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Advancing microscope and probe design for near-field scanning microwave microscopy.

机译：用于近场扫描微波显微镜的先进显微镜和探头设计。

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摘要

In this thesis, we address the design and application of a microscope and probes for near-field scanning microwave microscopy. We provide an introduction to the development of microwave microscopy and its contributions to material metrology. In particular, we focus on its application to the study of photovoltaics. We then expand beyond these studies to the fabrication of nanowire-based probes for microwave microscopy. These probes provide avenues for advancing an array of scanning probe techniques, including continued measurements on photovoltaics with improved resolution.;To begin, we present a near-field scanning microwave microscope that has been configured for imaging photovoltaic samples. Our system incorporates a Pt-Ir tip inserted into an open-ended coaxial cable allowing the microwave reflection S11 signal to be measured across a sample. A phase-tuning circuit increased impedance-measurement sensitivity by allowing for tuning of the S11 minimum down to -78 dBm. A bias-T and preamplifier enabled simultaneous, non-contact measurement of the DC tip-sample current and a tuning fork feedback system provided simultaneous topographic data. Light-free tuning fork feedback provided characterization of photovoltaic samples both in the dark and under illumination. In addition to single-point measurements on Si and GaAs samples, microwave measurements were obtained on a Cu(In,Ga)Se2 (CIGS) sample. The S11 and DC features were found to spatially broaden around grain boundaries with the sample under illumination. The broadening is attributed to optically-generated charge that becomes trapped and changes the local depletion of the grain boundaries.;Next, we report on the fabrication of a GaN nanowire probe for near-field scanning microwave microscopy. A single nanowire was Pt-bonded to a commercial Si cantilever prior to either an evaporated Ti/Al or an ALD W coating, providing a microwave signal pathway. Testing over a calibration sample shows the probe to have capacitance resolution down to ~0.03 fF with improved sensitivity and reduced uncertainty compared with a commercial microwave probe. Imaging of MoS2 sheets found the probe to be immune to surface contamination, owing to its flexible, high-aspect ratio morphology. By improving microwave and topographical sensitivity in a mechanically robust architecture, this probe serves as an ideal platform for additional complimentary scanning probe techniques.
机译：在本文中，我们讨论了用于近场扫描微波显微镜的显微镜和探头的设计和应用。我们将介绍微波显微镜的发展及其对材料计量学的贡献。特别是，我们专注于将其应用于光伏研究。然后，我们将这些研究扩展到制造用于微波显微镜的基于纳米线的探针。这些探针为推进一系列扫描探针技术提供了途径，包括以提高的分辨率对光伏电池进行连续测量。首先，我们介绍一种已配置用于对光伏样品成像的近场扫描微波显微镜。我们的系统将Pt-Ir尖端插入开放式同轴电缆中，从而可以测量整个样品的微波反射S11信号。相位调谐电路允许将S11最小值调节至-78 dBm，从而提高了阻抗测量的灵敏度。借助偏置T和前置放大器，可以同时进行非接触式直流尖端采样电流测量，而音叉反馈系统则可以提供同步的地形数据。无光的音叉反馈可在黑暗和光照条件下表征光伏样品。除了对Si和GaAs样品进行单点测量外，还对Cu（In，Ga）Se2（CIGS）样品进行了微波测量。发现在光照下，样品的S11和DC特征在晶界周围空间扩展。增宽归因于光生电荷被捕获并改变了晶界的局部损耗。;接下来，我们报道了用于近场扫描微波显微镜的GaN纳米线探针的制造。在蒸镀Ti / Al或ALD W涂层之前，将一条纳米线Pt键合到商用的Si悬臂上，以提供微波信号路径。在校准样品上进行的测试表明，与商用微波探头相比，该探头的电容分辨率低至〜0.03 fF，具有更高的灵敏度和更低的不确定性。 MoS2片的成像发现，该探针由于具有灵活的高长宽比形态而不受表面污染。通过在机械坚固的体系结构中提高微波和地形的敏感性，该探头可作为其他互补扫描探头技术的理想平台。

著录项

  • 作者

    Weber, Joel C.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Mechanical engineering.;Nanotechnology.;Materials science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 159 p.
  • 总页数 159
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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