Structure of the diamond (111) surface: Single-dangling-bond versus triple-dangling-bond face

Abstract

We present converged first-principles calculations for the atomic and electronic structure of diamond (111) surfaces based on density-functional theory in the local-density approximation. Single- and triple-dangling- bond surfaces with 1\ifmmode\times\else\texttimes\fi{}1, 2\ifmmode\times\else\texttimes\fi{}1, and ($\sqrt{3}$\ifmmode\times\else\texttimes\fi{}$\sqrt{3}$)R30\ifmmode^\circ\else\textdegree\fi{} translational symmetry are studied by means of total-energy minimizations. The ground-state geometries and electronic band structures are computed. In contrast to earlier work we find the \ensuremath{\pi}-bonded chains to be nearly undimerized and unbuckled in the 2\ifmmode\times\else\texttimes\fi{}1 Pandey reconstruction. Consequently, the electronic band structure exhibits no optical gap. Other structures are higher in total energy (\ensuremath{\pi}-bonded molecule model, relaxed truncated-bulk structure) or represent only saddle points at the Born-Oppenheimer energy surface (graphitelike surface, strongly dimerized chains). Chain and trimer reconstructions at the triple-dangling-bond C(111) surface are very close in energy and domains of different reconstructions can compete. These structures may explain recent scanning tunneling microscopy findings on films grown by chemical vapor deposition. \textcopyright{} 1996 The American Physical Society.