Bjorn Vermeersch
Purdue University
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Publication
Featured researches published by Bjorn Vermeersch.
Physical Review B | 2015
Bjorn Vermeersch; Jesús Carrete; Natalio Mingo; Ali Shakouri
Semiconductor alloys exhibit a strong dependence of effective thermal conductivity on measurement frequency. So far this quasi-ballistic behaviour has only been interpreted phenomenologically, providing limited insight into the underlying thermal transport dynamics. Here, we show that quasi-ballistic heat conduction in semiconductor alloys is governed by Levy superdiffusion. By solving the Boltzmann transport equation (BTE) with ab initio phonon dispersions and scattering rates, we reveal a transport regime with fractal space dimension
Physical Review B | 2015
Bjorn Vermeersch; Amr M. S. Mohammed; Gilles Pernot; Yee Rui Koh; Ali Shakouri
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Applied Physics Letters | 2016
Bjorn Vermeersch; Jesús Carrete; Natalio Mingo
and cumulative conductivity spectra
Nano Letters | 2014
Tela Favaloro; Joonki Suh; Bjorn Vermeersch; Kai Liu; Yijia Gu; Long-Qing Chen; Kevin Wang; J. Wu; Ali Shakouri
kappa_{Sigma}(tau;Lambda)sim (tau;Lambda)^{gamma}
Journal of Applied Physics | 2013
Bjorn Vermeersch; Je-Hyeong Bahk; James Christofferson; Ali Shakouri
resolved for relaxation times or mean free paths through simple relations
Computer Physics Communications | 2017
Jesús Carrete; Bjorn Vermeersch; Ankita Katre; Ambroise van Roekeghem; Tao Wang; Georg K. H. Madsen; Natalio Mingo
alpha = 3-beta = 1 + 3/n = 2 - gamma
Nano Letters | 2015
Amr M. S. Mohammed; Yee Rui Koh; Bjorn Vermeersch; Hong Lu; Peter G. Burke; A. C. Gossard; Ali Shakouri
. The quasi-ballistic transport inside alloys is no longer governed by Brownian motion, but instead dominated by Levy dynamics. This has important implications for the interpretation of thermoreflectance (TR) measurements with modified Fourier theory. Experimental
Journal of Applied Physics | 2016
Bjorn Vermeersch
alpha
semiconductor thermal measurement and management symposium | 2011
S. Alavi; Kazuaki Yazawa; Glenn Alers; Bjorn Vermeersch; James Christofferson; Ali Shakouri
values for InGaAs and SiGe, determined through TR analysis with a novel Levy heat formalism, match ab initio BTE predictions within a few percent. Our findings lead to a deeper and more accurate quantitative understanding of the physics of nanoscale heat flow experiments.
Applied Physics Letters | 2016
Yee Rui Koh; MohammadAli Shirazi-HD; Bjorn Vermeersch; Amr M. S. Mohammed; J. Shao; Gilles Pernot; Je-Hyeong Bahk; Michael J. Manfra; Ali Shakouri
evy dynamics with fractal dimension α< 2. Here, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure L´ evy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any “effective” thermal parameters and without any ap rioriknowledge of microscopic phonon scattering mechanisms. Identified α values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal L´ evy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.