Amorphous CuxGa1-xO film deposition by ultrahigh vacuum radio frequency magnetron sputtering

Amorphous Ga2O3 and CuxGa1-xO thin films were prepared on glass substrates by ultrahigh-vacuum radio frequency magnetron sputtering at room temperature. The films of amorphous Ga2O3 show a very high transmittance (nearly 90%). As the oxygen partial pressure increases, a dramatic shift is observed in the optical band gap of the films. The band gap energies of the films are determined by a liner fit of the transmittance spectra and are estimated to be between 4.9 and 5.3 eV. Band gap energies of amorphous CuxGa1-xO films are also estimated by the same method. They show prominent bowing characteristics with a bowing parameter as large as 9.1 eV. The band gap energy of amorphous Cu0.5Ga0.5O is formed to be much smaller than that of crystalline CuGaO2. (author)