Using the recently developed technique of microsoldering, we perform a systematic transport study of the influence of PMMA on graphene flakes revealing a doping effect of up to 3.8x10^12 1/cm^2, but a negligible influence on mobility and gate voltage induced hysteresis. Moreover, we show that the microsoldered graphene is free of contamination and exhibits a very similar intrinsic rippling as has been found for lithographically contacted flakes. Finally, we demonstrate a current induced closing of the previously found phonon gap appearing in scanning tunneling spectroscopy experiments, strongly non-linear features at higher bias probably caused by vibrations of the flake and a B-field induced double peak attributed to the 0.Landau level of graphene.
@article{arxiv.0912.2218,
title = {Electrical transport and low-temperature scanning tunneling microscopy of microsoldered graphene},
author = {V. Geringer and D. Subramaniam and A. K. Michel and B. Szafranek and D. Schall and A. Georgi and T. Mashoff and D. Neumaier and M. Liebmann and M. Morgenstern},
journal= {arXiv preprint arXiv:0912.2218},
year = {2010}
}