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Inversion Domain Boundaries and Oxygen Accommodation in Aluminum Nitride
Published online by Cambridge University Press: 21 February 2011
Abstract
Aluminum nitride is known to have a large affinity for oxygen as an impurity. At high levels (>∼4 wt/o) the oxygen is incorporated in the form of planar stacking faults where “pure” 2H AIN is regularly interspersed with a layer of oxygen at the faults. At oxygen levels lower than ∼ 4 wt/o the structure shows an expanded c-axis. The present authors have not observed this effect, rather a random distribution of stacking faults is observed along with another, more prevalent, extended defect identified as an inversion domain boundary (IDB). The IDBs are significantly aplanar (indicating a low interface energy), and often have precipitates and other, faceted defects associated with them. The role of these defects in oxygen accommodation in AIN has been investigated both structurally and chemically by electron optical methods (SEM, TEM, STEM, HREM, CBED, EDS, EELS, and CL-TEM). The structural nature of the boundaries, in the absence of oxygen, requires Al-Al or N-N bonding to occur with some frequency across the boundary. Such bonding is unlikely due to the excess energy required. Chemical analysis (EELS) and luminescence studies (CL-TEM) reveal that oxygen is often associated with the boundaries and may mediate the bonding at the boundary. A model is proposed for the IDB which includes structural aspects combined with considerations of stoichiometry in an effort to understand the origin and energetics of this defect.
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- Copyright © Materials Research Society 1990
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