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Optical spectroscopy of new materials

The development of new wide band gap materials and devices is a focal point of physicists, chemists, and engineers at OSU. My lab is the home for spectroscopic measurements of these new materials. We measure the reflection and transmission of thin films and powdered samples of new materials in order to determine refractive indices, film thicknesses, absorption coefficients and band gaps. My laboratory comprises three spectrometers for measurements on thin film samples and powdered samples over the ultraviolet to infrared wavelength range 200 nm - 2500 nm. The system can also take spectra of samples cooled to 80K. The wide band gap materials work is a collaboration with Prof. Janet Tate (OSU Physics), Prof. Doug Keszler (OSU Chemistry), and Prof. John Wager (OSU Electrical Engineering).


  • "Chalcogen-based transparent conductors." J. Tate, P. F. Newhouse, R. Kykyneshi, P. A. Hersh, J. Kinney, D. H. McIntyre, D. A. Keszler, Thin Solid Films 516, 5795-5799 (2008).
  • "Electrical and optical properties of epitaxial transparent conductive BaCuTeF thin films deposited by pulsed laser deposition," R. Kykyneshi, D. H. McIntyre, J. Tate, C.-H. Park, and D. A. Keszler, Solid State Sci. 10, 921-927 (2008).
  • "Origin of p-type conduction in single-crystal CuAlO2," (J. Tate, H. L. Ju, J. C. Moon, A. Zakutayev, A. P. Richard, J. Russell, and D. H. McIntyre, Phys. Rev. B 80, 165206 (2009).
  • "Tunable properties of wide-bandgap p-type BaCu(Ch1-xCh'x)F (Ch = S , Se , Te) thin-film solid solutions," A. Zakutayev, D. H. McIntyre, G. Schneider, R. Kykyneshi, D. A. Keszler, C.-H. Park, and J. Tate, Thin Solid Films 518, 5494-5500 (2010).
  • "Electronic structure and excitonic absorption in BaCuChF (Ch = S , Se , Te) ," A. Zakutayev, R. Kykyneshi, G. Schneider, D. H. McIntyre, and J. Tate, Phys. Rev. B 81, 155103 (2010).
By measuring the reflection and transmission of a thin film sample, we can determine the film thickness, refractive index, absorption coefficent, and band gap. The ratio T/(1-R) provide a measure of the absorption coefficent that is free of the interference fringes evident in both the reflection and transmission spectra. This example shows this procedure for a film of In2O3:W. This gap is direct, so the square of the absorption coefficient times the energy produces a straight line that determines the band gap energy.
Ba-based chalcogenide-fluorides BaCuChF (Ch = S , Se , Te) and their solid solutions, show p-type conductivity, wide direct optical band gaps, and room temperature excitons. BaCuChF have two series of 3D Wannier-Mott excitons associated with two spin-orbit split valence bands. Spin-orbit splitting increases with increasing atomic weight of the chalcogen in BaCu(Ch1-xCh'x)F.