MSE Seminar Series: John Cumings
Friday, September 16, 2011
Room 2110 Chemical and Nuclear Engineering Bldg.
301 405 5240
In-situ TEM Studies of the Electrical and Magnetic Properties of Novel Nanosystems
Department of Materials Science and Engineering
A. James Clark School of Engineering
University of Maryland
Transmission electron microscopy (TEM) is a powerful tool for determining the structure of materials at the nanoscale, but it also provides high bandwidth for rapid characterization, which is unique among nanoscale imaging techniques. This presents the possibility of studying dynamic prototypical devices and other test structures during their operation, in-situ inside the microscope. In this talk, I will present my work since 2005 here at the University of Maryland building a research effort in the area of in-situ TEM, with a focus on electrical and magnetic nanosystems. The presentation will have two foci, thermal imaging of carbon nanotubes and interacting magnetic nanostructures. For the thermal imaging of carbon nanotubes, we have developed a new thermal imaging technique that we call electron thermal microscopy. Using this technique, we have shown that we can measure and control the thermal contact resistance between carbon nanotubes and neighboring materials, and these results contribute to the general knowledge of these phenomena. Additionally, more recent results on current-carrying nanotubes suggest the existence of a new mechanism of Joule heating at the nanoscale, where a nanotube may dissipate heat directly into a neighboring material without heating itself. On the topic of magnetic nanosystems, I will present work on nanoscale magnetic elements that are arranged in controlled lattices. These structures have been called artificial spin ice, and have been shown to mimic the behavior atomic magnetic moments arranged on analogous lattices of rare-earth magnetic oxides, called spin ice. These lattices exhibit a phenomenon known as frustration, which will be introduced in this context. Other relevant nanosystems will be briefly introduced.