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

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 degrees C is 2.74 x 10(-4) Omega cm with a carrier density of 9.33 x 10(20) cm(-3) and a Hall mobility of 24.48 cm(2) V-1 s(-1). The resistivity can be further reduced to as low as 2.12 x 10(-4) Omega cm by post-deposition annealing at 420 degrees 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.