Electron Microscopy of the Operation of Nanoscale Devices
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Electron Microscopy of the Operation of Nanoscale Devices John Cumings1, David Goldhaber-Gordon1, A. Zettl2,3, M.R. McCartney4, and J. C. H. Spence5 1
Department of Physics, Stanford University, Stanford, California; 2Department of Physics, University of California, Berkeley, California; 3Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, California; 4Center for Solid State Science, Arizona State University, Tempe, Arizona; 5Department of Physics and Astronomy, Arizona State University, Tempe, Arizona. ABSTRACT A transmission electron microscope (TEM) is much more than just a tool for imaging the static state of materials. To demonstrate this, we present work on studying the mechanical and electrical properties of carbon nanotube devices. Multiwall carbon nanotubes are concentrically stacked tubular sheets of graphite, where the spacing between each cylinder is simply the natural spacing of graphite. Using a custom-built in-situ nanomanipulation probe, we have shown that it is possible to slide the nanotube layers in a telescopic extension mode that exhibits low friction, demonstrating the potential of nanotubes as the ultimate synthetic nanobearing. During this telescopic extension, the electrical resistance of the nanotube devices increases, opening the possibility that these devices can also be used as nanoscale rheostats. We also briefly describe work on using electron holography inside a TEM to study the electric field distribution in nanotube field-emission devices and on using a nanotube itself as a biprism for electron holography. These measurements together demonstrate the wealth of information that can be obtained and frontiers that can be opened by putting operational nanodevices inside an electron microscope. INTRODUCTION Nanomanipulation is a powerful tool. Atomic manipulation experiments using an STM (scanning tunneling microscope) have already demonstrated that nanomanipulation can facilitate the creation of atomic-scale structures that would be difficult to form or study by any other means [1-5]. The main problem with STM is that it requires a flat, conducting surface to work on. Furthermore, the process of acquiring an image of the surface requires scanning the STM tip back and forth many times, and can it can take several minutes just to acquire a single image. Atomic force microscopy (AFM) [6] and high-speed STM [7] lift some of these limitations, but the full benefits of nanomanipulation have yet to be realized. An alternative approach is to combine the manipulation capabilities of an STM, AFM, or related scanned probe with the imaging capabilities of high-resolution TEM. This allows continuous, real-time imaging during nanomanipulation on both conducting and insulating materials. A nanomanipulation probe, in its simplest form, could simply be thought of as an STM tip. Instead of the location of the tip being controlled by a computer which maps out the surface, control of the position and voltage of the tip is given directly to the operator. It is possible, in princip
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