Novel selective etching reaction of carbon atoms on molybdenum carbide by oxygen at room temperature visualized by scanning tunneling microscopy

We have succeeded in imaging each surface carbon atom on Mo2C(0001) by scanning tunneling microscopy operated at low tunneling resistances and found a novel selective etching reaction of the surface carbon atoms by oxygen gas exposed at room temperature. On a carbon terminated Mo2C(0001) surface with both (√3×√3)R30°-honeycomb and c(2×4)-zigzag row structures, the etching reaction selectively occurred on the c(2×4)-zigzag row structure, leading to exposure of the underlying (1×1) Mo layer. Energetically excited oxygen formed on the surface is probably responsible for this new reaction event.