Ultrasensitive zinc magnesium oxide nanorods based micro-sensor platform for UV detection and light trapping

Abstract

A cost effective unique approach has been employed to realize high quality zinc magnesium oxide (Zn1-xMgxO) based nanostructures which can replace conventional material i.e. Zinc oxide (ZnO) in detector and sensor applications. High resolution structural studies showed the formation of vertically aligned hexagonal and truncated hexagonal nanorods on RF sputtered ZnO and Zn1-xMgxO seed layer. Single crystal Zn1-xMgxO and ZnO nanorods with dominant c-axis growth along (002) crystal axis and d-spacing of 0.262 and 0.266 nm, respectively were obtained from high resolution transmission electron microscopy, selective area diffraction pattern and high resolution X-ray diffraction spectra. The high external quantum efficiency of 12.054% with narrow full width half maxima of 12.63 nm was achieved from photoluminescence spectroscopy (Zn1-xMgxO nanorods) performed at room temperature. Approximately two order of enhancement in current density was observed from photodetector fabricated using Zn1-xMgxO nanorods. A state of art peak responsivity of 62.19 A/W at 350 nm attributed to near band edge emission peak and high current rectification capability with a maximum internal gain of 185 was measured from Zn1-xMgxO detector. Zn1-xMgxO detector exhibited temporal response with reasonable rise and fall time constants along with three order higher detectivity values in comparison to ZnO detector. A DC current based humidity sensor was fabricated and characterized using sample synthesized for longer growth duration. High sensitivity of 1.612 /% RH was achieved and low recovery time was observed as the sample was subjected to annealing treatment.