Development of an Ultrafast Scanning Tunneling Microscope for Dynamic Surface Studies

该奖项为超高速扫描隧道显微镜的开发提供了支持，该显微镜能够研究各种表面现象。为了确保隧道的表面和尖端条件的稳定和可重复性，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。该显微镜将采用隧道结混合技术在皮秒时间尺度上实现分辨率。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的快速过程。利用这种技术最大限度地提高时间分辨率，并向飞秒时间尺度推进，将需要使用带有集成光导开关的纳米制造隧道尖端。这些提示的设计和开发研究将作为与阿尔伯塔大学和阿尔伯塔微电子中心合作努力的一部分进行。阿尔伯塔大学的工作还将包括组装一个脉冲宽度为100秒的钛蓝宝石激光系统，该系统将首先用于在环境条件下测试和评估微制造尖端，然后与超高真空隧道显微镜结合使用。该仪器的发展将为扫描隧道显微镜开辟一个新的维度：有机会在原子时间尺度和原子长度尺度上探测系统。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的缺陷动力学，超导体的非平衡响应，以及光激发分子中结构重配置和电荷转移的动力学。进行此类研究的能力将使扫描隧道显微镜成为所有四个（时空）维度的高分辨率探测器。

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.