Research in this laboratory is focused on the fabrication and characterization of thin-film structures and is based on the recognition that unusual physical phenomena occur in restricted dimensions. Systems under study include metals, composites, semiconductors, dielectrics, superconductors, complex oxides, graphene and carbon-sixty molecular monolayers. Thin-film deposition is accomplished by the vacuum techniques of thermal sublimation by resistive heating, reactive ion beam sputter deposition, electron beam melting and dc/rf sputtering. Graphene is grown by chemical vapor deposition. Characterization techniques available in the laboratory include tunneling, dielectric spectroscopy (10 mHz- 30MHz), atomic force microscopy, electrostatic force microscopy, ellipsometry, and electrical transport at high fields (7T) and over a broad temperature range (1.4-400 K). A unique capability (SHIVA, Sample Handling In VAcuum) has also been developed. This capability allows the monitoring of the optical and electrical properties of thin films as they are being deposited followed by a post-deposition transfer (without exposure to air) of the completed film structure into a low temperature cryostat for magneto-transport measurements.

A sampling of collaborative projects presently being pursued in our group includes:
  • Understanding the effect of microstructure on magnetization, electronic transport and magnetoresistance in the coalescence regime of thin conducting films.

  • In situ studies of weak locallization and interaction effects and their effect on magnetism in disordered ultra-thin transition metal and rare earth films. Post deposition ion milling is utilized to smooth the films and decrease their resistance.

  • Development of dielectrics with high breakdown strengths and a low density of interface trapping states for electric-field tuning of the magnetic, superconducting and optical properties of thin films with low carrier density.

  • A study of magnetocapacitance and spin-dependent electric potentials in trilayer capacitor structures where the spacing between magnetic electrodes is thin enough to assure that the interface capacitance dominates. Materials being studied include transition metal ferromagnets, complex oxides and manganites.

  • Development of a new technique to simultaneously measure magnetoimpedance in both the perpendicular and parallel directions of anisotropic thin films.

  • Characterization of magnetoresistance and magnetocapacitance in diluted magnetic semiconductors and complex oxides exhibiting ferromagnetism near room temperature.

  • A study of enhanced light transmission in hole arrrays due to resonant scattering and trapped modes.
  • Fundamental studies of transport in doped graphite and graphene.
  • Graphene(chemically doped)/semiconductor Schottky barriers are being studied for solar cell applications.