Inelastic neutron-scattering measurements of the dispersion and width of transverse acoustic branches are reported for SixGe1-x, particularly for x=0.51. These alloys form high-quality single crystals. They are strongly disordered dynamically owing to the large Ge/Si mass ratio. This allows to study in function of disorder (x) the relations between the inhomogeneous broadening of acoustic waves, the Boson peak, and low-temperature thermal anomalies common to glasses. For x≤0.51 we find no boson peak, apparently no plateau in the thermal conductivity, but at large x a Rayleigh law on the phonon width, Γ∝Q4, where Q is the scattering vector.
- Acoustic branches
- Disordered crystals
- Thermal conductivity
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering