This grant supports development of a low-temperature, ultra-high vacuum, scanning tunneling microscope, which employs two 100% spin-polarized tips. In this new instrument spin-polarized electrons will tunnel into GaAs at one location, traverse through a small region of the sample, and then tunnel out through another tunnel junction. To achieve this, a novel double-cleaved sample preparation procedure will be developed that uses two STM tips separated by an adjustable parameter from a few nanometers to millimeters. This system will be used to study the coherent transport properties of spin-polarized electrons and, in addition, will allow the study of quantum mechanical transport properties for coupled spin-dependent tunneling junctions. A coherent electron spin current will be injected using a ferromagnetic-metal STM tip (100% spin-polarized single-crystal Ni<110> wire), and then coherently removed using another ferromagnetic-metal STM tip. By being at low temperatures the spin-relaxation lifetime is significantly extended, allowing high signal-to-noise ratio data acquisition. This development is complimented with an educational program designed to enhance the understanding of science by the general public.
This equipment is critical for studying the complex properties of spintronics devices. Students will gain valuable skills in the development of this equipment and will be able to transfer the technology to other interested parties upon graduation. The revolutionary idea of spintronics currently hinges on discovering how to coherently transfer the electron spin from one material to another. This research can provide significant guidance toward achieving this goal, thereby influencing the research fields of surface physics, magnetism, device physics, basic electron-spin physics, electronic materials, and microscopy.
