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

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Abstract
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.

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