V.V. Aleksandrov

New data concerning surface Mandelstamm-Brillouin light scattering from the basal plane of germanium crystal

Abstract The intensity of Mandelstamm-Brillouin satellites (MBS) corresponding to leaky surface waves (LSW) was rigistered for Ge crystal of z -cut. The intensity was found to reach its largest values for two orientations of the light scattering plane: first, when the plane was parallel to [110], and second, when parallel to [cos 35°, sin 35°, 0]. A broad additional surface spectral line located at a frequency ≈ 1.4 times higher than those of MBS related to generalized surface waves and LSW was detected.

Mandelstamm-Brillouin studies of peculiarities of the phonon frequency distribution at cubic crystal (001) surfaces

Abstract For z -cut cubic crystals of Si, GaAs, InSb measurements of the peak intensities of Mandelstamm-Brillouin satellites corresponding to surface excitations of the pseudo surface mode (PSM) frequency range were conducted. The angular intensity dependence for various plane of incidence orientations reveal two maxima, for θ 2 =45°, and for θ 2 =36° ( Si ), 33° (GaAs), and 32° (InSb). Here θ is the angle between the (010) plane and the plane of incidence of light. The variations of the PSM satellite linewidth registered experimentally for the first time demonstrate the positions of its minima to be well correlated with θ 1,2 in all the cases. The non-monotonous peak intensity and the linewidth of the PSM satellite behavior are explained by PSM attenuation anomalies around θ 1,2 .

Observation of surface Mandelstamm-Brillouin light scattering spectra in high-temperature superconducting YBa2Cu3O7-° and La2-xSrxCuO4-δ single crystals and surface wave velocity determination

Abstract Observations of light scattering spectra caused by thermally excited surface Rayleigh waves in YBa2Cu3O7-δ and La2-xSrxCuO4-δ high Tc superconducting single crystals are reported. Surface wave velocities are obtained from the Brillouin line frequency shifts at room temperature.

Surface Mandelstamm-Brillouin light scattering from basal plane of germanium crystal

Abstract Mandelstamm-Brillouin (MB) surface light scattering spectra of z-cut cubic crystal of Ge are experimentally studied. Simultaneous observations of MB satellites caused by generalized surface waves and pseudo-surface “leaky” waves are reported.

Anisotropy of Rayleigh wave velocity of TmBa2Cu3O7−y single crystals

Abstract The Rayleigh waves velocities and their anisotropy were studied in both untwinned, twinned TmBa 2 Cu 3 O 7−y orthorhombic crystals and in tetragonal ones. The experiments were performed at room temperature.

Brillouin scattering study of the pseudosurface acoustic mode on the (110) face of cubic crystals having elastic anisotropy ratio above unity

We report the experimental observation of a pseudosurface mode in (110)‐cut cubic crystals having the anisotropy ratio η=2C44/(C11−C12)≳1, where C11, C12, and C44 are elastic constants. The measurements have been performed with Brillouin light‐scattering spectroscopy for GaAs, InSb, Ge, and InAs crystals. Results are shown for GaAs and InSb. An additional Brillouin satellite has been observed in the bulk velocity range for general propagation directions on the (110) plane; this peak is attributed to the presence of the pseudosurface mode. For all the crystals investigated, we have found that the pseudosurface mode exists for propagation directions within the range θ=±55°, where θ is the azimuthal angle measured from the [001] crystal axis. The results of calculations of the light‐scattering cross section and of the propagation velocity of the pseudosurface mode are in a good agreement with the measurements.

Determination of rayleigh wave velocities in high Tc superconducting RBa2Cu3O7−y (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm, Yb) single crystals by Mandelstamm-Brillouin light scattering spectra

Abstract We obtained Rayleigh wave velocities in rare earth cuprate crystals in both orthorhombic and tetragonal phases at room temperature. Rayleigh wave velocity in superconducting samples was shown to be varied from 2.1 to 2.3 km/s in connection with cation R radius. The annealing of the crystals under oxygen flow at 450 °C produced 3–6% velocity increase. Tetragonal samples velocity values were found to be 10–15% lower the ones in orthorhombic modified crystals.

Bi-based superconductors and their surface wave velocities

Abstract We have measured the surface hypersound velocity values VR of Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 single crystals by Mandelstamm-Brillouin light scattering spectra. Measurements were performed at room temperature. In case of Bi2Sr2CaCu2O8 crystal considerable difference (20%) of (001) plane VR values along a and b crystallographic directions was manifested. However mentioned VR anisotropy in Bi2Sr2CuO6 crystals was not observed.

Comparative study of hypersonic dynamics in CaF2 and SrF2 films on Si(111)

CaF2 and SrF2 films grown on Si(111) by molecular beam epitaxy were studied by the Brillouin spectroscopy method. The measured velocities of surface acoustic waves are in close agreement with those calculated with a simple model of a layered structure. The only discrepancy was a decrease of the velocity in CaF2 films of about 100 nm thick: this was attributed to the difference of the growth modes at the beginning of CaF2 and SrF2 epitaxy on Si(111).

Studies of Mandelstamm-Brillouin light scattered by the surface of (111)-, (110)-cutted GaAs, and (111)-cutted InSb crystals

Abstract Mandelstamm-Brillouin (MB) surface light scattering spectra of light in case of GaAs crystals of (111) and (110) cut demonstrate considerable drop of the intensity of the spectral components caused as by Generalized Surface Wave (GSW), as by High Frequency Pseudo Surface Mode (HFPSM), incident light wave polarization being changed from parallel to normal to the plane of light incidence. New MB peak located at 11.8 GHz was detected for (110) plane scattering. In case of InSb crystal of (111) cut simultaneous registration of MB satellites corresponding to GSW and to Pseudo Surface Mode is reported.