The analysis of lattice thermal conductivity of nanowire

The lattice thermal conductivity of a semiconductor nanowire is a critical issue to improve the figure of merit of thermoelectric materials. The main purpose of this thesis is to re-establish a theory for calculating the axial lattice thermal conductivity of a semiconductor nanowire. The theory is based on the particle-concept. We use the relaxation time approximation to solve the Boltzmann’s equation, and take into account (i) the modification of the acoustic phonon dispersion due to spatial confinement, (ii) the change in the non-equilibrium phonon distribution due to partially diffuse boundary scattering, (iii)the frequency-dependence of the phonon group velocity, and(iv) the adoption of cutoff wave-vector in order to calculate the Debye temperature according to the modified phonon dispersion relation. From the analysis, we find that the lattice thermal conductivity is significantly reduced according to the decrease of the phonon group velocity, the phonon relaxation time, the Debye temperature, and the change in the non-equilibrium distribution. The solution of the thermal conductivity on the temperature, the boundary roughness, and the nanowire radius agree well with recent theoretical and experimental investigations.