A Subrahmanyam

The recent investigations on Silver oxide thin films have shown promise in optical data storage. In the present paper, the electrical and optical properties of silver oxide films grown by reactive electron beam evaporation are reported. The growth parameter in the present study is the oxygen content in the film; it is achieved by varying the electron beam current in the range 30 - 100 mA keeping all other growth parameters constant. The vacuum chamber pressure (while Oxygen is present) is kept constant at 4.0 × 10-4 Torr. The films are prepared at a 180°C. The electrical and optical properties have shown a systematic variation with oxygen content in the film. The Optical band gap of the Ag2O films are observed to be in the order 3.3 eV. A high deposition rate (equivalently, low oxygen content in the film) has yielded a p-type film. These results are discussed with the partial ionization theory.

Zinc oxide thin films deposited on quartz substrates were subjected to electron beam irradiation. The effect of electron bombardment on the structural, optical and luminescent properties of the film has been investigated. The electron bombardment leads to better crystallinity, enhanced UV emission and a red shift of 0.025 eV in the band gap of ZnO thin films. The changes in the material property are ascribed to the surface annealing effect of electron beam irradiation. However, the annealing effects induced by electron beam are found to be distinct compared to the high temperature (800 °C) thermal annealing. © 2006 Elsevier B.V. All rights reserved.

Present paper reports the synthesis, electrical and optical properties of p-type conducting and transparent silver indium oxide (AIO) thin films prepared on glass substrates by reactive electron beam evaporation technique at three substrate temperatures (50, 200 and 250 °C) and at five evaporation rates (0.05 to 16.0 nm/s). The source material is pure powders of Ag 2O:In2O3=50:50 mol%. The AIO films are amorphous. The films, though not corresponding to Delafossite crystal structure, exhibit p-type conductivity, when prepared at an evaporation rate of 0.05 nm/s at all the three substrate temperatures. With increasing filament current, it is observed that (i) the electrical resistivity decreases and (ii) the refractive index of the films (at 632.8 nm, and is in the range: 1.219-1.211) decreases. The work function (effective Fermi level) has been measured on these samples by Kelvin Probe method. The results are explained on the basis of partial ionic charge and localization of covalent bonds in the AIO thin films. © 2004 Elsevier Ltd. All rights reserved.

Nano silver oxide thin films have shown plasmon assisted fluorescence phenomenon which can be used for optical data storage. In the present report, we present the results of fluorescence of nano silver thin films prepared by DC Magnetron sputtering technique at low temperature (150K). The nano silver thin films are oxidised and are irradiated with blue light (γ = 440 nm), a fluorescence emission is observed in the red region (γ = 660 nm). These films are analysed by XRD and AFM. Emission spectrum was recorded using fluorescence spectrometer. Films of thicknesses 50A to 600 A are prepared and compared the fluorescence properties. It is observed that the fluorescence emission from the silver clusters depends on growth parameters in sputtering (like substrate temperature or deposition rate) and on the oxidation temperature. © 2006 Taylor & Francis Group, LLC.

In the present work, a novel proof oc concept for rewritable ultra high density nano optical data storage devices has been discussed. Nano silver films are prepared on glass substrates by DC Magnetron sputtering technique at lower temperature (T=150 K). When these films are oxidised and are irradiated with blue light ( λ = 485 nm), a fluorescence emission is observed in the red region (λ ∼ 650 nm). These films are analysed by XRD and AFM. Emission spectrum was recorded using fluorometer. Films of thicknesses 50Å to 600 Å are prepared and compared the fluorescence properties. It is observed that the fluorescence emission from the silver clusters depends on growth parameters in sputtering (like substrate temperature or deposition rate) and on the oxidation temperature. © 2006 IEEE.

Metamorphic HEMTs on GaAs substrates are promising devices of today as they are operated at even higher frequencies for microwave applications compared to pseudomorphic HEMTs. The selective removal of n+ InGaAs ohmic contact layer from the top of the device structure poses a major challenge during fabrication. We have studied the influence of temperature on the selectivity of etch rate between the n+ InGaAs and underlying InAlAs layers using Succinic acid based etchant. The etchant was composed of Succinic acid solution mixed with hydrogen peroxide and deionised water. The pH of the solution was adjusted to 5 by adding NH4OH. The etch rates at different temperatures between 14°C to 30°C were estimated by profiling the etched pattern using Atomic Force Microscopy (AFM). Surface roughness of the etched area also was studied using AFM. It was found that the selectivity has improved with temperature. This is possibly due to simultaneous occurrence of low etch rates of InAlAs due to presence of aluminum oxide and high etch rates of InGaAs due to increased temperature. It was also found that the surface roughness was higher at lower temperatures contrary to the observations made in the case of pseudomorphic HEMTs. © 2007 IEEE.

The electrical and Hall resistivities of Tbx Fe100-x thin films in the temperature range 13-300 K were investigated. The sign of Hall resistivity at 300 K is found to change from positive for x=28 film to negative for x=30 film, in accordance with the compensation of Tb and Fe moments. All the films are seen to have planar magnetic anisotropy at 13 K. The temperature coefficients of electrical resistivities of the amorphous films with 19≤x≤51 are seen to be negative. The temperature dependence of Hall resistivity of these films is explained on the basis of random magnetic anisotropy model. The temperature dependences of Hall resistivities of the x=22 and 41 films are seen to exhibit a nonmonotonous behavior due to change in anisotropy from perpendicular to planar. The same behavior is considered for the explanation regarding the probable formation of Berry phase curvature in these films. © 2009 American Institute of Physics.

p-Type In2O3+Ag2O thin films were prepared on glass substrates by reactive electron beam evaporation. These films have shown p-type conductivity and transparency in the visible range. Varying the evaporation rate by electron beam current control, the film conductivity was observed to depend on the evaporation rate, the optimum conditions for p-type conductivity being 80:20 composition at an evaporation rate of 42 A/cm. Films obtained under this condition showed Hall mobility of 8.2 cm2/V-s, resistivity of 22.5 Ω cm and 34% transparency at 500 nm. The physics of the p-type conduction is examined employing the electronegativity equalization and partial charge concepts.

In the present investigation, extremely thin ( ∼ 3 nm) oxides of silicon are grown by using wet oxidation technique in the temperature range 600-900°C. The capacitance-voltage, current-voltage and charge trapping characteristics are used to study the electrical properties of these thin oxides. The results show that the electrical performance of the extremely thin oxide improves with the increase in the oxide growth temperature. © 2003 Elsevier Science B.V. All rights reserved.

Silver doped indium oxide (In2-x Agx O3-y) thin films have been prepared on glass and silicon substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target of pure indium and silver (80: 20 atomic %. The magnetron power (and hence the metal atom sputter flux) is varied in the range 40-80 W. The energy dispersive analysis of X-ray (EDAX) results show that the silver content in the film decreases with increasing magnetron power. The grain size of these films is of the order of 100 nm. The resistivity of these films is in the range 10-2-10-3 Ω cm. The work function of the silver-indium oxide films (by Kelvin Probe) are in the range: 4.64-4.55 eV. The refractive index of these films (at 632.8 nm) varies in the range: 1.141-1.195. The optical band gap of indium oxide (3.75 eV) shrinks with silver doping. Calculations of the partial ionic charge (by Sanderson's theory) show that silver doping in indium oxide thin films enhance the ionicity. © 2006 Elsevier Ltd. All rights reserved.