The environment of graphene probed by electrostatic force microscopy

3 pages, 3 figures.-- PACS nrs.: 72.80.Rj, 82.65.+r.-- ArXiv pre-print available at: http://arxiv.org/abs/0803.2032We employ electrostatic force microscopy to study the electrostatic environment of graphene sheets prepared with the micromechanical exfoliation technique. We detect the electric dipole of residues left from the adhesive tape during graphene preparation, as well as the dipole of water molecules adsorbed on top of graphene. Water molecules form a dipole layer that can generate an electric field as large as ~10^9 V m−1. We expect that water molecules can significantly modify the electrical properties of graphene devices.This work was supported by an EURYI grant, FP6-IST-021285-2 and EXPLORA NAN2007–29375–E, Ministerio de Educación y Ciencia, Spain. D.J. acknowledges financial support from Ministerio de Educación y Ciencia under project TEC2006–13731–C0201/MIC.Peer reviewe