Preparation of CuAlO₂ nanocrystalline transparent thin films with high conductivity

P-type transparent CuAlO₂ semiconductor films are made by the spin-on technique from nanocrystals. The nanocrystals are synthesized by a hydrothermal metathesis reaction. Scanning electron microscopy, x-ray diffraction and energy dispersive x-ray spectrometry suggest that the films contain nanocrystalline phases of CuAlO₂. Both the Hall technique and Seebeck measurements reveal that the film is p-type and a very high room-temperature conductivity of 2.4S cm⁻¹ is achieved. This success in fabricating a high-conductivity transparent CuAlO₂ film indicates that nanotechnology will be helpful in enhancing the conductivity of p-type transparent semiconductors. The Hall measurement of the film shows a sheet mobility of 3.6 cm² V⁻¹ S⁻¹ and a carrier concentration of 5.4 × 10¹⁸ cm⁻³. The optical band-gap of the film is estimated to be 3.75 eV and the activation energy for the positive hole is 0.14 eV.