The emerging field of graphene brings together scientists and engineers as the discovered fundamental properties and effects encountered in this new material can be rapidly exploited for practical applications. There is potential for a two-dimensional graphene-based technology and recent works have already demonstrated the utility of graphene in building nanoelectromechanical systems, complex electronic circuits, photodetectors and ultrafast lasers. The state-of-the-art of substrate-suported graphene growth, and the current fundamental understanding of the electromechanical properties of graphene and graphene nanoribbons, represent important knowledge for developing new applications.
Si and Ge nanowires have potential applications in a wide variety of areas including thermoelectrics, optoelectronics,
and sensors. Nanowires are most commonly grown via the vapor-liquid-solid (VLS) process. In this method, a vapor
phase containing the material of interest preferentially dissociates at a liquid catalyst and is incorporated as a solid at
the solid-liquid interface. However, despite 40 years of research in this area, several aspects of nanowire growth
remain unclear, even for relatively simple elemental Si and Ge wires. Here, we will review our <i>in situ</i> transmission
electron microscopy (TEM) investigations of Si and Ge nanowire growth kinetics. The observations are carried out in
an ultra-high vacuum TEM (the IBM UHV-TEM) equipped with facilities for deposition <i>during</i> observation. Using
Au as the catalyst, we study the VLS growth of Si and Ge nanowires as a function of disilane or digermane pressure
and substrate temperature. We find surprisingly different growth mechanisms for the two materials. The insights
gained from <i>in situ</i> results may help devise methods for large-scale fabrication of wires with controlled architecture.