Impact of annealing on structural and optical properties of ZnO thin films

This paper analyzes the effect of annealing on morphological, structural and optical properties of Zinc Oxide (ZnO) thin films and their applications in optical sensing. ZnO thin films were deposited using radio frequency (RF) sputtering technique followed by annealing in presence of nitrogen environment at 100 degrees C, 200 degrees C and 300 degrees C. The effect of the annealing on surface and structural properties were studied through SEM, AFM, XRD, Raman and PL. Increment of the annealing temperature improves the texture coefficient of the film in (101) plane. Further optical sensing was performed on annealed ZnO thin films at room temperature. The results confirm that the annealing temperature of the thin films is related to crystalline structure and showed the highest optical response. The optimized annealed sample offers photo to dark current ratio (PDCR) in the order of 2.8 x 104. The annealed devices at 200 degrees C and 300 degrees C showed 102 times improved PDCR compared to devices annealed at 100 degrees C. This optimized sample showed improved results for UV range optical applications.