Preparation and characterization of atomically clean, stoichiometric surfaces of AIN(0001)

In situ exposure of the (0001) surface of AlN thin films to flowing ammonia at 1120 °C and $10−4Torr$ removes oxygen∕hydroxide and hydrocarbon species below the detectable limits of x-ray photoelectron spectroscopy and decreases the Al∕N ratio from 1.3 to 1.0. The positions of the $Al2p$ and the $N1s$ core level peaks acquired from the cleaned surfaces were $75.0±0.1eV$ and $398.2±0.1eV$⁠, respectively, which were similar to the values determined for the as-loaded samples. The cleaning process left unchanged the $(1×1)$ low energy electron diffraction pattern, the step-and-terrace microstructure, and the root mean square roughness values observed for the surfaces of the as-loaded samples; i.e., the surface structure and microstructure were not changed by the high-temperature exposure to ammonia at low pressures. Vacuum annealing under $10−7Torr$ at 1175 °C for 15 min removed all detectable hydrocarbons; however, it did not remove the oxygen∕hydroxide species.