1. Intellectual Merit We have recently demonstrated experimentally that hybrid thin film structures possessing an appropriately selected geometric interface between a semiconductor and a metal display a new phenomenon that has been labeled extraordinary magnetoresistance (EMR) and that InSb devices with either internal or external Au shunts exhibit room-temperature EMR as high as 100% to 750,000% at magnetic fields, ranging from 0.05T to 4 Tesla, respectively. These nonmagnetic structures are readily fabricated for practical sensor applications such as read-heads for ultra-high density magnetic recording and rival the performance of conventional sensors based on the giant magnetoresistance (GMR) effect. We have also demonstrated that EMR devices are scalable from macroscopic to nanoscopic dimensions in the range of millimeters to 20 nanometers. It has recently been realized that EMR is but one example of a broad class of geometry-driven interfacial effects in hybrid semiconductor-metal structures. Now a second example of such interfacial phenomena, extraordinary piezoconductivity (EPC), has also been demonstrated by Solin et. al. Here we propose to establish proof of principle, elucidate the underlying physics and develop prototypes of a new class of ifEXXly sensors in which the sensitivity of the metal-semiconductor interface to external perturbations gives rise to similar extraordinary responses. In the case of EMR we propose new prototype array structures for ultra-high resolution magnetic sensing and magnetic imaging. For EPC we propose to clarify the physical principles and to develop prototypes of ultra sensitive and robust strain and pressure sensors. For extraordinary electroconductance (EEC), extraordinary thermoconductance (ETC) and extraordinary optoconductance (EOC) devices we will first establish proof of principal and thereafter move to the prototype stage. All EXX effects are critically dependent on the geometry and physical properties the metal-semiconductor interface. We have already shown that the finite element method (FEM) for modeling EMR provides excellent ixno adjustable parameterl" agreement with experiments while revealing the current and potential distribution in the device in exquisite detail. Therefore, we propose collateral investigation of these novel EXX effects using FEM modeling since it incorporates geometrical issues, while accounting for the attendant complex boundary conditions. FEM is also ideally suited for the design optimization of the structures in order to enhance sensitivity. 2. Broader Impact It is anticipated that the proposed research will have broad beneficial impact on education, technology, and society. It will expose graduate and undergraduate students from a number of disciplines/departments to new experimental techniques, basic physical principles, and novel fabrication methods related to EXX sensor development thus providing interdisciplinary skills that will be mandatory for the next generation of the nation's scientists and engineers. Research results will also be integrated into the undergraduate course work at both institutions and into a special topics course for ioMagnetlo high school students. The proposed research will enhance the opportunity for adding women and under-represented minorities to the Washington University faculty through hiring programs currently chaired by the PI. It will also significantly augment the development of a new campus-wide Materials Initiative/Center that is lead by the PI. EXX sensors could impact a variety of diverse technologies including sensors for medical applications, manufacturing quality control, automobile safety, pollution-control and fuel-efficiency, thermal imaging devices and consumer electronics with obvious social, medical and economic benefits.
