▎ 摘　　要

We have investigated shot noise at microwave frequencies in wide-aspect-ratio graphene sheets in the temperature range of 4.2-30 K. We find that for our short (L < 300 nm) graphene samples with width over length ratio W/L > 3, the Fano factor f reaches a maximum f similar to 1/3 at the Dirac point and that it decreases substantially with increasing charge density. Our results agree with the theoretical prediction that electrical transport at the Dirac point is governed by evanescent electronic states. (C) 2009 Elsevier Ltd. All rights reserved.