Modification of the Surface Structure and Electronic Properties of Diamond (100) with Tin as a Surface Termination: A Density Functional Theory Study

Many metal and metal oxide terminations have resulted in imparting negative electron affinity (NEA) to various diamond surfaces, especially diamond (100), and lowering the surface work function considerably. Tin, having many interesting properties in both metallic and oxide forms and being nontoxic and abundant, has the potential of being an efficient termination of diamond for interesting surface properties. Density functional theory is used to assess tin adsorption on the bare and oxygen-terminated diamond (100) surface. Quarter and half monolayer coverages of tin were found to be the most stable coverages in the case of both bare and oxygen-terminated diamond, resulting in large adsorption energies (up to −6.5 eV on the oxygen-terminated surface with an electron affinity up to −1.5 eV), comparable to the results obtained for H-terminated and alkali metal/metal oxide-terminated diamond surfaces. The electrostatic potential and density of states calculations suggest a stronger covalent bonding between the surface species along with the shift in the electron density toward or in the vicinity of surface carbon atoms, which leads to NEA. These results lay a foundation for any future investigation into this novel termination.