MRI: Equipment Development: Development of Advanced Scanning Probe Techniques for Spintronics and Nanodevice Research

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Intellectual MeritScanning Probe Microscopy (STM, AFM, BEEM etc) has revolutionized the way we visualize and manipulate individual atoms, chemical bonds, and electron waves. A successful development of a new technique and instrument that can enable us to visualize and manipulate magnetic states and even a single spin would clearly be another great milestone in device and materials research. An STM is just a two terminal device but the investigation of spin-dependent nanoscale transport phenomenon, similar to transistor action, requires a three terminal device arrangement. Here we propose to construct a dual-probe scanning tunneling microscope operating in a low temperature, high magnetic field and ultra high vacuum environment. Such an instrument not only maintains independent scanning capability but also is capable of positioning the two tips (electrodes) at nanoscale distances and desired locations, forming a nano-scale three-terminal device with the specimen. Using spin polarized STM tips, this instrument will enable us to inject, detect and manipulate both charges and spins with the controllability down to the atomic scale. It should enable many new experiments including but not limited to: (a) mapping local spin polarization in a dilute magnetic semiconductor based on the Zeeman splitting of the energy spectra of an electron in a high magnetic field; (b) investigating spin injection from a ferromagnetic metal into a semiconductor using a dual tip BEEM; (c) demonstrations of spin FET devices;These studies should enable deeper fundamental understanding of ferromagnetism in semiconductors and other device materials, provide guidance for improving materials performance such as higher Curie temperature and long mean free path for spin coherent carriers, and enable development of novel device concepts based on spin degrees of freedom, in addition to charge degrees of freedom. The unique and powerful capabilities of the proposed instrument cannot be achieved by any current conventional SPM instrument or lithographical fabrication technique.Broader ImpactIt will attract and enable the undergraduate, graduate students, and postdoctoral fellows to explore the most forefront nanoscale device and materials physics, particularly spintronics. This proposed research involves a broad set of experimental skills and should provide a rather special opportunity for training the next generation of experimental physicists and engineers.