A Subrahmanyam

Cu2ZnSnS4 (CZTS) is a potential absorber material among its contemporary contenders for thin film solar cells. Controlling secondary phases in CZTS is a major concern. In the present study, CZTS thin films are prepared by a single step deposition technique: sputtering of individual metal targets of copper, zinc and tin in the sulfide plasma. The control on secondary phase formation and better microstructure properties are realized in the CZTS thin films prepared at low tin-target powers. The vibrational modes investigated by Raman measurement reveal transformation of CZTS thin films from less stable stannite phase to the stable kesterite phase under low Sn-power (30 W and 40 W) conditions.

The editorial of Solar Energy Materials & Solar Cells deals with topics associated with solar energy conversion. Solar energy conversion has now become a viable method to satisfy a substantial amount of a substantial amount of our energy needs while reducing carbon dioxide pollution, creating jobs and decreasing market instabilities tied to the geopolitics of fossil fuels. There is a growing awareness that fossil fuels are undesirable and that their supplies are rapidly diminishing or are environmentally or economically unsustainable.

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.

Tin doped indium oxide (ITO) thin films are being used extensively as transparent conductors in several applications. In the present communication, we report the electrical transport in DC magnetron sputtered ITO thin films (prepared at 300 K and subsequently annealed at 673 K in vacuum for 60 minutes) in low temperatures (25-300 K). The low temperature Hall effect and resistivity measurements reveal that the ITO thin films are moderately dis-ordered (kFl∼1; kF is the Fermi wave vector and l is the electron mean free path) and degenerate semiconductors. The transport of charge carriers (electrons) in these disordered ITO thin films takes place via the de-localized states. The disorder effects lead to the well-known 'metal-insulator transition' (MIT) which is observed at 110 K in these ITO thin films. The MIT in ITO thin films is explained by the quantum correction to the conductivity (QCC); this approach is based on the inclusion of quantum-mechanical interference effects in Boltzmann's expression of the conductivity of the disordered systems. The insulating behaviour observed in ITO thin films below the MIT temperature is attributed to the combined effect of the weak localization and the electron-electron interactions.

Hole conducting, optically transparent Cu2O thin films on glass substrates have been synthesized by vacuum annealing (5×10-6 mbar at 700 K for 1 hour) of magnetron sputtered (at 300 K) CuO thin films. The Cu2O thin films are p-type and show enhanced properties: grain size (54.7 nm), optical transmission 72% (at 600 nm) and Hall mobility 51 cm2/Vs. The bulk and surface Valence band spectra of Cu2O and CuO thin films are studied by temperature dependent Hall effect and Ultra violet photo electron Spectroscopy (UPS). CuO thin films show a significant band bending downwards (due to higher hole concentration) than Cu2O thin films.

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.

Studies on the Schottky barrier properties of ITO/n-GaAs junctions and their photovoltaic behaviour are reported. The junctions were prepared by depositing ITO by reactive thermal evaporation technique on as-cleaned and heat-treated GaAs substrates of (100) orientation. The barrier height of the Schottky diodes prepared on as-cleaned GaAs is 0.83+or-0.02 eV as measured by I-V and C-V methods, and is nearly the same as in the case of many other metal/n-GaAs interfaces. Heat-treated GaAs having arsenic deficient surfaces produced a larger barrier height ( approximately=1.05 eV). As a result of the barrier height enhancement, the ITO/n-GaAs junctions exhibited an increase in the open circuit voltage and photoconversion efficiency from 435 mV and 4.94% to 585 mV and 7.75%, respectively. The efficiency of 7.75% is perhaps the highest for any ITO/GaAs junctions reported so far. The results are discussed on the basis of the defect models for Schottky barrier formation.

Copper oxide thin films are a topic of intense investigation by several researchers. Copper reacting with oxygen, depending upon the available energy, forms CuO, Cu2O and Cu4O3 phases. Among these, Cu4O3 is a difficult phase to prepare. In the present communication, we report the preparation and properties of the stable phase of Cu4O3. These Cu4O3 thin films have been prepared at room temperature (300 K) on borosilicate glass by reactive DC magnetron sputtering. Cu4O3 thin films (of thickness 265 ± 5 nm) are p-type semiconductors (hole density 2.4 × 1018 cc-1 and Hall mobility 0.04 cm2 V-1 s-1) and show a low resistivity (55 ω cm). They have a direct band gap of 2.34 eV and an indirect band gap of 1.50 eV. The surface work function of Cu4O3 (measured by Kelvin Probe technique) is 5.35 ± 0.01 eV. Cu4O3 films are irradiated with laser radiation of 532 nm wavelength and 10 MW cm-2 (120 s) power density. It shows a phase transformation to CuO which is confirmed by the Raman Spectroscopy measurements.

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.