The role of Zn vacancies in UV sensing with ZnO nanorods

The UV sensing properties of ZnO nanorods (NRs) fabricated by a chemical bath deposition using two different hexamethylenetetramine (HMTA) concentrations, 25mM and 50 mM, are studied in this work. The NRs are investigated by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and photoconductivity measurements. The SEM images indicate that 25mM HMTA NRs exhibit merging that increases the growth induced defects in this sample with respect to the 50mM sample. PL measurements demonstrate a higher optical transition from the doubly ionized Zn vacancy (V-Zn(2-)) at 2.52 eV in the 50mM ZnO NRs due to the reduced growth defect density. The photoconductivity measurements indicate better sensitivity and spectral selectivity in the 50mM NRs, which we present as a result of the V-Zn(2-) state. These results are summarised with a UV sensing model based on the optical properties of ZnO NRs, which provides a route for the development of improved sensors. Published by AIP Publishing.