Electrical properties of undoped In2O3 films prepared by reactive evaporation

Electrical properties of reactively evaporated In 2 O 3 films are studied in relation to evaporation conditions and the carrier scattering mechanism is discussed. The films are made on heated glass substrates by evaporation of In metal in oxygen at about 1*10 -3 Torr. The films become polycrystalline above substrate temperature 200 degrees C, showing 75% transparency at 550 nm. Electrical resistivity of the films, rho =2-3*10 -3 Omega cm is obtained for substrate temperatures 200-400 degrees C. Hall coefficient measurements show the film to be a n-type conductor and have relatively high mobility, 25.60 cm 2 V -1 s -1 . The degeneracy of free carriers in the film is established by the high carrier concentration (above 3.5*10 19 cm -3 ) and absence of temperature dependence of electrical properties. Discussion of the mobility-carrier concentration relationship from the experiments and theory leads to the conclusion that the dominant scattering process in the films is due to ionised impurity scattering centres.