C-Terminated Reconstruction and C-Chain Structure on Mo2C(0001) Surface Studied by Low Energy Electron Diffraction and Scanning Tunneling Microscopy

Abstract
The structure of an α-Mo2C(0001) surface varies depending on the annealing temperature. At least three phases are observed by low energy electron diffraction (LEED). A well-ordered (√3×√3)R30° structure was observed on α-Mo2C(0001) at annealing temperatures below 960 K, which was imaged as a honeycomb structure by scanning tunneling microscopy (STM). A model was proposed for the C-terminated structure where C atoms are located on the threefold hollow sites of a Mo layer, and each carbon atom is observed as a depression of the honeycomb structure by STM. An increase in carbon coverage on the surface transformed the (√3×√3)R30° structure to a c(2×4) structure where zigzag rows running parallel to each other were observed by STM.