Vibration Properties of Thin Films of Transition 3d-Metals on the Cu (111) Surface

Using the potentials, generated by a tight binding approximation, the equilibrium atomic structure and the phonon spectra of Cr and Ni thin films (one monolayer) deposited on the Cu (111) surface are calculated. The atomic relaxation, the vibrational state density distribution on the Cr, Ni and substrate atoms and the polarization of vibrational modes are considered. The change in the phonon spectrum during film deposition and the segregation of Cu atoms on the film surface are discussed. It is shown that mixing of the Cr and Ni atomic vibrations with those of the substrate takes place in the entire frequency range, resulting in a frequency shift of the vibrational modes of the substrate and the formation of new vibrational states not typical for a clean surface. The Cu/Cr/Cu and Cu/Ni/Cu structures are found to be more stable dynamically.