S. Watanabe and H. Nozoye
[Appl. Surf. Sci., Vol.113/114, pp.618-621, 1997]

AlN thin films were synthesized on MgO substrates by means of direct nitridation of Al with a newly designed nitrogen-radical beam radio-frequency source while Al was evaporated at a substrate temperature of 380-550Ž and an Al deposition rate of 0.1-2.0 π/s. Without using the nitrogen radical beam source, AlN thin films were not synthesized. The nitridation ratio (N/Al) was determined by electron probe micro analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). From the dependence of the N/Al ratio on the deposition rate of Al, the maximum nitrogen radical flux was estimated to be 2.1~10¹⁴ radicals/cm²Es. Although Al was completely nitrated, no clear evidence of the crystalline phase of AlN was observed in X-ray diffraction (XRD).