Thermal conductivity of nanostructured SixGe12x in amorphous limit by molecular dynamics simulation

We report the thermal conductivity of amorphous SixGe1x 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 SixGe1x, 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 1W m1 K1 with small reduction as the temperature increases from 300K to 1400 K. The thermal conductivity of amorphous SixGe1x for any value of x is approximately an order of magnitude smaller than the minimum thermal conductivity of crystalline SixGe1x alloy, which occurs near x¼0.5. 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.

Thermal conductivity, Molecular dynamics