Adsorbate Formation/Removal and Plasma‐Induced Evolution of Defects in Graphitic Materials

Abstract

AbstractThe preparation of adsorbate‐free graphene with well‐defined layer numbers is a current challenge in materials and surface science and required to fabricate graphene‐based nanodevices, such as used in nanoelectromechanical systems. One strategy to tailor the layer number is oxygen‐plasma treatment of few‐layer graphene/graphite flakes. However, when graphitic materials are stored in air under ambient conditions, it is almost inevitable that adsorbates deposit on their surfaces. When precisely removing individual graphene layers from graphitic flakes by oxygen‐plasma treatment, the amount and type of adsorbates strongly affect the required plasma‐treatment process and duration. To examine the removal/etching mechanism involved in removing such layers, few‐layer graphene/graphite flakes, with areas of different layer numbers, are stored in ambient air and stepwise exposed to oxygen plasma in a shielded configuration. The flakes are then successively analyzed by multifrequency atomic force microscopy together with Raman spectroscopy, focusing on etching rate, and adsorbate and defect evolution. Combined in‐plane and out‐of‐plane tip–adsorbate–substrate interaction analysis facilitates discrimination of different types of adsorbates (water, polycyclic aromatic hydrocarbons, and linear alkanes) and their formation with time. The results demonstrate the potential regarding the development of an efficient method for cleaning of graphitic surfaces and ablation of individual graphene layers.