Dissociative adsorption of ammonia on the ZrB2(0001) surface

Zirconium diboride has been proposed as a viable substrate for epitaxial growth of group III nitrides. In many methods of nitride growth on ZrB2 surfaces, ammonia gas is the nitrogen source. Here we use X-ray photoelectron spectroscopy at a series of fixed temperatures from room temperature to 535 °C and density functional theory to study the dissociative adsorption of ammonia on the ZrB2(0001) surface. A significant increase is observed between ~ 250 and ~ 400 °C for the deposition of nitrogen, which can be desorbed by annealing between 950 and 1150 °C. Two components of the N 1s peak are observed and are associated with bonding of nitrogen to boron or to zirconium. Comparison of spectra obtained at two different emission angles suggests that more N is bonded to B than to Zr at the surface and when boron is bonded to nitrogen, it migrates towards the surface. This may be a factor in limiting group III nitride epitaxial growth on the ZrB2(0001) surface.