Sample resistance change due to temperature variation around room temperature. The left graph shows a metallic response from samples 3 and 4 (monolayer GR device). The right graph shows a semiconductor response from sample 2 (bilayer GR device). The two devices shown as insets are implemented using the mask patterns of Figure 1a. They are identical except for the graphene thickness.
Mahjoub et al. Nanoscale Research Letters 2013 8:22 doi:10.1186/1556-276X-8-22