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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs were grown with a length of ~140 nm. The fabricated TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW/RGO TF/Si sample compared to the bare TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NWs. The fabricated Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW/RGO TF/Si device showed high responsivity and detectivity of 75.7 A/W and 6.86 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> Jones, respectively, under 380-nm light illumination having a power density of as low as 0.8 μW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A low noise-equivalent power (NEP) of 49 fW was also obtained from the resulting detector. The rise and fall times of the Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW/RGO TF/Si detector were 0.8 and 1.09 s, respectively.