Analysis of Broken Symmetry in Convergent-Beam Electron Diffraction along and Zone-Axes of AlN for Polarity Determination

Abstract

To accurately and easily determine the polarity of AlN using transmission electron microscopy, we compare the convergent-beam electron diffraction (CBED) patterns along the widely used <112̄0 > and <11̄00 > zone-axes. For the <112̄0 > zone-axis, the diffraction disk of g= 0002 differs from that of g= 0002̄, while for <11̄00 >, the diffraction disks of g= 0002 and 0002̄ are similar. The preferential clarity of these two disks is explained using Bloch-wave dynamical theory. To further support the explanation, we compare the results of GaN case. On the basis of our analysis, we conclude that the CBED patterns of the <112̄0 > zone-axis are more useful for accurately determining AlN polarity compared to the CBED patterns along the <11̄00 > zone-axis.