Paper published AND recipient of a NDSEG Fellowship: CONGRATS JEFF

Jeff Braun recently was awarded a NDSEG Fellowship to support his PhD work.  At the time of the announcement of this award, Jeff’s paper that experimentally demonstrates the size effects on the thermal conductivity of amorphous silicon appeared in Physical Review B (Phys. Rev. B 93, 140201(R) (2016)).  CONGRATS JEFF!!!!!!

Abstract of Paper

We investigate thickness-limited size effects on the thermal conductivity of amorphous silicon thin films ranging from 3 to 1636 nm grown via sputter deposition. While exhibiting a constant value up to 100 nm, the thermal conductivity increases with film thickness thereafter. The thickness dependence we demonstrate is ascribed to boundary scattering of long wavelength vibrations and an interplay between the energy transfer associated with propagating modes (propagons) and nonpropagating modes (diffusons). A crossover from propagon to diffuson modes is deduced to occur at a frequency of 1.8 THz via simple analytical arguments. These results provide empirical evidence of size effects on the thermal conductivity of amorphous silicon and systematic experimental insight into the nature of vibrational thermal transport in amorphous solids.

This work was funded by ONR Grant No. N00014-15-12769.

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