Development of an Ultrafast Scanning Tunneling Microscope for Dynamic Surface Studies

小行星9625749 该奖项为能够研究各种表面现象的超快扫描隧道显微镜的开发提供了支持。 为了确保隧道的稳定和可再现的表面和尖端条件，显微镜将在超高真空中使用标准的高真空室系统进行操作，该系统具有完整的表面分析和制备工具。 该显微镜将利用隧道结混合技术实现皮秒时间尺度的分辨率。 在这种技术中，样品和显微镜之间的隧道结的固有非线性与光学发射的高速电脉冲相结合，允许检测和测量样品表面上的快速过程。 努力最大限度地利用这种技术的时间分辨率，并推向飞秒时间尺度，将需要使用纳米制造的隧道尖端与集成光电导开关。 将与阿尔伯塔大学和阿尔伯塔微电子中心合作，对这些尖端的设计和开发进行研究。 在阿尔伯塔大学的努力还将包括一个100 fs脉冲宽度钛：蓝宝石激光系统，将首先用于在环境条件下的微加工尖端的测试和评估，后来结合超高真空隧道显微镜组装。 该仪器的开发将为扫描隧道显微镜开辟一个新的维度：在原子时间尺度和原子长度尺度上探测系统的机会。 这种能力将允许研究各种各样的系统，包括半导体和异质结构中缺陷的动力学，超导体的非平衡响应，以及光激发分子中结构重构和电荷转移的动力学。 进行这种研究的能力将使扫描隧道显微镜成为所有四维（时空）的高分辨率探针。

9625749 Nunes This award provides support for the development of an ultrafast scanning tunneling microscope capable of investigating a wide variety of surface phenomena. In order to ensure stable and reproducible surface and tip conditions for tunneling, the microscope will be operated in ultra-high vacuum using a standard high-vacuum chamber system with a full complement of surface analysis and preparation tools. The microscope will achieve resolution on picosecond time scales using the technique of tunnel junction mixing. In this technique, the intrinsic nonlinearity of the tunnel junction between the sample and microscope in combination with an optically-launched high-speed electrical pulse, allows the detection and measurement of fast processes on the sample surface. Efforts to maximize the time resolution available with this technique, and to push towards femtosecond time scales, will require the use of nano- fabricated tunneling tips with integral photoconductive switches. Research on the design and development of these tips will be carried out as part of a collaborative effort with the University of Alberta and the Alberta Microelectronics Centre. The effort at the University of Alberta will also include the assembly of a 100 fs pulse width Ti:sapphire laser system which will first be used in the testing and evaluation of the microfabricated tips under ambient conditions, and later combined with the ultra-high vacuum tunneling microscope. The development of this instrument will open up a new dimension in scanning tunneling microscopy: The opportunity to probe systems on atomic time scales as well as atomic length scales. This capability will allow the study of a wide variety of systems, including the dynamics of defects in semiconductors and heterostructures, the nonequilibrium response of superconductors, and the dynamics of structural reconfigurations and charge transfer in optically excited molecules. The ability to carry out such stu dies will make the scanning tunneling microscope a high-resolution probe in all four (space-time) dimensions.