dependent resistivity measurements have been carried out for all the films before and after irradiation, which reveal a reduction in the resistivity and enhancement in insulator - metal (I-M) transition temperature (T_P) with Sr content (x) resulting in improved transport (reduced resistivity and enhanced T_P) in the films which can be attributed to the irradiation induced improved crystallinity and grain morphology. Temperature coefficient of resistance (TCR) improves on irradiation which is useful for practical applications.

Abstract: A new proposal of a local pseudopotential is put forwarded here depending on the concept of extended core radius in which half of the nearest neighbour distance is treated as effective core radius. There is no input of any property for fitting this parameter in this formalism. This pseudopotential is found to satisfy all the necessary requirements for applications. With this model potential we have evaluated the form factors for several bcc, fcc and hcp metals and achieved excellent agreement with previous results. On the same footing, we have examined other 14 local pseudo potentials also and on the basis of the comparison, the presently proposed pseudopotential is found to be much better. As a test case study, we have evaluated phonon dispersion curves of some liquid metals, viz. Na (Z = 1), Mg (Z = 2), Al (Z= 3) and Pb (Z = 4) and obtained quite satisfactory results.

Abstract: A new kind of two phase ammonium dihydrogen phosphate (NH₄H₂PO₄ or ADP)/polyvinyl alcohol (PVA) composite films have been prepared by solution cast technique. Significant enhancement of dielectric permittivity (~442) of ADP/PVA composites are observed at low ADP concentration (f_ADP f_C ~5 wt %) which is the percolation threshold value estimated from the concentration dependent transport and dielectric data. Nearly 85 times increase in dielectric permittivity compared to that of the bare PVA film in the composite film around f_C with low loss (~0.14) at 1 kHz and room temperature is observed. The present ADP based PVA composite material might be processed for application in devices.

Abstract: The knowledge of the physical properties of liquid Al-Mg binary alloys is of high scientic and practical importance. The Ziman formalism is used to study the concentration dependent electrical resistivity of liquid Al-Mg alloys through an electron-ion potential. Partial structure factor is calculated by using Ashcroft-Langreth equation. The results are compared with experimental findings and the effect of screening function on electrical resistivity is discussed. This reveals that the resistivity data of liquid Al-Mg system are in qualitative agreement with the nearly-free electron picture.

Abstract: The structural and electrical properties of ZnTe thin films were investigated as a function of substrate temperature. Vacuum evaporated thin films of Zinc Telluride (ZnTe) of 10kÅ thickness have been deposited on ultrasonically cleaned glass substrates at various substrate temperatures (303K, 373K 448K). Structural parameters were obtained using XRD analysis. It was observed that the films deposited were cubic in nature with a strong (111) texture. Electrical parameters (Hall Effect measurement) have been obtained and studied at various temperatures in the range 303-393K. It is observed that Hall coefficient remains positive throughout the whole temperature range indicating that holes are the majority carriers. The results obtained from structural and electrical parameters study have been correlated and it is found that the thin films deposited at higher substrate temperatures possess increasingly good crystalline structure with improved electrical conductivity along with an increase in carrier concentration and mobility of carriers.

Abstract: Volatile Organic Compounds (VOCs) are highly reactive, often mixed with interfering gases and more importantly, their vapours in the gaseous form respond to the gas sensor devices. Oxide semiconductor based thin film gas sensors play vital role in detecting, monitoring and controlling the presence of hazardous and harmful gases in the environment at very low concentration and hence are tested for the detection of harmful or industrially important VOCs. The demand of sensitive as well stable gas/vapour sensors for direct sensing application has increased the importance of In₂O₃:SnO₂ based semiconductor materials. The paper presents the fabrication aspects of thin film gas sensors based on x1In₂O₃:x2SnO₂ compound and also their application for the detection of some important volatile organic compounds. Thin films of x1In₂O₃:x2SnO₂ were deposited using Thermal Evaporation technique and under the optimized fabrication conditions, the vapour sensors were prepared and mounted on the proper contact jig. Their response to the presence of Volatile Organic Compounds like CCl₄ was examined. The stability, the sensitivity and the response time of the sensors were studied for the different concentrations of test vapours.

Abstract: SnS (tin sulphide) is of interest for use as an absorber layer and the wider energy band gap phases e.g. SnS₂, Sn₂S₃ and Sn/S/O alloys of interest as Cd-free buffer layers for use in thin film solar cells. Thin films of tin sulphide have been deposited using CBD at three different bath temperatures (27, 35 and 45 °C) onto microscope glass substrates. The X ray diffraction (XRD) analysis of the deposited films reveled that all films has orthorhombic SnS phase as dominant one with preferred orientations along (111) direction. The temperature influence on the crystalline nature and the presence of other phases of SnS has been observed. The average grain size in the films determined from Scherers formula as well as from Williamson-Hall-plot method agrees well with each other. Energy dispersive X-ray (EDAX) analysis used to determine the film composition suggested that films are almost stoichiometric. The scanning electron microscopy (SEM) reveals that deposited films are pinhole free and consists of uniformly distributed spherical grains. The optical analysis in the 200-1200 nm range suggests that direct allowed transitions are dominant in the absorption process in the films with variation in the band gap (~1.79 to ~2.05 eV) due to variation in deposition temperature.

Abstract: The sulfonamide compound, 4-methyl-N-(2-methylphenyl) benzene sulfonamide has been synthesized and characterized by FTIR, NMR, UV-Vis, single crystal X-ray diffraction and thermal analysis. Density functional (DFT) calculations have been carried out for the title compound by performing DFT level of theory using B3LYP/6-31G (d,p) basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with the experimental IR spectra and they support each other. In addition, atomic charges, frontier molecular orbitals and molecular electrostatic potential were carried out by using density functional theory (DFT/B3LYP) 6-31G (d, p) basis set. The calculated Homo and Lumo energies show that charge transfer occur in the molecule.

Abstract: 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.