Size-dependent model for thin film and nanowire thermal conductivity

We present an analytical model for the size-dependence of thin film and nanowirethermal conductivity and compare the predictions to experimental measurements on siliconnanostructures. The model contains no fitting parameters and only requires the bulk lattice constant, bulk thermal conductivity, and an acoustic phonon speed as inputs. By including the mode-dependence of the phonon lifetimes resulting from phonon-phonon and phonon-boundary scattering, the model captures the approach to the bulk thermal conductivity of the experimental data better than gray models based on a single lifetime.