▎ 摘　　要

We report the contact potential difference and work function variation among graphene-based derivatives, such as graphene oxide, reduced graphene oxide and pristine graphene, analyzed by Kelvin probe force microscopy in ambient conditions. The work function is strongly dependent on the amount of oxygen-containing functional groups, moisture or other adsorbates present on the material, and also on the environmental factors. With the removal of oxygen-containing functional groups, during reduction of graphene oxide, the work function decreases, indicating that the electrical properties of graphene oxide has changed. Moreover, we demonstrate that the lattice defect restoration in graphene oxide during thermal reduction results in reduced graphene oxide sheets with a work function of 4.44 eV, which is in the range of reported values for pristine graphene. (C) 2020 The Japan Society of Applied Physics.