P-type transparent conducting In2O3–Ag2O thin films prepared by reactive electron beam evaporation technique

Abstract

The transparent and conducting oxide thin films are all, so far, n type. In the present article, we report the results of thin films of In2O3+Ag2O which have shown p-type conductivity and transparency in the visible range. These films are prepared on glass substrates by reactive electron beam evaporation technique at a substrate temperature of 180 °C and at a chamber pressure of 2.5×10−4 Torr with oxygen. The evaporation rate is varied by controlling the electron beam current in the range: 30–100 mA keeping the voltage at 3.8 kV. The starting material is a mixture of In2O3 and Ag2O powder (of purity 99.99%). Two compositions of Ag2O in the starting material: 20% and 40% by weight have been studied. All the films grown at higher evaporation rate are polycrystalline. The electrical and optical properties of the films show very interesting behavior. The type of conductivity (p or n) in these films is observed to be dependent upon the evaporation rate. The best values for p-type films observed in the present investigation are for the 80:20 composition at an evaporation rate 42 A/min: Hall mobility: 8.2 cm2/V s, resistivity: 22.5 Ω cm and transparency at 500 nm: 34%. The data are analyzed in the light of electronegativity equalization and partial negative charge concepts to understand the physics of the p-type conduction.