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Physics Colloquium, May 24, 2005Frontiers in Low-temperature Scanning Tunneling MicroscopyAndreas HeinrichIBM Almaden Research Center, San JoseThe scanning tunneling microscope (STM) is a versatile tool to study nanoscale structures with atomic resolution. In addition to atomic-resolution imaging capabilities, the STM can also move single atoms or molecules. With this ability, we build engineered structures on a surface, one atom or molecule at a time. For example, molecule cascades can be constructed from carbon monoxide molecules, each positioned with atomic precision on a Cu (111) surface at low temperature [1]. In a molecule cascade, the motion of one molecule triggers the motion of the next and so on, analogous to the toppling of a standing row of dominoes. These cascades can be designed to perform all the operations needed for the one-time computation of an arbitrary logic function. The STM can also be used as an atomic-scale spectroscopic tool. Electrons tunneling between the STM tip and sample can transfer energy to atoms or molecules in an inelastic scattering process. Inelastic electron tunneling spectroscopy (IETS) can probe vibrational and magnetic excitations with single-atom sensitivity. I will discuss how IETS was used to build isotope-selected molecule cascades in order to study the propagation rate as a function of molecular mass. The magnetic properties of single atoms can be studied with a novel STM operating at a base temperature of 0.6K in magnetic fields up to 7T. The spectral resolution of IETS under these conditions allows the direct measurement of the Zeeman energy of a single Mn atom supported on a thin film of aluminum oxide grown on a nickel-aluminum surface [2]. In combination with the high spatial resolution of the STM, we are now able to study how the magnetic properties of individual atoms on surfaces change with the local environment. 1. "Molecule cascades", A.J. Heinrich, C.P. Lutz, J.A. Gupta and D.M. Eigler, Science 298, 1381 (2002). 2. "Single atom spin-flip spectroscopy", A.J. Heinrich, J.A. Gupta, C.P. Lutz and D.M. Eigler, Science 306, 466 (2004). 3.30 p.m.,Robert Smith Seminar Room 1080, PRBRefreshments served at 3:00 p.m., Atrium, PRB |
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