Defect Identification of Nitrogen-Doped Graphene on Pt (111) Using Atomic Force Microscopy and Scanning Tunneling Microscopy

Nitrogen (N)-doped graphene is a promising candidate for semiconducting devices and catalysts or sensor applications due to its controllable properties depending on the atomic structure of nitrogen defects. Therefore, it is important to control the doping configurations and understand the corresponding properties in order to utilize nitrogen-doped graphene for the applications. We investigated the nitrogen defects formed in graphene grown on the Pt(111) surface using pyridine precursors. In this study, we used scanning tunneling microscopy (STM) and atomic force microscopy (AFM) simultaneously to compare the atomic structures of defects with their electronic structures. We identified two different types of nitrogen defects: graphitic-N and pyridinic-N defects. Atomic resolution of AFM imaging confirmed the atomic arrangement of each defect, which was not clearly resolved in the STM imaging. In addition, the results of theoretical calculations using density functional theory were consistent with our experimental results and helped in identifying the defects. Moreover, we imaged the dissociated pyridine precursor prior to forming graphene, which provided insight into the growth mechanism and explained the density of nitrogen defects.