Effect of Deposition and Annealing Temperature on Structural, Electrical and Optical Properties of Ag Doped ZnO Thin Films

The effects of the deposition and annealing temperature on the structural, electrical and optical properties of Ag doped ZnO (ZnO : Ag) thin films were investigated. All of the films were deposited with a 2wt% Ag2O-doped ZnO target using an e-beam evaporator. The substrate temperature varied from room temperature (RT) to 250 degrees C. An undoped ZnO thin film was also fabricated at 150 degrees C as a reference. The as-grown films were annealed in temperatures ranging from 350 to 650 degrees C for 5 h in air. The Ag content in the film decreased as the deposition and the post-annealing temperature increased due to the evaporation of the Ag in the film. During the annealing process, grain growth occurred, as confirmed from XRD and SEM results. The as-grown film deposited at RT showed n-type conduction; however, the films deposited at higher temperatures showed p-type conduction. The films fabricated at 150 degrees C revealed the highest hole concentration of 3.98x1019 cm(-3) and a resistivity of 0.347 Omega center dot cm. The RT PL spectra of the as-grown ZnO : Ag films exhibited very weak emission intensity compared to undoped ZnO; moreover, the emission intensities became stronger as the annealing temperature increased with two main emission bands of near band-edge UV and defect-related green luminescence exhibited. The film deposited at 150 degrees C and annealed at 350 degrees C exhibited the lowest value of I-vis/I-uv of 0.05.