Synthesis and doping of zinc-oxide thin films by RF sputtering and ion implantation

Structural and electrical properties of ZnO:Ga thin films synthesized by RF sputtering and N-doped by ion implantation were studied. The ZnO films with an addition of 2 at% of Ga were deposited on Corning glass substrates to a thickness of 0.5 µm. Nitrogen ions were implanted at 180 keV, to 10¹⁵ – 10¹⁶ at/cm², at room temperature. It was found that the as-deposited ZnO films have a polycrystalline columnar structure. Incorporation of Ga resulted in their electrical resistivity of the order of 1 Ωcm, electron concentration of 10¹⁹ cm⁻³ and Hall mobility in the range of 1 cm²V⁻¹s⁻¹. After implantation with nitrogen the polycristalline structure was preserved, though individual columns appeared as discontinued. On the other hand, incorporation of N species into the ZnO lattice can result in both acceptor and donor states, which at this stage of experiments could not be fully clarified.