Phonon damping in thin films of Fe

The phonon density of states (DOS) in thin films of polycrystalline α-Fe was measured by inelastic nuclear resonant scattering of synchrotron radiation. The thin-film DOS exhibits significant deviations from the DOS of bulk Fe, which we attribute to phonon lifetime broadening in the confined geometry. The measured DOS can be described with a damped harmonic oscillator model for the phonons with different quality factors Q=25(2)Q=25(2) and Q=13(1)Q=13(1) for layer thicknesses of 28 and 13 nm, respectively