Adsorption Characteristics of Boron and Nitrogen on 3x3 Reconstructed Surface of 6H-SiC

Regarding the subject of hexagonal boron nitride (<i>h</i>-BN) film growth on dielectric substrate, elemental adsorptions of boron and nitrogen on silicon carbide(SiC) are studied using density functional theory. Among various SiC surface reconstructions stable at temperature lower than that of thermal decomposition and spontaneous graphitization, the choice of substrate is made to be the 3X3 reconstructed 6H-SiC (0001), which is the least reactive with a twisted layer of Si ad-atoms featuring a single dangling bond. The analysis on trajectory ensemble of 1152 adsorptions, spanning the whole surface, reveals all adsorption sites available for B and N on 6H-SiC (0001) 3X3 surface. We found that those multitudes of adsorption sites can be grouped into three regions surrounding three non-twisted silicon ad-atoms on the surface. Adsorption sites with the highest adsorption energies are found to be identical for B and N, however, with distinguishable configurations. The capture ratio relating to the initial population of each adsorption site is found to be governed by the surface configuration, being the highest near the extruded Si ad-atom, but weakly correlated to the adsorption energy of the corresponding site.<br/>Study of elemental adsorption on substrate can be directly associated with MBE process using elemental flux toward substrate. Even in MOCVD or ALD process, elemental adsorption characteristics indirectly contribute to the overall understanding of the growth process, as surface reactions involving precursor compounds often result in elements adsorbed on the surface.