School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
ACS Nano. 2015 Feb 24;9(2):1250-6. doi: 10.1021/nn504974z. Epub 2015 Jan 27.
Spatial control of carrier density is critical for engineering and exploring the interactions of localized surface plasmon resonances (LSPRs) in nanoscale semiconductors. Here, we couple in situ infrared spectral response measurements and discrete dipole approximation (DDA) calculations to show the impact of axially graded carrier density profiles on the optical properties of mid-infrared LSPRs supported by Si nanowires synthesized by the vapor-liquid-solid technique. The region immediately adjacent to each intentionally encoded resonator (i.e., doped segment) can exhibit residual carrier densities as high as 10(20) cm(-3), which strongly modifies both near- and far-field behavior. Lowering substrate temperature during the spacer segment growth reduces this residual carrier density and results in a spectral response that is indistinguishable from nanowires with ideal, atomically abrupt carrier density profiles. Our experiments have important implications for the control of near-field plasmonic phenomena in semiconductor nanowires, and demonstrate methods for determining and controlling axial dopant profile in these systems.
载流子密度的空间控制对于工程设计和探索纳米尺度半导体中局域表面等离子体共振（LSPR）的相互作用至关重要。在这里，我们将原位红外光谱响应测量和离散偶极子近似（DDA）计算相结合，以展示轴向渐变载流子密度分布对通过汽-液-固技术合成的 Si 纳米线中支持的中红外 LSPR 的光学性质的影响。每个有意编码的谐振器（即掺杂段）附近的区域都可以表现出高达 10^20cm^-3 的残余载流子密度，这强烈改变了近场和远场行为。在间隔段生长过程中降低衬底温度可以降低这种残余载流子密度，并导致与具有理想原子状陡变载流子密度分布的纳米线无法区分的光谱响应。我们的实验对控制半导体纳米线中的近场等离子体现象具有重要意义，并展示了在这些系统中确定和控制轴向掺杂轮廓的方法。
