Growth Pathways in Ultralow Temperature Ge Nucleation from Au

Device integration on flexible or low-cost substrates, hag, driven, interest in the low-temperature,growth of semiconduct nanostructures. Using in situ electron microscopy, we examine the Au catalyzed growth of crystalline Ge at temperatures as low as 150 degrees C. For this materials system, the model for low temperature growth of nanowires, we find three distinct reaction pathways The lowest temperature reactions are distinguished by the absence of any purely liquid state. From measurements of reaction rates and parameters such as super saturation, we explain the sequence of pathways as arising from a kinetic competition between the imposed time scale for Ge addition and the inherent time scale for Ge nucleation. This enables an understanding of the conditions tinder which catalytic Ge growth can occur at very low temperatures, with implications for nanostructure formation on temperature sensitive substrates.