C-terminated reconstruction and C-chain structure on Mo2C(0001) surface studied by low energy electron diffraction and scanning tunneling microscopy

The structure of an alpha-Mo2C(0001) surface varies depending on the anneal ing temperature. At least three phases are observed by low energy electron diffraction (LEED). A well-ordered (root 3 x root 3)R30 degrees structure w as observed on alpha-Mo2C(0001) at annealing temperatures below 960 K, whic h was imaged as a honeycomb structure by scanning tunneling microscopy (STM ). A model was proposed for the C-terminated structure where C atoms are lo cated 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 (root 3 x root 3)R30 degrees structure to a c(2x4) structure where zigzag rows running parallel tb each other were observed by STM.