Effect of rapid thermal annealing on texture and properties of pulsed laser deposited zinc oxide thin films

A comparative study on the properties of pulsed laser deposited ZnO thin films as a function of rapid thermal annealing temperature (Ta) is presented. Grazing incidence x-ray diffraction pattern reveals that preferred orientation of the films changes from (002) to (103) as Ta varies from 500 to 800 °C. A clear correlation between grain morphology and texture formation is noticed. Photoluminescence spectra of all films show a strong near-band-edge ultraviolet (UV) emission and the UV emission intensity increases with Ta. Simultaneously, a weak and broad green emission centered at 505 nm corresponds to oxygen vacancies also emerged in the films annealed at Ta≥600 °C. A significant hysteresis behavior is observed in current–voltage characteristics and attributed to trapping/de-trapping driven effect. It is shown that high resistance state is dominated by space charge limited currents and low resistance state is governed by both Pool–Frenkel (2–5 V) and Schottky emission (0–2 V).

► Rapid thermal annealing effects on texture and properties of ZnO films were investigated.
► Texture changes from (002) to (103) when annealing temperature(Ta)≥700 °C.
► PL shows a strong NBE emission and its intensity increases with Ta.
► I–V characteristics display a hysteresis behavior with bias voltage.
► An electron trapping/de-trapping process at the oxygen vacancies was proposed for hysteresis behavior.