Imaging charge density fluctuations in graphene using Coulomb blockade spectroscopy

A. Deshpande, W. Bao, H. Zhang, Z. Zhao, C. N. Lau, B. J. LeRoy

Published 2010-12-02, updated 2010-12-03Version 2

Using scanning tunneling microscopy, we have imaged local charge density fluctuations in monolayer graphene. By placing a small gold nanoparticle on the end of the STM tip, a charge sensor is created. By raster scanning the tip over the surface and using Coulomb blockade spectroscopy, we map the local charge on the graphene. We observe a series of electron and hole doped puddles with a characteristic length scale of about 20 nm. Theoretical calculations for the correlation length of the puddles based on the number of impurities are in agreement with our measurements.