Surface oxygen artifacts on aluminum nitride

Aluminum nitride (AlN)is an increasingly important electronic ceramic with oxygen as an important bulk impurity. Quantitative microanalysis of oxygen to determine its precise distribution is a necessary step in characterization of the ceramic that may be complicated due to surface oxidation. AlN is thermodynamically unstable compared to the oxide (Al 2 O 3 ) at room temperature in the presence of environmental oxygen or water and may thus be expected to form a thin, possibly passive oxide film similar to the oxide layer of pure aluminum metal. Such an oxide layer has been used to explain anomalies in oxygen quantification in AlN by neutron activation methods [1] but reflecteion high energy electron diffraction studies [2] failed to reveal either crystalline or amorphous oxide phases forming at room temperature. Electron diffraction techniques in the transmission electron microscope were used to examine thin AlN sections for possiblecrystalline surface layers. A ceramic AlN sample was prepared using conventional techniques for the preparation of thin foils with final thinning accomplished by ion milling.