In situ Brillouin spectroscopy of a pressure-induced apparent second-order transition in a silicate glass.

Brillouin scattering measurements of a silicate glass, carried out at high pressures in the diamond anvil cell, show a dramatic increase in the pressure dependence of longitudinal velocity, and a discontinuity in the compressibility of the glass at about 6 GPa. While a first-order phase transition has been documented under pressure within amorphous ice, we demonstrate that an apparent second-order transition to a new, structurally distinct amorphous phase can occur via the abrupt onset of a new compressional mechanism, which may be triggered by a shift in polymerization of the glass or an onset of a change in coordination of silicon, within pressurized amorphous silicates.

Raman and Brillouin scattering spectroscopy studies of atomic layer-deposited ZrO(2) and HfO(2) thin films.

Atomic layer-deposited ZrO(2) (zirconia) and HfO(2) (hafnia) films with various thicknesses, ranging from 112 to 660 nm, have been studied by Raman scattering spectroscopy. Spectral analysis of the excellent quality Raman data obtained by using freestanding edges of the films has unambiguously demonstrated that a metastable tetragonal t-ZrO(2) is coexisting with the stable monoclinic phase in zirconia films. Even though the Raman spectrum signal-to-noise ratio was high, only the monoclinic phase was positively identified from the observed spectral patterns of hafnia films. X-ray diffraction patterns are used to define the structure of metastable phases. Complementary Brillouin light scattering measurements of the freestanding edges are also employed in constraining elastic properties of the 405 nm HfO(2) thin film.