  Nitrogen-vacancy (NV) centers in diamond have attracted a great deal of
attention because of their possible use in information processing and
electromagnetic sensing technologies. We examined theatomistic generation
mechanism for the NV defect aligned in the [111] direction of C(111)
substrates. We found that N is incorporated in the C bilayers during the
lateral growth arising from a sequence of kink propagation along the step edge
down to [-1,-1,2]. As a result, the atomic configuration with the N-atom
lone-pair pointing in the [111] direction is formed, which causes preferential
alignment of NVs. Our model is consistent with recent experimental data for
perfect NV alignment in C(111) substrates.
