Modification of structure and properties of AZO thin film by introducing H2 in sputtering atmosphere at low substrate temperature

Al-doped ZnO (AZO) thin films were prepared on soda-lime glass at 100 °C by RF magnetron sputtering with different H2 fluxes. The influences of H2 flux on structural, electrical, and optical properties were investigated by XRD, Hall Effect measurement, and transmittance spectra. The results show that hydrogen introduction significantly modifies both structure and properties of AZO films. As H2 flux increases, the increase of unit-cell volume of the films implies that hydrogen is incorporated into ZnO lattice; the obvious decrease of crystallite size indicates that the crystallinity of the films degrades. The resistivity of the films can be continuously decreased with increasing H2 flux, accompanying with increase of both carrier concentration and Hall mobility. The main factor of increasing carrier concentration and mobility is found to be related to hydrogen incorporation and effective substitution of Zn2+ sites by Al3+. The films deposited in Ar + H2 atmosphere show improved conductive stability in air due to the passivation of inter-crystallite by hydrogen. The average transmittance in visible range of the films is hardly dependent on H2 flux. The Eg of the films increases with increasing H2 flux, and the blueshift values are close to the theoretical one according to the nonparabolic BM effect.