Abstract
Chemical kinetics of a two-dimensional (2D) AlN layer formation on the (0001) sapphire (Al2O3) surface during nitridation as function of ammonia flux and temperature is investigated by reflection high-energy electron diffraction. The process on the surface is described in framework of a chemical reactions kinetic model including interaction between partially reduced aluminum oxide species (AlO) and chemisorbed NH2 particles for the temperature range 1210 K. In this range, the process is described as a phase transition in frame of lattice gas model. Precision measurement of 2D AlN lattice parameters during the nitridation process detects the value of 0.301 nm. This value strongly differs from bulk value of wurtzite AlN structure 0.311 nm, but it coincides exactly with a characteristic structure parameter of the oxygen-deficient (0001) Al2O3 surface with reconstruction (√31×√31)R ± 9°. We assume that this coincidence is the result of minimizing the elastic stresses at the heterojunction of the 2D AlN and the (0001) Al2O3 layer.
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