Diameter-Controlled Synthesis of Phase-Change Germanium Telluride Nanowires via the Vapor−Liquid−Solid Mechanism

Abstract

The ability to control the size of nanostructures still presents one of the biggest challenges in nanosciences. While impressive progress has been made toward diameter-controlled synthesis of nanocrystals via solution-phase chemical techniques, control over nanowire diameters grown via the gas-phase vapor−liquid−solid mechanism is still challenging. Diameter-controlled growth of nanowires have been reported by controlling the size of the metal nanocatalysts, which is a general technique. However, the complex dynamics of gas-phase reactants and their reaction with catalysts requires in-depth understanding of the effect of various growth parameters on the size of catalysts during growth, which makes diameter-controlled growth of nanowires challenging. Here, we report diameter-controlled growth of GeTe nanowires, which are important materials for phase-change memory devices. Recently, several groups have investigated phase-change nanowires for memory applications, but the ability to control their diameters has been lacking. This lack of nanowire size control has made investigation of phase-change memory switching difficult for both fundamental science and device applications. We find that by controlling the rate of supercooling and the reactant supply rate we can produce large quantities of nanowires with uniform, narrow diameter distributions. The effects of various growth parameters such as temperature, pressure, and reactant supply rate on nanowire morphologies are discussed.