Multiple modulation SPM is a general term for a strategy that extracts information about a surface or nanostructure by combining various signals on samples and tips, using multiple frequencies to distinguish them and accessing multiple harmonics in detection. In addition to the usual conductance, capacitance, surface potential, this approach yields electronic structure, trap state lifetimes, and local dielectric function. Scanning Impedance Microscopy, the first SPM technique to exploit frequency dependence, and its variants will be described. In applications to nanostructure devices, intrinsically higher spatial resolution with respect to scanning gate microscopy is demonstrated, valence band energies of individual defects are quantified, and density of states derived from quantum capacitance extracted. At atomic interfaces in an oxide, local transport anomalies are associated with structurally trapped electrons and associated electric fields are found to cause an unexpected localized phase transition.
Dawn Bonnell is a Trustee Professor of Materials Science at the University of Pennsylvania and the Director of the Nano/Bio Interface Center. She received her PhD from the University of Michigan and was a Fulbright scholar to the Max-Planck-Institute in Stuttgart, Germany, after which she worked at IBM Thomas Watson Research Center. Her current research involves atomistic processes at oxide surfaces, nanometer scale electronic phenomena in materials, and assembly of complex nanostructures. She has authored or coauthored over 180 papers, edited several books, including Scanning Probe Microscopy and Spectroscopy: theory, techniques, and applications.
Her work has been recognized by the Presidential Young Investigators Award, the Ross Coffin Purdy Award, the Staudinger/Durrer Medal, and several distinguished lectureships. Professor Bonnell serves on several editorial boards, national and international advisory committees, is a past president of AVS, served the governing board of the American Institute of Physics, and is a past vice president of the American Ceramic Society. She is a fellow of the Am. Cer. Soc, the American Association for the Advancement of Science, and the AVS.
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