Oxidation of Aluminum Nitride for Defect Characterization

Abstract

The thermal oxidation of aluminum nitride was developed as a means to study defects in bulk aluminum nitride crystals. The oxidation kinetics was established for the dry oxidation of highly textured AlN polycrystals produced by sublimation-recombination crystal growth in a tungsten furnace. Despite seeding on polycrystalline tungsten, the grains were predominantly [0001] oriented as verified by electron backscattering diffraction (EBSD). The oxidation rate is dependent on the crystal’s orientation, polarity, stress, and surface condition, thus oxidation decorates grain boundaries, polishing scratches, and inversion domains by producing oxide layers of different thicknesses. The initial oxidation rate of nitrogen polar (0001) AlN is approximately 25% faster than on aluminum polar crystals. Low temperature (800 °C) dry oxidation produced an amorphous oxide layer and generated a high density of defects (vacancies, stacking faults, and dislocations) in the nitride near the oxide/nitride interface, as observed by cross-sectional transmission electron microscopy. In contrast, high temperature oxidation (1000 °C) produced a crystalline oxide layer, and left the nitride free of observable defects.

AlN hollow-nanofilaments by electrospinning

“…Compared to the literature, these results confirm a high stability of the AlN NFs against oxidation up to around 550 °C. These AlN NFs seem to be, under oxidative atmosphere, at least as good as AlN materials previously investigated in the literature with other dimensions (micropowders [36], films [37], bulk [38]) . This result is very important taking into account the maximum working temperature of about 300-400 °C, before implying the polymer degradation (most commonly polyimide or epoxy resins).…”