Figure 2.

Scanning photocurrent (SPC) measurements of the diode at various reverse biases. (a) Optical micrograph of the diode. The area inside the red rectangle was scanned for photocurrent measurements. The graphene region is represented by the black dashed rectangle. The horizontal yellow dashed lines inside the scanned area depict the SiO₂ region and the same is valid for all the images. Photocurrent maps of the scanned area at a laser power of 2 μW and a reverse bias of (b) −1, (c) −1.5, and (d) −2 V. (e) Evolution of the photocurrent (shown as absolute values) with increase in reverse voltage in G/Si (circle symbol) and G/SiO₂ (rectangle symbol) regions at a laser power of 2 μW. A higher current is observed in G/SiO₂ region compared to G/Si region at reverse biases slightly above 1 V.