GRAPHITE-LAYER FORMATION AT A DIAMOND (111) SURFACE STEP

Relaxation of a stepped (111) diamond surface is studied using an accurate, total-energy tight-binding method. We determined that the bare surface will become sp2 bonded near a step. This spontaneous graphitization is accompanied by a large increase in spacing between the surface layers. Band structures of the ideal and relaxed surfaces indicate that surface states are removed from the gap upon relaxation, but additional gap states arise from the lower layers. Addition of hydrogen to the surface will force the C atoms to revert back to sp3 bonding. These results are significant towards the understanding of the behavior of a stepped surface under conditions of film growth or even the possibility of diamond nucleation from graphite.