Phonon scattering and transmission at silicon-helium interfaces

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7003462

Olson, J R

Using a 2D thermal conductivity technique, the phonon scattering and transmission probabilities have been measured from 0.05K to 2.5K for silicon in contact with liquid [sup 4]He. For polished surfaces at low temperature, the diffuse scattering probability is less than 0.5%, and the classical Acoustic Mismatch Model of Khalatnikov correctly describes the observed transmission probability. At higher temperatures, the residual roughness of the surface causes additional diffuse phonon scattering which leads to enhanced transmission across the interface. Samples with thermal oxide films on the surfaces have additional diffuse scattering, which can be adequately described by assuming the films scatter phonons with the same probability as bulk a-SiO[sub 2]. Samples with either 60[angstrom] or 300[angstrom] Au films have diffuse scattering probabilities and transmission probabilities that are practically identical, confirming the hypothesis of Klitsner that thin Au films scatter phonons because of the [open quotes]mud-flat[close quotes] film morphology, a form of scattering that will not depend strongly on film thickness. The transmission probability is only 25-30% of that predicted by Diffuse Mismatch Model however, and this discrepancy has not been adequately explained. Samples with 2D Au diffraction gratings on them exhibited coherent resonant scattering of the phonons, but little phonon transmission. Samples which had been roughened by sandblasting or chemical etching had very high diffuse scattering probabilities, but the transmission probability for the sandblasted sample was much smaller than for the etched sample because of the subsurface damage caused the physical sandblasting process. Of the samples measured, only the etched sample showed a large transmission probability at low temperatures. Summarizing, the author has confirmed the veracity of the Acoustic Mismatch Model for the thermal boundary resistance at an ideal solid surface in contact with liquid helium.

• Research Organization: Cornell Univ., Ithaca, NY (United States)
• OSTI ID: 7003462
• Country of Publication: United States
• Language: English

Related Subjects

665000* -- Physics of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYOGENICS
ELEMENTS
ENERGY TRANSFER
EVEN-EVEN NUCLEI
HEAT TRANSFER
HELIUM 4
HELIUM ISOTOPES
INTERFACES
ISOTOPES
LIGHT NUCLEI
NUCLEI
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
SCATTERING
SEMIMETALS
SILICON
STABLE ISOTOPES
SURFACE PROPERTIES
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES