Effect of Solution on One-Step Hydrothermal Growth of ZnO Nanorod Arrays and its Application to Ultraviolet Photodetectors

Abstract

In this work, we report the characteristics of ZnO nanorod (NR) arrays grown on bare Si (100) substrates by a one-step hydrothermal method, using equimolar aqueous solutions of zinc nitrate hexahydrate (Zn[NO3]2·6H2O) and hexamethy lenetetramine (C6H12N4) with concentrations of 0.01, 0.03, 0.05, and 0.10 M. For the top two precursor concentrations, 0.05 and 0.10 M, the fabricated ZnO NRs can densely distribute on the substrates; they have average diameters of 192 and 416 nm, and average lengths of 3.20 and 4.48 µm. Metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PDs) with interdigitated Au electrodes plated on top of the ZnO NR arrays were also evaluated. Under UV illumination of 370 nm and bias voltage of 3 V, the MSM UV PD based on ZnO NR arrays fabricated with the precursor concentration of 0.05 M has the largest photo-to-dark current contrast ratio of 47.28 among our samples, and its responsivity reaches 1.06´10-1 A/W, where the corresponding UV-to-Vis rejection ratio is 8.69.