Ge in-plane nanowires grown by MBE: influence of surface treatment

• Published in: CrystEngComm 2013-01, Vol.15 (17), p.3478-3483
• Main Authors: Bansen, Roman, Schmidtbauer, Jan, Gurke, Robert, Teubner, Thomas, Heimburger, Robert, Boeck, Torsten
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Germanium; Molecular beam epitaxy; Nanostructure; Nanowires; Passivation; Scanning electron microscopy; Wire
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c3ce27047e

We present a detailed study of morphological phenomena during molecular beam epitaxy (MBE) of Ge nanowires on Ge substrates by means of the vapor-liquid-solid mechanism. Different wet chemical surface passivation methods were tested for their effect on Ge nanowire growth. Clean, smooth and well-passivated surfaces enable the preferential formation of in-plane nanowires, instead of conventional out-of-plane nanowires. Depending on the type of passivation, different growth directions of the self-aligned in-plane wires were observed: exclusively -grown wires on substrates with a very stable passivation layer, both and growth on substrates with a less stable passivation. The morphology of the wires was studied by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). For the -grown in-plane wires, nanofaceting of the top and side walls was observed. Based on the analysis, a coherent hypothesis is formulated to explain the experimental findings. Nanowires aligned laterally along the substrate surface preferentially form on particularly smooth and well-passivated surfaces. Depending on the wet chemical surface passivation method, different growth directions of the self-aligned in-plane wires can be observed.