Phonon transport characteristics in a thin silicon film

Phonon transport characteristics in thin silicon film are investigated due to temperature disturbance at the film edges. Phonon intensity distribution ratio (I/^o_max, where I/^o_max is the maximum equilibrium intensity, I is the phonon intensity corresponding to acoustics branch at any location and time in the film) and phonon wavelength ratio, where k is the wavenumber, k = 2π/λ, and k_cutoff is the cutoff wavenum-ber based on the film length, kcutoff =2π/L) are introduced to assess the effects of quasi-ballistic and ballistic phonons on the film thermal conductivity and specific heat. It is found that phonon intensity ratio due to longitudinal acoustic branch is considerably higher than that of transverse acoustics branch. The influence of phonon wavelength ratio is not significantly high on the intensity ratio due to longitudinal acoustics branch. Reducing the wavelength ratio creates the size effect in the film while lowering thermal conductivity and specific heat of the film, which is more pronounced when the reduction becomes more than 20%.