Performance Improvement of TiO Ultraviolet Photodetectors by Using Atomic Layer Deposited AlO Passivation Layer.

This study employed atomic layer deposition (ALD) to fabricate an AlO passivation layer to optimize the performance of ultraviolet (UV) photodetectors with a TiO-nanorod-(NR)-containing active layer and a solid-liquid heterojunction (SLHJ). To reduce the processing time and enhance light absorption, a hydrothermal method was used to grow a relatively thick TiO-NR-containng working electrode. Subsequently, a 5-nm-thick AlO passivation layer was deposited on the TiO NRs through ALD, which has excellent step coverage, to reduce the surface defects in the TiO NRs and improve the carrier transport efficiency. X-ray photoelectron spectroscopy revealed that the aforementioned layer reduced the defects in the TiO NRs. Moreover, high-resolution transmission electron microscopy indicated that following the annealing treatment, Al, Ti, and O atoms diffused across the interface between the AlO passivation layer and TiO NRs, resulting in the binding of these atoms to form Al-Ti-O bonds. This process effectively filled the oxygen vacancies in TiO. Examination of the photodetector device revealed that the photocurrent-to-dark current ratio exhibited a difference of four orders of magnitude (10 to 10 A), with the switch-on and switch-off times being 0.46 and 3.84 s, respectively. These results indicate that the AlO passivation layer deposited through ALD can enhance the photodetection performance of SLHJ UV photodetectors with a TiO active layer.