Visible light photoconductivity studies of gold nanoparticle embedded ZnO thin films for photo detector application

This report demonstrates the visible photo response of gold nanoparticles (AuNPs) embedded ZnO nanocomposite (AuNPs-ZnO) thin films. The AuNPs-ZnO films were prepared by sandwiching DC sputtered AuNPs in between two RF sputtered ZnO layers deposited on p-Si. Crystal phase purity and surface morphology were characterized by the x-ray diffraction and scanning electron microscope. The formation of AuNPs was confirmed by observing the plasmonic dip in optical transmittance. Photoconductivity study was done by recording current-voltage characteristics of the films in the presence of visible light. The ratio of light to dark current was found to be enhanced by two to three orders of magnitude with the inclusion of AuNPs. The observed photocurrent enhancement was found to vary with both AuNPs concentration and sandwich thickness. The highest responsivity observed with the fabricated nanocomposite films was of 0.012 A W-1. The dominant reason for the visible photoconductivity and for the enhancement in photocurrent was ascribed to the plasmonic properties of AuNPs-ZnO composite film. This study paves a new approach to design and fabricate devices for optoelectronic applications.