TY - JOUR
T1 - Thermal phonons and defects in semiconductors
T2 - The physical reason why defects reduce heat flow, and how to control it
AU - Estreicher, S. K.
AU - Gibbons, T. M.
AU - Bebek, M. B.
N1 - Publisher Copyright:
© 2015 AIP Publishing LLC.
PY - 2015/3/21
Y1 - 2015/3/21
N2 - It is generally accepted that heat-carrying phonons in materials scatter off each other (normal or Umklapp scattering) as well as off defects. This assumes static defects, implies quasi-instantaneous interactions and at least some momentum transfer. However, when defect dynamics are explicitly included, the nature of phonon-defect interactions becomes more subtle. Ab initio microcanonical molecular-dynamics simulations show that (1) spatially localized vibrational modes (SLMs), associated with all types of defects in semiconductors, can trap thermal phonons; (2) the vibrational lifetimes of excitations in SLMs are one to two orders of magnitude longer (dozens to hundreds of periods of oscillation) than those of bulk phonons of similar frequency; (3) it is phonon trapping by defects (in SLMs) rather than bulk phonon scattering, which reduces the flow of heat; and (4) the decay of trapped phonons and therefore heat flow can be predicted and controlled - at least to some extent - by the use of carefully selected interfaces and δ layers.
AB - It is generally accepted that heat-carrying phonons in materials scatter off each other (normal or Umklapp scattering) as well as off defects. This assumes static defects, implies quasi-instantaneous interactions and at least some momentum transfer. However, when defect dynamics are explicitly included, the nature of phonon-defect interactions becomes more subtle. Ab initio microcanonical molecular-dynamics simulations show that (1) spatially localized vibrational modes (SLMs), associated with all types of defects in semiconductors, can trap thermal phonons; (2) the vibrational lifetimes of excitations in SLMs are one to two orders of magnitude longer (dozens to hundreds of periods of oscillation) than those of bulk phonons of similar frequency; (3) it is phonon trapping by defects (in SLMs) rather than bulk phonon scattering, which reduces the flow of heat; and (4) the decay of trapped phonons and therefore heat flow can be predicted and controlled - at least to some extent - by the use of carefully selected interfaces and δ layers.
UR - http://www.scopus.com/inward/record.url?scp=84925002595&partnerID=8YFLogxK
U2 - 10.1063/1.4913826
DO - 10.1063/1.4913826
M3 - Article
AN - SCOPUS:84925002595
VL - 117
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 11
M1 - 112801
ER -