Highly sensitive UVA and violet photodetector based on single-layer graphene-TiO2 heterojunction.

ABSTRACT

A highly sensitive ultraviolet A (UVA) and violet photodetector based on p-type single-layer graphene (SLG)-TiO2 heterostructure was fabricated by transferring chemical vapor deposition derived SLG on the surface of commercial single-crystal TiO2 wafer. Optoelectronic analysis reveals the as-fabricated Schottky junction PD was highly sensitive to light illumination in UVA and violet range, with peak sensitivity at 410 nm and excellent stability and reproducibility, but virtually blind to illumination with wavelength less than 350 nm or more than 460 nm. The on/off ratio of the device was calculated to be 6.8 × 104, which is better than the majority of previously reported TiO2 based PDs. What is more, the rise/fall time were estimated to be 0.74/1.18 ms, much faster than other TiO2 based counterparts. The totality of the above result signifies that the present SLG-TiO2 Schottky junction photodetector may have promising application in future high-speed, high-sensitivity optoelectronic nanodevices and systems.