Programming Semiconductor Nanowire Composition with Sub-100 nm Resolution via the Geode Process

We demonstrate the vapor-liquid-solid growth of single-crystalline i-Si, i-Si/n-Si, and SiGe_1-/SiGe_1- nanowires via the Geode process. By enabling nanowire growth on the large internal surface area of a microcapsule powder, the Geode process improves the scalability of semiconductor nanowire manufacturing while maintaining nanoscale programmability. Here, we show that heat and mass transport limitations introduced by the microcapsule wall are negligible, enabling the same degree of compositional control for nanowires grown inside microcapsules and on conventional flat substrates. Efficient heat and mass transport also minimize the structural variations of nanowires grown in microcapsules with different diameters and wall thicknesses. Nanowires containing at least 16 segments and segment lengths below 75 nm are demonstrated.