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MM: Fachverband Metall- und Materialphysik

MM 22: Topical Session TEM VI

MM 22.1: Topical Talk

Mittwoch, 16. März 2011, 11:00–11:30, IFW B

In-situ TEM: Atomistic Insights into Crystallisation — •Christina Scheu — Department of Chemistry & Center for NanoScience (CeNS), Ludwig-Maximilians-University, Munich, Germany

Ultrathin non-conducting nanowires are potential candidates for application in electronic devices and for medical treatments. Recently we studied the self-catalytic vapor-liquid-solid (VLS) growth of alumina nanowires in-situ at 750 degrees Celsius in a high voltage transmission electron microscope [1]. The atomic scale observation revealed that the growth of the nanowire in [0001] direction takes place layer-by-layer involving a two-step mechanism. Oscillatory growth and dissolution reactions alternate at the top rim of the nanowire which is in contact to the liquid Al droplet and the vapor phase leading to periodical changes of the triple junction configuration. The dissolution reaction of the crystalline top rim supplies the oxygen which is required to grow a new (0006) alumina layer [1]. The growth of the (0006) layer is relatively fast since the Al atoms in the liquid adjacent to the crystalline alumina wire possess already similar position as in the solid [2]. This leads to an easy pathway for the interfacial diffusion of oxygen. The rate limiting step for growth of the alumina nanowire is the oxygen transport after completion of a new (0006) alumina layer when the crystalline rim is formed.

[1] Oh, Chisholm, Kauffmann, Kaplan, Luo, Rühle, Scheu, Science 330, 489 (2010). [2] Oh, Kauffmann, Scheu, Kaplan, Rühle, Science 310, 661 (2005).