Shape Modification of Germanium Nanowires during Ion Irradiation and Subsequent Solid‐Phase Epitaxial Growth

• Published in: Advanced materials interfaces Vol. 5; no. 13
• Main Authors: Camara, Osmane, Hanif, Imran, Tunes, Matheus, Harrison, Robert, Greaves, Graeme, Donnelly, Stephen, Hinks, Jonathan
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 09.07.2018
• Subjects: Annealing; Deformation mechanisms; Epitaxial growth; germanium nanowires; in situ transmission electron microscopy; Ion beams; Ion irradiation; ion‐induced bending; nanomanipulation; Nanowires; Radiation damage; Xenon
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.201800276

During ion irradiation which is often used for the purposes of bandgap engineering, nanostructures can experience a phenomenon known as ion‐induced bending (IIB). The mechanisms behind this permanent deformation are the subject of debate. In this work, germanium nanowires are irradiated with 30 or 70 keV xenon ions to induce bending either away from or toward the ion beam. By comparing experimental results with Monte Carlo calculations, the direction of the bending is found to depend on the damage profile over the cross section of the nanowire. After irradiation, the nanowires are annealed at temperatures up to 440 °C triggering solid‐phase epitaxial growth (SPEG) causing further modification to the deformed nanowires. After IIB, it is observed that nanowires which had bent away from the ion beam then straighten during SPEG while those which had bent toward the ion beam bend even more. This is attributed to differences in the mechanisms responsible for the ion‐beam‐induced bending in opposite directions. Thus, the results reported here give insights into the mechanisms causing the IIB of nanowires and demonstrate how to predict the evolution of nanowires under irradiation and annealing. Finally, they show that, under certain conditions, the bending can even be removed via SPEG. Shape modification of germanium nanowires is induced by xenon ion irradiation at room temperature in situ a transmission electron microscope. Subsequent annealing after irradiation induces further shape modifications of the bent nanowires. To investigate these phenomena, Monte‐Carlo simulations are performed and a method to forecast the behaviour of the nanowires is proposed.