| Description |
Realization of next generation spintronic devices will require the use of design and engineering of new materials. In order to reach the performance requirements for spintronic transistor devices to become a reality, spin injection must be extremely efficient at room temperature. Understanding new materials and combinations of materials will enable the injection efficiency required for next-generation devices. Rare earth oxides are explored to determine the feasibility of doping magnetic elements to make new dilute magnetic dielectric materials for spin tunneling injection applications. Samarium Oxide (Sm2O3) doped with a small amount of cobalt (Co) is shown to exhibit a magnetic phenomenon which cannot be accounted for by conventional models. Though the observed magnetic properties appear quite similar to those observed in superparamagnetic systems, the origin of these properties is entirely different. A model, based on the widely accepted bound polaron theory for insulating ferromagnets, is proposed to explain the magnetic behavior of Co doped Sm2O3 films. We have also explored the growth and properties of high quality Tb2O3 thin films with on a variety of substrates in preparation for magnetic doping. We show enhanced dielectric constant related to improved crystal quality compared with previous reports, which makes this material of interest in high-k applications as well. Furthermore, we report room-temperature, all-electrical injection and detection of spin-polarized carriers in silicon using NiFe/MgO tunnel-barrier-contacts. From the magnetic-field dependence of the spin-accumulation voltage, spin-lifetime and diffusion-length of the carriers were determined to be 276 ps and 328 nm, respectively. Attaining spin diffusion lengths of >320 nm in Si channels is a ground breaking step and opens tremendous opportunities for integrating spin functionality into post-Moore-era electronic devices. We have carried out similar research with ZnO channels. We report all-electrical injection and detection of spin-polarized carriers in ZnO using NiFe/MgO tunnel-barrier-contacts. The three-terminal Hanle effect is used to study spin transport in single crystal thin film ZnO grown on sapphire. The results show that spin injection persists up to and above room temperature, with a measured lifetime τs=174 ps at 340K. These results underscore the importance of ZnO as a material for future active spintronics devices. |
