Annealing Effects on the Structural, Optical, and UV Photoresponse Properties of ZnO Nanostructures Prepared by RF-Magnetron Sputtering at Different Deposition Temperatures

摘要

Undoped Zn O nanostructures were deposited on Si O2/Si substrates via radio frequency magnetron sputtering at different deposition temperatures(room temperature, 200, 300, and 400 °C). The prepared samples were annealed at500 °C for 2 h under an N2 flow. The structural, surface morphological, optical, and photoresponse characteristics of Zn O nanostructures as deposited and after annealing were then investigated. The energy bandgaps of all samples after annealing(3.22–3.28 e V) decreased compared with those of the as-deposited specimens. The barrier height increased when the deposition temperature increased and reached 0.77 e V at 400 °C after annealing with a leakage current of 0.17 l A at a 5 V bias. The UV photodetector device which was deposited at the optimal temperature of 300 °C, has 12.51 9 103% photosensitivity, 2.259 l A dark current, 0.508 s response time, and 0.466 s recovery time. The dark current significantly decreased for all samples after annealing. The proposed UV photodetectors exhibit high performance, high photosensitivity, shorter response and recovery times, and excellent stability at lower bias voltages of 5 and 2 V.