OXIDATION OF SINTERED ALUMINUM NITRIDE AT NEAR-AMBIENT TEMPERATURES

Oxidation of sintered aluminum nitride at low temperatures (20-degrees-200-degrees-C) was studied using transmission electron microscopy (TEM). Particles of alpha-Al2O3, about 20-30 angstrom in size, were found to form within minutes on freshly cleaned surfaces of AlN at room temperature. The oxide was found to grow nearly epitaxially on AlN when the {0001}AlN planes were exposed to the surface. Limited nonepitaxial oxidation was also observed when the basal planes were inclined to the TEM foil surface. After 10 h in air at 75-degrees-C, the particles coarsened to about 50 angstrom while after 150 h at 200-degrees-C, an oxide film, about 500 angstrom thick, was observed on some grains.