Influence of annealing on structural, electrical and optical properties of Dy-doped ZnO thin films

Abstract

Transparent conductive Dy-doped zinc oxide thin films have been deposited on glass substrates by pulsed laser deposition technique. The effects of post-deposition annealing treatment on structural, electrical and optical properties of the ZnO : (Dy) thin films were investigated. The films show high transparency and conductivity. Van der Pauw measurements reveal that the films are n-type degenerate semiconductors. The electrical resistivity of the films deposited at 300 °C is 2.74 × 10−4 Ω cm with a carrier density of 9.33 × 1020 cm−3 and a Hall mobility of 24.48 cm2 V−1 s−1. The resistivity can be further reduced to as low as 2.12 × 10−4 Ω cm by post-deposition annealing at 420 °C for 2 h in nitrogen. Post-annealing increased the grain size and surface roughness of the films. The average transmission of the ZnO : (Dy) films (with a thickness about 529 nm) in the visible range is above 80%. The optical direct band gap value of the films is about 3.7 eV, which is slightly dependent on the annealing treatment in nitrogen.