Authors: J. Loomis, B. Panchapakesan
Affilation: University of Louisville, United States
Pages: 33 - 36
Keywords: graphene, reduced graphene oxide, photocurrent
In this paper, we report large photocurrents in air-assisted depositions of reduced graphene films (derived from reduced single layer graphene oxide) upon illumination with near-infrared (NIR) light. NIR-induced charge carrier generation and subsequent separation at the metal–graphene interface resulted in photocurrent generation. Varying bias voltages were applied to test samples and allowed for evaluating photoresponses in either diffusion- or drift-dominated regions. In the diffusion-dominated region, position-dependent effects of photoconductivity were demonstrated. The photocurrent exhibited increase when the positive electrode was illuminated, decrease when the negative electrode was illuminated, and negligible response when the area between the electrodes was illuminated. The percent change in current from 150% (40 mW NIR) to 1800% (335 mW NIR) is reported. Such large photocurrent responses result from built-in electric fields and optically generated temperature gradients (maximum NIR-induced temperature rise 70 C). In the drift-dominated realm, a Gaussian photocurrent profile was obtained, signaling drift of charge carriers with increase in localized electric field, demonstrating the classic Haynes–Shockley experiment in reduced graphene films. A minority carrier mobility value of ~700 cm2/V-s is reported. The simple low cost graphene devices presented in this paper were fabricated without lithographic processing and are ideal candidates for assorted infrared imaging applications.