Low Dark Current and High Responsivity UV Detector Based on TiO2 Nanowire/RGO Thin Film Heterostructure

Abstract

A UV detector was fabricated using glancing angle deposition (GLAD)-synthesized TiO2 nanowires (NWs) over spin-coated reduced graphene oxide (RGO) thin films (TFs) on a Si substrate. The field-emission scanning electron microscopy (FE-SEM) images showed that TiO2 NWs were grown with a length of ~140 nm. The fabricated TiO2 NWs were amorphous in nature, as depicted by the selected area electron diffraction (SAED) pattern which was also verified by X-ray diffraction (XRD) analysis. On average, ninefold enhanced optical absorption was observed for the TiO2 NW/RGO TF/Si sample compared to the bare TiO2 NW/Si sample. A significantly low dark current of 2.9 nA (at +1 V) was obtained after the incorporation of the RGO TF beneath the TiO2 NWs. The fabricated Au/TiO2 NW/RGO TF/Si device showed high responsivity and detectivity of 75.7 A/W and ${6.86} \times {10}^{{13}}$ Jones, respectively, under 380-nm light illumination having a power density of as low as $0.8~\mu \text{W}$ /cm2. A low noise-equivalent power (NEP) of 49 fW was also obtained from the resulting detector. The rise and fall times of the Au/TiO2 NW/RGO TF/Si detector were 0.8 and 1.09 s, respectively.