Surface trap density in silicon nanowires (NWs) plays a key role in the performance of many semiconductor NW-based devices. We use pump–probe microscopy to characterize the surface recombination dynamics on a point-by-point basis in 301 silicon NWs grown using the vapor–liquid–solid (VLS) method. The surface recombination velocity (S), a metric of the surface quality that is directly proportional to trap density, is determined by the relationship S = d/4τ from measurements of the recombination lifetime (τ) and NW diameter (d) at distinct spatial locations in individual NWs. We find that S varies by as much as 2 orders of magnitude between NWs grown at the same time but varies only by a factor of 2 or three within an individual NW. Although we find that, as expected, smaller-diameter NWs exhibit shorter τ, we also find that smaller wires exhibit higher values of S; this indicates that τ is shorter both because of the geometrical effect of smaller d and because of a poorer quality surface. These results highlight the need to consider interwire heterogeneity as well as diameter-dependent surface effects when fabricating NW-based devices.

中文翻译：

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用泵浦探针显微镜探测硅纳米线表面陷阱密度的线内，线间和直径相关变化

硅纳米线（NWs）中的表面陷阱密度在许多基于NW的半导体器件的性能中起着关键作用。我们使用泵浦探针显微镜逐点表征了使用气液固（VLS）方法生长的301块硅纳米线中的表面重组动力学。表面重组速度（S）是与陷阱密度成正比的表面质量度量，由关系= S d d /4τ决定，其关系是在不同空间对重组寿命（τ）和NW直径（d）的测量各个NW中的位置。我们发现S同时生长的NW之间的变化幅度最大为2个数量级，但单个NW中的变化幅度仅为2或3倍。尽管我们发现，如预期的那样，较小直径的NW表现出更短的τ，但我们也发现，较小的线材表现出更高的S值；这表明由于较短的d的几何效应和较差的表面质量，τ较短。这些结果凸显了在制造基于NW的器件时需要考虑线间异质性以及与直径相关的表面效应的需求。