Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions

Abstract

We have developed an efficient scalable kernel method for thermal transport in open systems, with which we have computed the thermal conductance of a junction between bulk silicon and silicon nanowires with diameter up to 10 nm. We have devised scaling laws for transmission and reflection spectra, which allow us to predict the thermal resistance of bulk-nanowire interfaces with larger cross sections than those achievable with atomistic simulations. Our results indicate the characteristic size beyond which atomistic systems can be treated accurately by mesoscopic theories.

Highly sensitive thermal conductivity measurements of suspended membranes (SiN and diamond) using a 3ω-Völklein method

“…For instance the possibility of playing on the geometry of sample or on the nanostructuration of thin films to reduce the contribution of phonon to the thermal conductivity is a very active subject of research [2,7,8]; the reduced size of the studied objects requires specific experimental methods. Size effects are studied on the heat conduction (effect on the phonon mean free path [9], on the dispersion relation [10] or on the transmission coefficient [7,11]) and to mention only few in phononic crystals, nanoparticles embedded in a matrix, nanomembranes or in the presence of rough surfaces etc... Moreover especially for grown thin films, the thermal properties may strongly depend along which axis they are measured and therefore their measurements need adapted experimental techniques from high temperature [1] to low temperature [12].…”

Nanophononics: state of the art and perspectives

“…Even when recursive harmonic GF is used, the complexity of the calculation scales with the number of atoms per area like N 3 , thus preventing the applicability of this approach to systems with a cross-section larger than few nanometers. This limitation may be overcome by using the elastic scattering matrix approach [42], implemented with a partitioning-and-knitting algorithm, although applicable only in the case of short-range interactions [43]. Nevertheless the simulation of extended defects and of metal/insulator interfaces is still a formidable task.…”

Atomistic simulations of heat transport in real-scale silicon nanowire devices

“…1(a) and compared to the transmission spectrum of the interface between semiinfinite bulk and the semi-infinite SiNW. 31 We find that the transmission curves overlap for frequencies up to 4 THz regardless of the wire length ( Fig. 1), indicating that phonon transport at low frequency is ballistic.…”

“…Surprisingly, the transmission of the devices becomes larger than that of the semi-infinite wire 31 for acoustic frequencies larger than 4 THz. We observe that the total transmission may even exceed the number of available channels in the wire (see Fig.…”

“…25 We compute the thermal conductance of SiNW devices by harmonic lattice dynamics, [26][27][28][29][30] employing the scattering matrix approach. 31 This method permits the calculation of quantum thermal transport in open systems, yielding transmission spectra, thermal conductance, and real-space representation of heat flux and non-equilibrium energy density. The latter is obtained by computing the local density of states (LDOS) and allows us to probe different transport regimes.…”