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首页> 外文学位 >Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy.
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Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy.

机译：使用二次谐波产生和瞬态吸收泵浦探针显微镜研究氧化锌棒中的光腔模式和超快载流子动力学。

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摘要

The polydispersity intrinsic to nanoscale and microscale semiconductor materials poses a major challenge to using individual objects as building blocks for device applications. The ability to manipulate the shape of ZnO structures is enormous, making it an ideal material for studying shape-dependent phenomena. We have built a nonlinear microscope used to directly image optical cavity modes in ZnO rods using second-harmonic generation. Images of second-harmonic generation in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second-harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second-harmonic condition that cannot be achieved in bulk ZnO. A more complicated second-harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. Additionally, the nonlinear microscope was combined with transient absorption pump-probe to follow the electron-hole recombination dynamics at different points within individual needle-shaped ZnO rods to characterize spatial differences in dynamical behavior. The results from pump-probe experiments are correlated with spatially resolved ultrafast emission measurements, and scanning electron microscopy provides structural details. Dramatically different electron-hole recombination dynamics are observed in the narrow tips compared to the interior, with the ends exhibiting a greater propensity for electron-hole plasma formation and faster recombination of carriers across the band gap that stem from a physical confinement of the charge carriers. In the interior of the rod, a greater fraction of the electron-hole recombination is trap-mediated and occurs on a significantly longer time scale.
机译：纳米级和微米级半导体材料固有的多分散性给使用单个物体作为器件应用的基础材料提出了重大挑战。操纵ZnO结构形状的能力非常强大，使其成为研究形状相关现象的理想材料。我们建立了一个非线性显微镜，用于使用二次谐波生成直接对ZnO棒中的光学腔模式成像。从单个结构获得的针状ZnO杆中的二次谐波产生的图像显示出沿杆的纵轴增强的二次谐波强度的区域，这些区域周期性地分布并且相对于杆中点对称放置。空间调制是基本光学场耦合到ZnO结构的驻波谐振器模式的直接结果，导致增强的背向散射二次谐波条件，这在块状ZnO中无法实现。当激发低于带隙时，观察到更复杂的二次谐波图像，这归因于低语的画廊模式。此外，将非线性显微镜与瞬态吸收泵浦探针结合，以跟踪各个针状ZnO棒内不同点的电子-空穴复合动力学，以表征动力学行为的空间差异。泵浦探针实验的结果与空间分辨的超快发射测量相关，扫描电子显微镜提供了结构细节。与内部相比，在狭窄的尖端观察到截然不同的电子-空穴复合动力学，其末端表现出更大的电子-空穴等离子体形成倾向，并且由于电荷载流子的物理限制，整个带隙中的载流子重组更快。在棒的内部，大部分电子-空穴复合是陷阱介导的，并且发生的时间明显更长。

著录项

  • 作者

    Mehl, Brian Peter.;

  • 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 Chemistry Physical.;Engineering Materials Science.;Health Sciences Pharmacy.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 147 p.
  • 总页数 147
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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