K.V. Madhuri

Photochromic properties of double layer CdS/MoO3 nano-structured films

Abstract The double layer CdS/MoO 3 devices were deposited on Pyrex glass substrates by sequential evaporation of CdS and nano-structured molybdenum trioxide (MoO 3 ) films using thermal and activated-reactive evaporation, respectively. The morphology and particle sizes of CdS and MoO 3 were determined by atomic force microscopy. The photochromic properties of the CdS/MoO 3 double layer were studied in the spectral range 300–1500 nm by illuminating them with the polychromatic light emitted by a tungsten lamp at various irradiation durations. The photochromic behaviour is observed to be more effective for generating colour centres in the In:CdS/MoO 3 double layer system.

Physical investigations on electron beam evaporated V2O5–MoO3 thin films

Abstract Thin films of the system (V 2 O 5 ) 1− x –(MoO 3 ) x with 0⩽ x ⩽l were prepared by electron-beam evaporation technique in an oxygen partial pressure of 2×10 −4 mbar onto silicon substrate maintained at temperature of 423 K. X-ray photoelectron spectroscopy and infrared data of these samples suggest that the film composition nearly approaches the nominal stoichiometry. The optical absorption studied in the wavelength range 300–1500 nm shows that the optical band gap increases with the increase of the MoO 3 content in V 2 O 5 –MoO 3 films. The electrical measurements exhibit a decrease of the conductivity with increasing MoO 3 concentration. Results suggest the formation of the (V 2 O 5 ) 1− x –(MoO 3 ) x solid solution.

Characterization of laser-ablated V2O5 thin films

Vanadium pentoxide thin films have been prepared by the pulsed laser deposition technique. The influence of substrate temperature on the growth of V2O5 films was studied. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements have been carried out in order to understand the growth mechanism. The crystallization in V2O5 thin films starts at deposition temperatures as low as 473 K and the grain size increased with deposition temperature. The films exhibited predominantly (0 0 1) orientation, representing the orthorhombic layered structure. The infrared (IR) and Raman measurements supported the above data.

Preparation and Characterization of R.F. Magnetron Sputtered Mo:ZnO Thin Films

The ZnO and Mo:ZnO thin films were deposited by radio frequency magnetron sputtering on quartz and intrinsic silicon (100) substrates at a fixed combined partial pressure mbar of Ar

Transition metal oxide thin films-applications

This project reveals how progressive oxidation and reduction, which alters the physical and chemical structures modulates the free radical and reactivity of GO. The ability of graphene nanosheets rich in radicals were examined as both initiator and cross linker to fabricate polymer composites.W focus on crystal growth and evaluation of 2D-layered compounds. For crystal growth, liquid phase growth with temperature difference method under controlled vapour pressure (TDM-CVP) has been studied GaSe and InSe are grown by this method. GaSe can generate wide frequency tunable terahertz (THz) wave. Due to the superior characteristic features of THz wave of high transparency like radio wave for non-polarized substances and high reflectivity to metal as light wave, THz wave can be applied for wide variety of non-destractive and non-invasive inspection. For example, disconnections and corrosion of electric wires covered with opaque insulating shield, water content in concrete, degradation of polyethelene can be measured non-destractively by using THz wave.S the ground-breaking article in Science in October 2004 describing the occurrence, isolation and potential significance of graphene, there has been a huge interest in developing industrially scalable methods of manufacture from bottom-up and top-down routes. One such top-down route developed for the mass manufacture of graphene involves electrochemical exfoliation. This can be conducted in anodic (oxidative) and cathodic (reductive) regimens, with the latter more suitable for production of higher quality (containing fewer defects) graphene, but hindered by lower efficiency and yield. This makes the selection of an appropriate electrolyte particularly important. Previous work has shown that graphene prepared by electrochemical exfoliation can be simultaneously functionalized with groups tailored to improve solubility in aqueous systems. In this case, functionalization significantly enhances the specific capacitance of the material when used as an electrode in super capacitors.This presentation details the expansion of this work in two ways.G (monolayer and few layers) is a two-dimensional material with the large anisotropy between in-plane and outof-plane directions. Carbon nanowalls (CNWs) are few-layer graphenes with open boundaries, standing vertically on a substrate. The sheets form a self-supported network of mazelike-wall structures. CNWs and similar graphene structures can be synthesized by several plasma enhanced chemical vapor deposition (PECVD) techniques. CNWs are sometimes decorated with metal nanoparticles and biomolecules. The structure of CNWs with large surface area would be suitable for the platform in electrochemical and biosensing applications. CNW films can be potentially used as electrodes of electrochmical sensor, capacitor, dye-sensitized solar cell, polymer electrolyte fuel cell (PEFC), and implantable glucose fuel cell (GFC). Among these, CNW electrodes in fuel cells should be decorated with catalytic nanoparticles such as Pt. From a practical point of view, control of CNW structures including spacing between adjacent nanowalls and crystallinity is significantly important. Moreover, formation method of catalytic metal nanoparticles should be established. We carried out CNW growth using PECVD employing CH4/H2/Ar mixtures with emphasis on the structure control of CNWs. We report the effects of ion bombardment and catalytic metals on the nucleation of vertical nanographenes to realize active control of interspace between adjacent walls. Moreover, CNW surface was decorated with Pt nanoparticles by the reduction of chloroplatinic acid or by the metal-organic chemical deposition employing supercritical fluid. We also report the performances of hydrogen peroxide sensor, PEFC and GFC, where CNW electrode was used.

Morphological, optical and electrochromic properties of dry-lithiated nanostructured WO3 thin films

Abstract Tungsten trioxide (WO3) thin films were prepared by thermal evaporation technique on thoroughly cleaned glass substrates at high pressure of 133.322 mPa in presence of argon. The substrate temperature was maintained from 6 °C to 8 °C with the help of a cold jar. The deposited films were annealed at 400 °C in air for about 2 hours. The films were characterized in terms of their composition by X-ray photoelectron spectroscopy. Subsequently, the laboratory developed dry lithiation method was used to intercalate lithium atoms into as-deposited films in various proportions. With the amount of lithium content inserted into the film, the films showed coloration in visible and near infrared regions. The morphology, coloration efficiency and optical constants of annealed and lithiated films were calculated.

Effect of annealing on the physical properties of WO 3 thin films

Tungsten trioxide (WO3) thin films were deposited by electron beam evaporation technique at an oxygen partial pressure of 2 × 10−4 mbar and at different substrate temperatures ranging from room temperature (RT) to 450°C. The films were annealed at 400°C about 2 hours and the properties were studied systematically. The x-ray diffraction studies show the diffraction peak of (320) at 2θ = 44.07° which indicate the orthorhombic phase of WO3 and also the other peaks represent the hexagonal phase of WO3. Due to annealing of the films, the monoclinic phase is also observed. The surface morphology of WO3 thin films was investigated by using atomic force microscopy and scanning electron microscopy, which supports the above data. The energy-dispersive x-ray (EDX) compositional analysis confirmed the presence of W and O. The optical properties were studied by UV-VIS spectrophotometer and hence the bandgap values are calculated.