Thermal conductivity of nanostructured SixGe1−x in amorphous limit by molecular dynamics simulation

Abstract

We report the thermal conductivity of amorphous SixGe1−x compound calculated versus composition and temperature. The result sets the minimum value of thermal conductivity which is achievable by nanostructuring. We employed molecular dynamics with Tersoff's potential for the calculations. It was found that, contrary to the crystalline SixGe1−x, the thermal conductivity of amorphous phase is a weak function of the material composition. For the most popular composition Si0.8Ge0.2, the thermal conductivity of the amorphous phase is less than 1 W m−1 K−1 with small reduction as the temperature increases from 300 K to 1400 K. The thermal conductivity of amorphous SixGe1−x for any value of x is approximately an order of magnitude smaller than the minimum thermal conductivity of crystalline SixGe1−x alloy, which occurs near x = 0.5. It is known that alloying with germanium is more efficient than nanostructuring to reduce the thermal conductivity of silicon; however, it was found that the amorphization process is even more effective than alloying for that purpose. It was also shown that the reduction of the thermal conductivity of silicon due to alloying with germanium is more efficient in crystalline phase than in amorphous phase.

Large-scale molecular dynamics investigation of geometrical features in nanoporous Si

“…6b, respectively), the HCACF behaviour is initially similar to the equivalent clustered systems (in brown for voids, and orange or cyan for pores), with the exception that there is a marked dip in the autocorrelation function after ~10 ps, corresponding to slightly anti-correlated behaviour in the heat-flux, and which reduces the thermal conductivity. This interesting effect is a characteristic of some liquid and amorphous materials [50][51][52], and could possibly be due to oscillatory behaviour in the HCACF resulting from ballistic phonons moving back and forth [53]. It is interesting that our results suggest that voids/pores materials exhibit anticorrelated heat-flux behaviour, suggesting liquid, amorphous, or oscillatory behaviour, which we will be investigating in future work.…”

Thermal transfer in amorphous superionic Li2S

“…1(b)-1(d)]. This behavior has been widely observed in other amorphous materials [30][31][32] because each atom has a distinct local environment as suggested by McGaughey and Kaviany [30]. The short time, i.e., around 0.5 ps, required by the HCACF to converge to zero eventually means that the scattering process among all the heat carriers will bring an equilibrium state during this period.…”

Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe–Mg2Si, SiGe–FeSi2

“…The thermal conductivities of the nanocomposites SiGe-FeSi 2 and SiGe-Mg 2 Si are lower than those of nanostructured SiGe and RTG SiGe. At room temperature, the thermal conductivity of the nanocomposite samples are similar to that of amorphous silicon, 33 which, as discussed, can be associated with the scattering of the acoustic phonons at interfaces of the silicide nanoinclusions. According to Mingo et al,…”