Conductive and transparent Al — doped ZnO thin films prepared by rf magnetron sputtering

Abstract

Highly conductive ZnO thin films with Al 2O 3 contents of 0–10 atomic% have been prepared by rf magnetron sputtering. The resistivity of the as — deposited films varies from 3.2 × 10 4 to 1.1 × 10 −2 Ω-cm dependent on different experimental conditions. The minimum transmittance in the visible region (450–800 nm) is above 80% for all films, while a 92% transmission is observed in the sample with a thickness of 400 nm. Transmittance of the sample with a resistivity of 1.1× 10 −2 Ω-cm is above 86 % in the visible region. All films have a strongly preferred orientation of the c axis perpendicular to the target surface. A defect chemistry model is proposed to investigate the effect of Al 2O 3 dopants in the ZnO film. Doping of Al 2O 3 up to several at% forms a substitutional solid solution with excess electrons dominating the electrical condition. The introduction of more Al 2O 3 results in the formation of the oxygen interstitial, which leads to an expansion in the lattice and peak shift in the X — ray diffraction profile.