Preparation and characterisation of Li-doped ZnO films

ZnO:Li films have been prepared by radio frequency (rf) diode sputtering using a Li-doped ZnO target. The film depositions were performed in pure Ar or in 28% O2/Ar sputtering gas. For comparison undoped ZnO films were also prepared. Structural, electrical, and optical measurements have been performed on films prepared under different deposition conditions and the results related with Li content and O/Zn ratio obtained by nuclear reaction and Rutherford backscattering measurements, respectively. The Li doping has not changed the films c-axis preferential orientation typical of the undoped films, but it introduces a crystallite order change. As is expected by deposition of doped oxides the sputtering gas mixture is the main parameter controlling the dopant concentration. Moreover, the oxygen presence in gas mixture has also been found to play an important role in controlling the optical properties of the film. The change in lithium concentration does not affect the electrical resistivity if the deposition parameter values have been selected in order to produce undoped zinc oxide films with a high electrical resistivity.