▎ 摘　　要

We report photoresponse measurements from two comparable epitaxial graphene (EG) devices of different thicknesses (2-layer vs. similar to 10-layer EG) made on SiC substrates. An asymmetric metal contact scheme was used in a planar configuration to form a Ti/EG/Pd junction. By moving the laser illumination across the junction, we observed an increased photocurrent signal resulting from local enhancement of electric field near the metal/EG contact. A maximum photoresponsivity of 1.11mA/W without bias was achieved at the Pd/EG contact in the 10-layer EG device. Photocurrent was also observed under AM 1.5 illumination. Our experiments demonstrate the high tunability of this EG photodetector by varying EG thickness, metal leads, channel length, and/or illumination area. (C) 2013 AIP Publishing LLC.