Technical Description: A fundamental approach in materials science involves the fabrication of new materials that couple properties in heterogeneous structures. Transistors for logic devices use the transport of charge in a semiconductor to process information. There are now alternate proposals to use the electron spin to process information, both to reduce power consumption of and add functionality (such as memory) to the transistor. Currently silicon and germanium are widely used as a channel material because they transport charge well, and these semiconductors also transport spin very efficiently. This project focuses on coupling spin from a ferromagnetic oxide to germanium through an insulating oxide barrier. This novel materials system is being developed using atomic layer synthesis by molecular beam epitaxy to manipulate and control spin tunneling into germanium through chemical and structural modifications of the interfaces. Using atomic layer control, key aspects of the interfaces can be manipulated to control spin coupling. These include chemical composition, electric polarization, strain, atomic layer termination, and band offset. Both the physical and electronic structures of each layer are characterized using a combination of in- situ x-ray photoemission spectroscopy, synchrotron x-ray diffraction, x-ray absorption spectroscopy, and transmission electron microscopy. The fully epitaxial design enables the understanding of structural properties governing the function of a promising spin-based device platform.
Non-technical Description: New materials are required to develop new electronic devices for computing applications. These new materials are designed to either require less power or offer additional function in microprocessors. The strategy of the project is to use the spin of an electron as a bit of information rather than charge, as is currently done. The project synthesizes new materials that manipulate electron spin by stacking thin films together one atomic layer at a time. The positions of the atoms are determined using x-ray facilities at the National Laboratories. As part of this work, students and young technicians will be trained in state of the art semiconductor technology, preparing them for careers in the semiconductor industries.