Magnetic Interactions in Mesoscopic Transport Studied by Millikelvin Scanning Probe Microscopy

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w:\awards\awards96\*.doc 9623847 Nunes Scanning probe microscopy techniques will be applied to the study of magnetic interactions in quantum transport at milliKelvin temperatures. Force microscope tips with deposited magnetic impurities will be used to place defects of a known type at known positions in a mesoscopic sample. The effect of spin scattering from these artificially introduced defects will be studied via conductance fluctuations and Aharonov-Bohm oscillations in narrow wires and rings. These experiments will provide insight into inelastic scattering processes in small devices, and offer sensitive tests of universal conductance fluctuation theory. The ability to probe and manipulate the defects in nanoscale wires and devices will ultimately allow the investigation of disorder in quantum transport at the single defect level. %%% This research program will apply techniques from the rapidly growing field of scanning probe microscopy to the study and manipulation of defects in nanoscale electronic devices. In the past, electrical measurements have only been sensitive to the average properties of a device, rather than to the individual defects out of which the average behavior is built up. The ability of scanned probe microscopes to provide spatially resolved, local information will allow us to look beneath the general properties to the underlying behavior on the atomic scale. This information will provide new physical insights unobtainable by any other means---insights which will be required for predicting and understanding the nano-electronics of the future in which the atomic-scale disorder will inevitably influence the behavior of nominally "identical" devices. ***