Effect of annealing temperature on the structural, optical and electrical properties of ZnO thin films grown chemically on PS substrate

Abstract

ZnO thin films were successfully produced on porous silicon (PS) substrates by a chemical bath deposition method. ZnO thin films were then annealed at 300, 500, and 700 °C for 20 min in nitrogen (N2) atmosphere. X-ray diffraction, field emission scanning electron microscopy (FESEM), and photoluminescence (PL) were utilized to investigate the effect of post-annealing temperature on the structural, optical, and electrical properties of ZnO thin films. The lattice constant, full width at half maximum, and strain (the grain size) of (0 0 2) peak of ZnO thin films decreased (increased) with increasing the annealing temperature, respectively. The FESEM images revealed that the ZnO thin films are compact array ZnO nanocolumns and were perpendicularly grown to the PS substrate. The biggest ratio of the PL intensity of UV emission to that of visible emission is observed from ZnO thin films annealed at 500 °C. The PL results of the ZnO thin films exhibit that the UV peak positions shift slightly toward lower wavelengths with increase of the annealing temperature. The current–voltage measurements demonstrate that the current level increases as the annealing temperature increases to 500 °C, and then decreases when the temperature further increases up to 700 °C.