Shape and Orientation Controlled Vapor-Liquid-Solid growth of Si and Ge Nanowires for Monolithic Device Integration

Controlling morphology, electronic properties and growth direction of nanowires is an important aspect regarding their integration into devices on technologically relevant scales.

The purpose of the presentation is to illuminate several aspects regarding the vapour-liquid-solid synthesis of group IV nanowires (Si, Ge), their electrical properties, and the fabrication of devices made thereof. Following an introductory survey of nanowire growth methods, experimental results concerning the epitaxial growth of group IV nanowires are presented. The diameter dependence of the growth velocity and crystallographic growth direction of nanowires, a parameter that is of great importance especially in view of the technical applicability of epitaxially grown nanowires will be discussed. After these partially theoretical considerations with regard to the nanowire morphology, the electrical and optical properties of nanowires will be shown.

Finally we will demonstrate shape transfer from a catalytic particle to the nanowire which has to be seen as a proof-of-concept. Given the immense variety of potential binary alloy seeds, we suppose that this approach should not be limited solely to the materials discussed here – other precursors or catalysts should extend this method to other materials.

Having electronic applications of nanowires in mind, theintegration of nanowires in field-effect transistors is naturally the first step. The feasibility of the fabrication process and the basic functionality of nanowire based devices such as gate all around FETs or “straintronic” devices will be demonstrated.