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首页> 外文学位 >Development of a scanning tunneling potentiometry system for measurement of electronic transport at short length scales.
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Development of a scanning tunneling potentiometry system for measurement of electronic transport at short length scales.

机译：开发了一种扫描隧道电位计系统，用于测量短尺度的电子传输。

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摘要

It is clear that complete understanding of macroscopic properties of materials is impossible without a thorough knowledge of behavior at the smallest length scales. While the past 25 years have witnessed major advances in a variety of techniques that probe the nanoscale properties of matter, electrical transport measurements -- the heart of condensed matter research -- have lagged behind, never progressing beyond bulk measurements. This thesis describes a scanning tunneling potentiometry (STP) system developed to simultaneously map the transport-related electrochemical potential distribution of a biased sample along with its surface topography, extending electronic transport measurements to the nanoscale. Combining a novel sample biasing technique with a continuous current-nulling feedback scheme pushes the noise performance of the measurement to its fundamental limit - the Johnson noise of the STM tunnel junction. The resulting 130 nV voltage sensitivity allows us to spatially resolve local potentials at scales down to 2 nm, while maintaining atomic scale STM imaging, all at scan sizes of up to 15 microns. A mm-range two-dimensional coarse positioning stage and the ability to operate from liquid helium to room temperature with a fast turn-around time greatly expand the versatility of the instrument. Use of carefully selected model materials, combined with excellent topographic and voltage resolution has allowed us to distinguish measurement artifacts caused by surface roughness from true potentiometric features, a major problem in previous STP measurements. The measurements demonstrate that STP can produce physically meaningful results for homogeneous transport as well as non-uniform conduction dominated by material microstructures. Measurements of several physically interesting materials systems are presented as well, revealing new behaviors at the smallest length sales. The results establish scanning tunneling potentiometry as a useful tool for physics and materials science.
机译：很明显，如果没有对最小长度尺度上行为的透彻了解，就不可能完全了解材料的宏观特性。在过去的25年中，探测物质的纳米级特性的各种技术取得了重大进展，但电迁移测量（凝聚物质研究的核心）却落后了，从未超越体积测量。本论文介绍了一种扫描隧道电位仪（STP）系统，该系统可同时绘制偏置样品的与运输相关的电化学势分布及其表面形貌，从而将电子传输测量范围扩展到纳米级。将新颖的采样偏置技术与连续的零电流反馈方案相结合，可将测量的噪声性能推至其基本极限-STM隧道结的Johnson噪声。所产生的130 nV电压灵敏度使我们能够在低至2 nm的范围内空间解析局部电势，同时保持原子级STM成像，所有扫描尺寸均达到15微米。毫米范围的二维粗定位台以及从液氦到室温的操作能力以及快速的周转时间极大地扩展了仪器的多功能性。使用精心挑选的模型材料，再加上出色的形貌和电压分辨率，使我们能够将表面粗糙度引起的测量伪影与真实的电位测量功能区分开，这是以前的STP测量中的一个主要问题。测量结果表明，STP可以产生均质传输以及以材料微结构为主的非均匀传导的物理意义的结果。还介绍了几种对物理有趣的材料系统的测量，以最小的长度销售揭示了新的行为。结果建立了扫描隧道电位法，成为物理和材料科学的有用工具。

著录项

  • 作者

    Rozler, Michael.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 91 p.
  • 总页数 91
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

  • 入库时间 2022-08-17 11:38:25

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