Abstract

By carrying out chemical vapour deposition of semiconductors in the presence of small particles of a catalytic material, it is possible to grow wirelike structures microns long and below 100nm in diameter. Such nanowires have interesting electronic properties and have already been incorporated into functional devices. Even more applications can be envisaged for branched nanowires or nanowires grown epitaxially at precise locations over an entire wafer. In this presentation we will discuss the growth of epitaxial nanowires in Si and Ge using Au as the catalyst, focusing on the kinetic processes that influence nucleation and final shape. Growth takes place in an environmental TEM , which has capabilities both for evaporating Au onto a clean Si substrate, and for introducing the precursor gases while the sample remains under observation. In situ video rate observations allow us to measure nucleation events and nanowire growth rates, examine the catalyst structure directly, and determine the effects of changes in growth environment on wire shapes. We will focus in particular on the factors that affect shape and the reliability of nucleation, and consider how the in situ results may help in tailoring wire structures for particular applications.