Phonon transmission at Si/Ge and polytypic Ge interfaces using full-band mismatch based models

Abstract

This paper presents theoretical investigations on the interfacial thermal conductance (Kapitza conductance) in both monotype Si/Ge (cubic 3C) and polytype (cubic 3C / hexagonal 2H) Ge interfaces by using Full Band extensions of Diffusive (DMM) and Acoustic (AMM) Mismatch Models. In that aims, phonon dispersions in the Full 3D Brillouin Zone have been computed via an atomistic adiabatic bond charge model. The effects of crystal orientation are investigated and the main phonon modes involved in heat transfer are highlighted. According to our calculations, polytype interfaces without any mass mismatch but with a crystallographic phase mismatch exhibit a thermal conductance very close to that of Si/Ge interfaces with a mass mismatch but without any phase mismatch. Besides, the orientations of Ge polytype interface that have been observed experimentally in nanowires, i.e. along   / 5051  , exhibit the lowest interfacial conductance and thus may offer new opportunities for nanoscale thermoelectric applications.

Full Band Monte Carlo simulation of phonon transfer at interfaces

“…Thus, Gint appears to be equal to 243.3±41.9 MW/m 2 independently of the device length. This is consistent with the DMM theory which predicts a unique value for the Si/Ge interface conductance of 225 MW/m 2 /K [22]. The modification of the transport regime of phonon in the studied length range does not affect Gint.…”

“…When a particle collides with a semi-transparent interface, both elastic and diffusive mechanisms are considered. Besides, the probability of transmission of a phonon colliding the interface is obtained within the Full-Band Diffusive Mismatch Model (DMM) [22]. In this model, the interface is assumed to have many defects so that each phonon colliding the interface loses totally the memory of its initial state.…”

Si and Ge allotrope heterostructured nanowires: experimental evaluation of the thermal conductivity reduction

“…Finally, the NW thermal resistance R NW is constituted of 3 series resistances: the 2H domain thermal resistance, the 3C domain thermal resistance and the polytype interface 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t 19 resistance. Using the 23 W/m.K 2H thermal conductivity predicted in [10] and the the λ 3C measured on the 500°C annealed sample, we can hence estimate the polytype interface conductance in the range of 150-400 MW/m 2 .K, in good accordance with the order of magnitude of the conductance identified in [11] by theoretical investigations.…”

“…For 3ω-SThM scanning, the surface of the sample constituted of embedded NWs in silica is planarized using a chemical mechanical polishing (CMP) process with a colloidal silica suspension. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t In [11], the authors have presented theoretical investigations on the interfacial thermal conductance in polytype 3C/2H Ge interfaces. Using ABCM (adiabatic bond charge model), they studied the effects of the crystal orientation and of the main phonon modes involved in heat transfer.…”

Study of Phonon Transport Across Si/Ge Interfaces Using Full-Band Phonon Monte Carlo Simulation

“…For an incident phonon of wave vector and angular frequency colliding with this interface from the A-side, the spectral transmission probability → ( ) is given by [43]:…”