The confinement of materials in low-dimensional structures has significant impact on propagating excitations like phonons. Using the isotope-specific Fe57 nuclear resonant vibrational spectroscopy we were able to determine elastic and thermodynamic properties of ultrathin Fe films on W(110). With decreasing thickness one observes a significant increase of the mean atomic displacement that goes along with an enhancement of vibrational modes at low energies as compared to the bulk. The analysis reveals that these deviations result from atomic vibrations of the single atomic layers at the two boundaries of the film, while the atoms inside the films vibrate almost bulklike.
Physical Review Letters
- Pub Date:
- November 2007
- Phonons or vibrational states in low-dimensional structures and nanoscale materials;
- Surface and interface dynamics and vibrations;
- Mossbauer effect;
- other gamma-ray spectroscopy