Effect of Ag decoration on the photodetection of catalyst-free synthesized vertically oriented SiOx NW arrays

Abstract

This study reports a catalyst-free synthesis of silver (Ag) nanoparticles (NPs) decorated SiOx nanowire (NW) arrays on silicon (Si) substrates by employing the GLAD technique. A huge enhancement in optical absorption was seen all over the visible spectrum as compared to bare SiOx NW arrays. Photoluminescence measurement showed many defect-related emissions in the UV-vis region. The successful growth of vertically oriented Ag decorated SiOx NWs on Si substrate was manifested through the field emission gun scanning electron microscopy (FEGSEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The transmission electron microscope analysis revealed the crystalline and amorphous nature of Ag NPs and SiOx NWs respectively. Through Tauc plot, a low bandgap of 1.9 eV was obtained after decorating the bare SiOx NWs with Ag NPs. The device successfully exhibited properties of Schottky diode through its rectifying behaviour. Most interestingly, very low turn-on voltages of 1.4 V and 1.8 V were obtained for Ag decorated SiOx NWs corresponding to the white light and dark conditions as compared to bare SiOx NWs whose turn–on voltages were 1.8 V and 2.8 V respectively. The Ag decorated SiOx NW detector gave a low ideality factor of only 10.27 as compared to 20.99 for bare SiOx NW detector. At −5 V, the device showed a responsivity of 1.54 A/W, detectivity of 2.12 × 1010 Jones and EQE of 5.17 × 102 %. Moreover, seven-fold enhancement of photocurrent to dark current contrast ratio was obtained for the Ag decorated SiOx NW device at -0.2 V accompanied with a fast response of 0.12 s (rise time) and 0.11 s (fall time), thus expanding its usability.