Growth of thin Ni films on GaN(0001)-(1×1)

The growth and structure of Ni films, formed by in situ deposition on atomically clean GaN(0001)-(1×{}1) surfaces, have been studied using Auger, electron-energy-loss, and ultraviolet-photoemission spectroscopies, and low-energy electron diffraction. Near room temperature, a disordered film grows in a continuous, layer-by-layer mode. Annealing a thin layer at {~}700--800 ^∘{}C forms ordered Ni islands in registry with the GaN. The resulting Ni(111)-(1×{}1) surface then induces ordering during subsequent deposition of thicker Ni layers near room temperature. Chemical reaction at the interface occurs even near room temperature. The N released appears near the Ni surface, while the free Ga remains near the interface. Annealing at T{≥}600 ^∘{}C leads to the loss of N by desorption and to extensive intermixing of Ga and Ni. Depending on annealing temperature, Ga-induced ({}3 ×{} {}3 )R30^∘{} or (2×{}2) superstructures are observed on the Ni(111) surface. A Ga metal film deposited on the Ni layer is able to combine with some of the N, escaping during high-temperature annealing, to reform a poorly ordered GaN phase.