Calculation of the diameter-dependent polytypism in GaAs nanowires from an atomic motif expansion of the formation energy.

In: Physical Review B, Jg. 84 (2011) ; Nr. 7, S. 075455/1-8
ISSN: 1550-235X, 1098-0121
Zeitschriftenaufsatz / Fach: Physik
Fakultät für Physik » Theoretische Physik
Abstract:
The formation energies of GaAs nanowires have been calculated from a structural motif approach supported by first-principles data for small-diameter nanowires. GaAs bulk material has zincblende (ZB) structure, but the ground state of nanowires may be either ZB or wurtzite (WZ), possibly depending on energetic contributions from their surfaces and edges. The calculated nanowires are cut from the bulk material in the [111] direction and the [0001] direction for ZB and WZ structure, respectively. We consider nanowires with hexagonal cross sections and {11\overline{2} 0} and {10\overline{1} 0} facets in the case of WZ, and {10\overline{1}̅ } and {11\overline{2} } for ZB nanowires. It is found that the WZ formation energy of small nanowires is lower than the ZB one due to the lower WZ surface energy. This holds if edge energies are neglected. The role of additional dangling bonds at the edges and its effect on the WZ-ZB transition is discussed.