Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 27: Nanostructures: Low Dimensions

O 27.8: Talk

Tuesday, March 17, 2015, 15:45–16:00, MA 005

Computing Equilibrium Shapes of Wurtzite Crystals: The Example of GaN — •Hong Li^1,2, Lutz Geelhaar², Henning Riechert², and Claudia Draxl¹ — ¹Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, 12489 Berlin, Germany — ²Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany

Crystal morphologies are important for the design and functionality of devices based on low-dimensional nanomaterials. The equilibrium crystal shape (ECS) is a key quantity in this context. It is determined by surface energies, which are hard to access experimentally but can generally be well predicted by first-principles methods. Unfortunately, this is not necessarily so for polar and semipolar surfaces of wurtzite crystals. By extending the concept of Wulff construction, we demonstrate that the ECSs can nevertheless be obtained for this class of materials. For the example of GaN, we identify different crystal shapes depending on the chemical potential. It is shown that the crystal exhibits a rod-like shape along the polar c axis, with top and bottom geometries depending on the chemical potential, while the side walls are formed by both types of nonpolar surfaces. Our results can well explain the experimentally observed nanowire shapes. Beyond that, it opens a perspective to gain insight into morphologies of the entire class of wurtzite materials.