Determination of nitrogen-radical flux by nitridation of Al

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°C and an Al deposition rate of 0.1–2.0 Å/s. Without using the nitrogen radical beam source, AlN thin films were not synthesized. The nitridation ratio (NAl) was determined by electron probe micro analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). From the dependence of the NAl ratio on the deposition rate of Al, the maximum nitrogen radical flux was estimated to be 2.1 × 1014 radicals/cm2 · s. Although Al was completely nitrated no clear evidence of the crystalline phase of AlN was observed in X-ray diffraction (XRD).