  InN quantum dots (QDs) are considered to be promising nanostructures for
different device applications. For any hexagonal AB stacking semiconductor
system, polarity is an important feature which affects the electronic
properties. Therefore, the determination of this characteristic on any wurtzite
(semi)polar III nitride compound or alloy is essential for defining its
applicability. In this paper, the polarity of InN QDs grown on silicon by
indium droplet epitaxy plus nitridation and annealing was determined by a
modified approach combining exit wave reconstruction with negative spherical
aberration high resolution lattice imaging using TEM. Comparing the micrographs
of two QDs from the same TEM specimen with the simulated images of InN slab
structures generated under the same conditions as of the experiments, it was
confirmed that the QDs of the present study are N polar. Given that the
settlement of material's polarity has always been a tedious, indirect and
controversial issue, the major value of our proposal is to provide a
straightforward procedure to determine the polar direction from
atomic-resolution focal series images.
