Materials Science and Engineering, Northwestern University, 2220 Campus Dr., Evanston, Illinois 60208, USA.
Nano Lett. 2013 Jan 9;13(1):199-206. doi: 10.1021/nl3038695. Epub 2012 Dec 18.
The vapor-liquid-solid (VLS) process of semiconductor nanowire growth is an attractive approach to low-dimensional materials and heterostructures because it provides a mechanism to modulate, in situ, nanowire composition and doping, but the ultimate limits on doping control are ultimately dictated by the growth process itself. Under widely used conditions for the chemical vapor deposition growth of Si and Ge nanowires from a Au catalyst droplet, we find that dopants incorporated from the liquid are not uniformly distributed. Specifically, atom probe tomographic analysis revealed up to 100-fold enhancements in dopant concentration near the VLS trijunction in both B-doped Si and P-doped Ge nanowires. We hypothesize that radial and azimuthal inhomogeneities arise from a faceted liquid-solid interface present during nanowire growth, and we present a simple model to account for the distribution. As the same segregation behavior was observed in two distinct semiconductors with different dopants, the observed inhomogeneity is likely to be present in other VLS grown nanowires.
半导体纳米线生长的汽-液-固（VLS）过程是一种用于低维材料和异质结构的有吸引力的方法，因为它提供了一种原位调节纳米线组成和掺杂的机制，但掺杂控制的最终极限最终由生长过程本身决定。在使用广泛的 Au 催化剂液滴化学气相沉积生长 Si 和 Ge 纳米线的条件下，我们发现从液体中掺入的掺杂剂分布不均匀。具体来说，原子探针断层分析显示，在 B 掺杂 Si 和 P 掺杂 Ge 纳米线的 VLS 三结附近，掺杂剂浓度高达 100 倍增强。我们假设，由于在纳米线生长过程中存在具有面心立方结构的固-液界面，因此出现了径向和方位不均匀性，并提出了一个简单的模型来解释这种分布。由于在两种具有不同掺杂剂的不同半导体中观察到相同的分凝行为，因此观察到的不均匀性很可能存在于其他 VLS 生长的纳米线中。
