Decomposition of NH$_{3}$ and H$_{2}$ on ZrB$_{2}$ (0001) surface

Group III nitride semiconductors (AlN, GaN, InN, and their alloys) are important materials for applications in solid-state lighting, optoelectronics, and photovoltaics. However, the lack of lattice--matched substrates for their growth results in less than optimal material quality. In the last decade, zirconium diboride (ZrB$_{2})$ has been demonstrated as a promising substrate for GaN growth because of its similar lattice constant and thermal expansion properties when compared to the nitride. Moreover, the high electrical conductivity of ZrB$_{2}$ makes it desirable for many GaN-based device applications. In this talk, we present results of density functional theory calculations for the reactivity of the ZrB$_{2}$(0001) surface towards the N precursor, NH$_{3}$, and the carrier gas, H$_{2}$, commonly used in metal organic chemical vapor deposition and molecular beam epitaxy of nitrides. Two different terminations of ZrB$_{2}$(0001) surface, the Zr and B terminations, are considered and assessed in terms of their catalytic properties toward NH$_{3}$ and H$_{2}$ decomposition. The theoretical results are analyzed in connection with our recent XPS and RAIRS measurements.