Defect-Assisted Broad-Band Photosensitivity with High Responsivity in Au/Self-Seeded TiO2 NR/Au-Based Back-to-Back Schottky Junctions

Abstract

TiO2 nanorods (NRs) have generated much interest for both fundamental understanding of defect formation and technological applications in energy harvesting, optoelectronics, and catalysis. Herein, we have grown TiO2 NR films on glass substrates using a self-seeded approach and annealed them in H2 ambient to modify their surface defects. It has been shown that broad-band photosensing properties of Au/self-seeded TiO2 NR/Au-based two back-to-back Schottky junctions (SJs) for a broad wavelength of light are much superior as compared to those of the pristine and the control samples. Photoresponsivity values for the H2-annealed sample are 0.42, 0.71, 0.07, and 0.08 A/W for detecting, respectively, 350, 400, 470, and 570 nm lights. Very low dark current and high photocurrent lead to a gain value as high as 1.85 × 104 for 400 nm light. Unprecedentedly modified NR-based SJs show excellent photoresponsivity for detecting as low as 25, 36, 48, and 28 μW/cm2 power densities of 350, 400, 470, and 570 nm lights, respectively. It is found that Ti3+ defects play a key role in an efficient photoelectron transfer from TiO2 to Au. Our work, for the first time, highlights the simplicity and reveals the rationale behind the excellent properties of Au/self-seeded TiO2 NR film/Au back-to-back SJs.