Single step deposition method for nearly stoichiometric CuInSe2 thin films
Abstract This paper reports the production of high quality copper indium diselenide thin films using pulsed DC magnetron sputtering from a powder target. As-grown thin films consisted of pin-hole free, densely packed grains. X-ray diffraction showed that films were highly orientated in the (112) and/or (204)/(220) direction with no secondary phases present. The most surprising and exciting outcome of this study was that the as-grown films were of near stoichiometric composition, almost independent of the composition of the starting material. No additional steps or substrate heating were necessary to incorporate selenium and create single phase CuInSe2. Electrical properties obtained by hot point probe and four point probe gave values of low resistivity and showed that the films were all p-type. The physical and structural properties of these films were analyzed using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Resistivity measurements were carried out using the four point probe and hot probe methods. The single step deposition process can cut down the cost of the complex multi step processes involved in the traditional vacuum based deposition techniques.
Single crystal growth of CuInSe2 by selenization horizontal Bridgman method
Abstract Bulk single crystals of CuInSe 2 are grown by the selenization horizontal Bridgman method where the temperature profile is moved electrically with controlling Se vapor pressure. The p-type single crystals with large Hall coefficients and mobilities are prepared at Se vapor pressures of 10 and 25 Torr. Overshoots are observed in the Hall coefficient versus temperature curves for most of the p-type crystals. The peak temperature at the overshoot depends on the donor density, which is controlled by Se vapor pressure ranging from 5 to 25 Torr. Acceptors of the p-type crystals have two kinds of activation energies of ∼ 20 meV for Cu vacancy or copper in the In site, and ∼ 60 meV for the In vacancy. The number ratio of those densities is determined by the variation of the Hall coefficient versus temperature curves.
The structure of electricity demand in the Brazilian household sector
Abstract The present structure of residential electricity demand is analysed by electricity consumption classes and end-uses. Nearly 70% of households consume less than 150 kWh/month and are responsible for 35% of total residential demand. Other determinants of electricity-use, such as income and place of residence, are also discussed. It is found that electricity demand is increasing faster than income as the country reaches appliances saturation in upper consumption levels. Water heating and refrigeration account for the major part of residential consumption. Residential conservation efforts have started introducing more efficient lighting equipment and refrigerators, but further work will have to be done to speed up the diffusion of efficient technology at costs that can be paid by consumers.