High pressure physics of semiconductor systems; Raman and optical spectroscopy
Phone: (716) 645-2904
Professor Weinstein's research interests are in experimental studies of the optical and high-pressure physics of solids. Raman scattering, luminescence, and other visible/infrared spectroscopies are focused on the phonon and electron excitations in semiconductor crystals, alloys, nanostructures, and glasses. Diamond-anvil cells are employed to probe the hydrostatic- pressure dependence of these excitations and the structural phase transitions in the materials. The most recent studies by Weinstein’s group have explored: correlation between pressure-softening of TA phonons and phase changes, pressure effects in the novel perovskite BaZrS3, and precipitate formation and plasticity under applied pressure in II-VI crystals. (See Selected Publications below.)
Earlier work by Weinstein on phonons, anharmonic interactions, and phase changes in Group IV, III-V, and II-VI crystals led to an understanding of the effects of pressure on the dispersion of optic- and acoustic- branches in these materials across the Brillouin Zone. Subsequent research on the high-pressure phase changes in epitaxial multilayers revealed superpressing behavior that bears on the growth (at 1 atm.) of metastable strained-layer systems. Studies of intrinsic and defect electron states explored how applied pressure tunes the extended-localized nature of impurities in n-type ZnSe and of N-pairs in GaAs1-xNx, and how pressure enhances the lattice relaxation of Zn-vacancies in ZnS. Another area of Weinstein’s interest has been the properties of chalcogenide glasses at both ambient and elevated pressures. Experiments on amorphous Se films show that photo-crystallization is promoted by as-grown interface strain, and studies on several As- and Ge- chalcogenide glasses and crystals find connections between the network dimensionality of bonding and photoelastic behavior.
Professor Weinstein has made significant contributions to high-pressure experimentation by pioneering the use of the modern diamond-anvil cell for Raman scattering and other optical studies. He also advanced cryogenic pressure research, developing tunable low-temperature diamond-anvil cells, including an apparatus patented with R. J. Chen for far infrared magnetospectroscopy.