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Solid-state tunneling spectroscopy of individual quantum dots.

机译：各个量子点的固态隧道光谱。

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摘要

Quantum dots are gaining importance for their potential applications in the fields of energy harvesting, bio-labeling and treatment, in opto-electronic devices and in photonic devices. For all these applications, it is imperative to know their electronic structure. Although currently several spectroscopic techniques exist to study the electronic structure of these quantum dots, they are accompanied by other effects and do not give purely the electronic structure of the individual quantum dot.;The main goals of this research are to: (1) To study the energy level structure of 'single' quantum dots. (2) Develop a new spectroscopic technique that allows the measurement of the energy level structure of the single quantum dots. (3) Demonstrate that the tunneling spectroscopy can be carried out without other effects such as electron-phonon coupling, non-resonant tunneling, dielectric response of the capping organic layer etc. A major accomplishment from this research is the ability to study directly the energy level structure of individual quantum dots without peak broadening caused by other effects. Spectroscopic measurements were carried out using the double barrier tunnel junction (DBTJ) approach. The DBTJ is formed when a quantum dot placed on the periphery of the vertically separated source-dielectric-drain electrode structure. The measurement units were fabricated using CMOS compatible parallel batch processing techniques.;Spectroscopic measurements were carried out using current-voltage and differential conductance measurements using the lock-in measurement technique. Using these measurements, the energy structure of individual quantum dots were mapped at room temperature as well as low temperatures. Conductance spectra showed that the peak-widths were linearly dependent only on the temperature and are not subject to any other broadening effects. The FWHM of the conductance peaks at 77, 150, 225 and 295K were measured to be 3, 7, 9 and 18meV respectively. The peak widths from this study are narrower when compared to ∼60meV from STM spectroscopy conducted on 6.1nm CdSe quantum dots even at ∼5K. Due to the dependence of the peak width only on the temperature, fine energy level separation measurements are possible using this spectroscopic technique. This narrow peak width allows the measurement of the electronic structure even at room temperature.
机译：量子点在能量收集，生物标记和治疗，光电设备和光子设备等领域的潜在应用正变得越来越重要。对于所有这些应用，必须了解它们的电子结构。尽管目前存在几种用于研究这些量子点的电子结构的光谱技术，但它们伴随着其他作用，并不能完全给出单个量子点的电子结构。这项研究的主要目标是：（1）研究“单个”量子点的能级结构。 （2）开发一种新的光谱技术，该技术可以测量单个量子点的能级结构。 （3）证明可以在没有其他影响的情况下进行隧穿光谱，例如电子-声子耦合，非共振隧穿，覆盖有机层的介电响应等。这项研究的主要成就是能够直接研究能量单个量子点的能级结构，没有其他效应引起的峰展宽。使用双势垒隧道结（DBTJ）方法进行光谱测量。当量子点放置在垂直分离的源极-电介质-漏极电极结构的外围时，形成DBTJ。使用CMOS兼容的并行批处理技术制造测量单元;使用锁定测量技术使用电流-电压和差分电导测量进行光谱测量。使用这些测量，可以在室温和低温下绘制单个量子点的能量结构。电导谱表明，峰宽仅线性依赖于温度，而不受其他任何扩宽影响。在77、150、225和295K处测得的电导峰的FWHM分别为3、7、9和18meV。与在6.1nm CdSe量子点上进行的STM光谱分析得出的约60meV甚至在约5K时相比，该研究的峰宽更窄。由于峰宽仅取决于温度，因此使用此光谱技术可以进行精细的能级分离测量。这种狭窄的峰宽即使在室温下也可以测量电子结构。

著录项

  • 作者

    Subramanian, Ramkumar.;

  • 作者单位

    The University of Texas at Arlington.;

  • 授予单位 The University of Texas at Arlington.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 171 p.
  • 总页数 171
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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