Strain Effects in Epitaxial VO Thin Films on Columnar Buffer-Layer TiO/AlO Virtual Substrates.

Epitaxial VO/TiO thin film heterostructures were grown on (100) (m-cut) AlO substrates via pulsed laser deposition. We have demonstrated the ability to reduce the semiconductor-metal transition (SMT) temperature of VO to ∼44 °C while retaining a 4 order of magnitude SMT using the TiO buffer layer. A combination of electrical transport and X-ray diffraction reciprocal space mapping studies help examine the specific strain states of VO/TiO/AlO heterostructures as a function of TiO film growth temperatures.

Room-Temperature Spin Filtering in Metallic Ferromagnet-Multilayer Graphene-Ferromagnet Junctions.

We report room-temperature negative magnetoresistance in ferromagnet-graphene-ferromagnet (FM|Gr|FM) junctions with minority spin polarization exceeding 80%, consistent with predictions of strong minority spin filtering. We fabricated arrays of such junctions via chemical vapor deposition of multilayer graphene on lattice-matched single-crystal NiFe(111) films and standard photolithographic patterning and etching techniques. The junctions exhibit metallic transport behavior, low resistance, and the negative magnetoresistance characteristic of a minority spin filter interface throughout the temperature range 10 to 300 K.

High-resolution waveguide terahertz spectroscopy of partially oriented organic polycrystalline films.

We have characterized the terahertz (THz) vibrational spectroscopy of organic polycrystalline thin films using the new experimental technique of waveguide terahertz time domain spectroscopy (waveguide THz-TDS). The organic materials used in this study are tetracyanoquinodimethane (TCNQ) and 1,3-dicyanobenzene (13DCB). For each material, a thin film is cast onto one of the inner surfaces of a metal parallel plate waveguide (PPWG), followed by measurement of the low-frequency vibrational spectrum using waveguide THz-TDS.