Received: October 2, 2007

In Final Form: December 4, 2007

Abstract:

Diamond surface susceptibility toward the degree and type of termination and reconstruction has been investigated theoretically by using density functional theory methods. The adsorption geometries and energies for H, O, and OH species adsorbed to diamond (111)-1 × 1 and (111)-2 × 1 surfaces under varying surface coverage were studied and compared with corresponding processes on the diamond (100)-2 × 1 surface. Furthermore, the energy barrier for the diamond (111)-1 × 1 to (111)-2 × 1 surface reconstruction for non-, H-, and O-terminated surfaces were also investigated using first-principle synchrotron transit methodologies. The results show that the adsorption energies for H, O, and OH are -4.53, -5.28, and -4.15 eV, respectively, for 100% terminated diamond (111)-1 × 1 surfaces and -3.29, -3.82, and -2.77 eV, respectively, for the diamond (111)-2 × 1 surfaces. Adsorption of O was found to be most energetically favorable in the on-top position on the 1 × 1 surface and in the bridge position on the 2 × 1 surface. The OH groups showed less-favorable adsorption energies in comparison to H and O. The calculations also show that the 1 × 1 surface configuration is energetically stable against transformation to the 2 × 1 configuration (of type Pandey chain) with a correspondingly small energy barrier; 0.32 eV. For this specific direction of surface reconstruction, significantly higher barriers were found for the H- and O-terminated diamond surfaces (58.4 and 44.0 eV, respectively). Plausible explanations for these observations are that the surface C-H and C-O bonds must be disrupted for the 2 × 1 (Pandey chain) reconstruction to occur.

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