Local bonding behavior and domain size relation for vacancy lines on Si(001)

Using a highly accurate tight-binding total-energy approach applied to large supercells, we have studied the local bonding behavior and the domain size relation for vacancy lines (VL’s) on Si(001) over a wide range of surface dimer vacancy density Θ. For VL’s perpendicular to surface dimer rows, strong local bonding interactions exist at the VL edges and between neighboring VL’s. Delicate balance between strain release and rebonding leads to sensitive dependence of local bonding configurations on Θ. On the other hand, for VL’s parallel to surface dimer rows all excessive dangling bonds rebond, leading to much weaker interactions between VL’s and a distribution pattern drastically different from that of perpendicular VL’s. Further examination of the VL domain size relation reveals an effective long-range interaction decaying as 1/r² for perpendicular VL’s, but not for parallel VL’s.