Hydrostatic pressure effects on the processes of lattice thermal conductivity of bulk Silicon and nanowires

摘要

The lattice thermal conductivity (LTC) of silicon nanowires (NWs) with diameters of 115, 56, 37 and 22 nm in the temperature range of 2–300 K for different pressures ranging from 0 to 10 GPa, was calculated by employing a modified Callaway model. Both longitudinal and transverse modes were explicitly considered within the model. A strategy is utilized to calculate the Debye and phonon group velocity in addition to the bulk modulus and it is derivative for different NW diameters from their related melting temperature under different pressures. The influence of the Gruneisen parameter, surface roughness and dislocation as structurally dependent parameters are successfully exploited to correlate the calculated values of LTC to that of the experimentally measured curves at various pressures including zero. The respective application of the Murnghan and Clapeyron equations for pressure-dependent lattice volume and melting temperature in the Callaway model produces results that tend to be systematically applicable by this model. The confinement and size effects of phonons and the role of pressure in the reduction of LTC are investigated. The peak value of LTC decreases with the increase of pressure for both bulk and its nanowires.