A simple and effective model of heat conduction across thin films is set up
and molecular dynamics simulations are implemented to explore the thermal
conductivity of nanoscale thin dielectric films in the direction perpendicu
lar to the film plane. Solid argon is selected as the model system due to i
ts reliable experimental data and potential function. Size effects of the t
hermal conductivity across thin films are found by computer simulations: in
a film thickness range of 2-10 nm, the conductivity values are remarkably
lower than the corresponding bulk experimental data and increase as the thi
ckness increases. The consistency between the approximate solution of the p
honon Boltzmann transport equation and the simulation results ascribes the
thermal conductivity size effect to the phonon scattering at film boundarie
s.