Optoelectronic properties of optimally grown ZnO nanorods

Simple yet most reproducible method of dense, well-aligned, oriented and high crystalline quality zinc oxide nanorods (ZnO-NRs) is systematically investigated. c-axis oriented, hexagonal ZnO-NRs growth process by using chemical bath deposition (CBD) at different growth temperature was optimized to study their optoelectronic properties. The surface densities of ZnO-NRs were found to be controlled by the growth temperatures. Single wurtzite phase of seed layer and vertically grown ZnO-NRs were confirmed by X-Ray diffraction (XRD). Field emission scanning electron microscopy (FE-SEM) showed varying density of NRs grown at 60 degrees C, 75 degrees C, and 95 degrees, while the lengths were found to have less effect of growth temperatures. The crystallite uniformity and surface morphology from atomic force microscopy (AFM) suggested smooth surfaces with RMS roughness below 34 nm for all samples. The optical band gaps determined from UV-Vis transmittance and absorption spectra showed a decrease in the ZnO band gap from 3.29 to 3.19 eV, while the lower number of bound-exciton peaks in the photoluminescence (PL) spectroscopy were attributed to the optimally grown ZnO-NRs. Carrier concentration and mobilities estimated by Hall effect measurements showed improved values for optimally grown sample. High photocurrent values for the ZnO-NRs grown at 75 degrees C showed superior performance under UV illuminations; however, dark and ambient light exposure exhibited less effects on photocurrents for all the samples. Dynamic photoresponse with the UV exposures of ZnO seed and nanorods revealed an interesting current switching behavior up to prolonged time without any significant degradation. Combined optical and electrical results indicate that the CBD-grown ZnO-NRs were highly photosensitive and promising for the optoelectronic and UV photo-detector application.

Automated summary

A simple and reproducible method for producing high-quality zinc oxide nanorods (ZnO-NRs) was investigated. The growth process of hexagonal ZnO-NRs with c-axis orientation was optimized to study their optoelectronic properties. The results show that the growth temperature controls the surface density of ZnO-NRs, while the length is less affected. The ZnO-NRs exhibit high photosensitivity and have potential applications in optoelectronics and UV photo-detectors.