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首页> 外文学位 >Direct Imaging of Ultrafast Charge Carrier Dynamics in Semiconducting Nanowires Using Two-Photon Excitation and Spatially-Separated Pump-Probe Microscopy.
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Direct Imaging of Ultrafast Charge Carrier Dynamics in Semiconducting Nanowires Using Two-Photon Excitation and Spatially-Separated Pump-Probe Microscopy.

机译：使用双光子激发和空间分离的泵浦探针显微镜对半导体纳米线中的超快电荷载流子动力学进行直接成像。

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摘要

The increasing use of nanoscale materials in scientific research and device design places a greater emphasis on characterizing the heterogeneity of nanostructures. When designing electronic components around the use of individual nanoparticles, it is important to understand variability between seemingly identical particles produced in the same synthesis. To do this, we have developed an ultrafast optical microscope capable of studying single nanostructures with spatial resolution of hundreds of nanometers. Emission images of zinc oxide needle-like nanowires show a modulated pattern along the long axis of the wire that are attributed to the coupling of the optical field into structurally dependent resonance modes. Simulations suggest that these are size dependent hybrid modes, containing character of both whispering gallery and Fabry-Perot modes. By incorporating transient absorption pump-probe techniques into the microscope design, we can observe the recombination dynamics of excited carriers on femtosecond timescales following excitation. Due to the high resolution of the instrument, it is possible to observe the dynamics at different locations within a single nanostructure. This technique is used to study the correlation between the decay kinetics of silicon nanowires and doping density for a variety of surface treatments. The motion of excited carriers in silicon nanowires was directly imaged by holding the pump beam in a particular location and scanning the probe beam over the entire structure. The resulting images show free carriers spreading out from the area of excitation, leaving the immobile trapped carriers behind.
机译：纳米材料在科学研究和设备设计中的使用越来越多，这更加着重于表征纳米结构的异质性。在围绕单个纳米粒子的用途设计电子组件时，重要的是要了解在同一合成过程中产生的看似相同的粒子之间的变异性。为此，我们开发了一种超快速光学显微镜，能够研究具有数百纳米空间分辨率的单个纳米结构。氧化锌针状纳米线的发射图像沿线的长轴显示调制模式，这归因于将光场耦合到与结构相关的共振模式。仿真表明，这些是大小相关的混合模式，包含耳语画廊和Fabry-Perot模式的特征。通过将瞬态吸收泵浦探针技术整合到显微镜设计中，我们可以在激发后的飞秒时间尺度上观察激发载流子的重组动力学。由于仪器的高分辨率，因此可以观察单个纳米结构内不同位置的动力学。该技术用于研究各种表面处理的硅纳米线的衰减动力学与掺杂密度之间的相关性。通过将泵浦光束保持在特定位置并在整个结构上扫描探测光束，可以直接对硅纳米线中激发的载流子的运动进行成像。生成的图像显示自由载流子从激发区域扩展开来，将固定不动的捕获载流子留在后面。

著录项

  • 作者

    Kirschbrown, Justin Robert.;

  • 作者单位

    The University of North Carolina at Chapel Hill.;

  • 授予单位 The University of North Carolina at Chapel Hill.;
  • 学科 Engineering Materials Science.;Physics Optics.;Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 124 p.
  • 总页数 124
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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