Revista de Ciências e Engenharia de Materiais

Process of Diamond Surface Termination by Carboxylic and Amino Groups: A Quantum Mechanics Approach

Abstract

Yuan Tian and Karin Larsson

The main goal with the present work has been to study the possibility and thermodynamic stability for a sequential termination with either carboxylic groups (COOH), or amino groups (NH₂), from an initially H-terminated diamond (111) or 100)-2x1 surface. It was shown that it is energetically preferable to terminate both types of surfaces with up to 50% with COOH species. Moreover, it was shown possible to terminate both types of surface with up to 100% coverage with NH₂ species. In order to follow bond energy variations with variations in surface coverage, the averaged adsorption energies were also calculated. As expected, the lowest COOH coverage (of 6.25 %) resulted in the energetically most preferable adsorption energies. The situation with the NH₂ group was identical for the diamond (111) surface, with the lowest surface coverage (of 6.25%) leading to the most preferable adsorption situation. For the situation with diamond (100)-2x1, the preferable adsorption situation was for a surface coverage of 43.75% NH₂ species.

Partial Density of States (pDOS´s) were also calculated with the purpose to analyse the adsorbate-induced surface electronic properties. COOH-terminated diamond (100)-2x1 surface, as well as COOH- and NH₂-terminated diamond (111) surfaces, where shown to display surface conductivities which were not observed for 100% H-terminated surfaces.