Diffuse scattering from surface phonons
Nanoscale surface phonons, produced by an ultrafast infrared pump on several different samples, are studied in the time domain by spectroscopy of diffuse scattering of an extreme ultraviolet FEL probe. It's a simple and effective method to generate and measure coherent surface phonons propagating in all directions and spanning a wavelength range from 60 to 300 nm.
Capotondi et al., Physical Review Letters, Vol. 135 - 26, p. 266101 (2025)..
|
This phenomenon is observed on a variety of samples, including single-layer and multilayer metal films, as well as bulk semiconductors. The measured surface phonon dispersions show good agreement with theoretical calculations. By comparing signal amplitudes from samples with different surface morphologies, we find that the excitation mechanism is linked to the natural surface roughness of the samples. However, the signal is still detectable on extremely smooth surfaces with subnanometer roughness. At each point on the detector, the diffuse scattering intensity exhibits oscillations at well-defined frequencies that correspond to surface phonons with wave vectors determined by the scattering geometry. |
A Fourier transform of the radial average of the intensity projection on the reciprocal space gives surface phonon dispersion values in good agreement with theoretical calculations. Retrieve articleTime-Domain Extreme-Ultraviolet Diffuse Scattering Spectroscopy of Nanoscale Surface Phonons.
Capotondi F., Maznev A. A., Bencivenga F., Bonetti S., Engel D., Fainozzi D., Fausti D., Foglia L., Gutt C., Jaouen N., Ksenzov D., Masciovecchio C., Nelson K. A., Nikolov I., Pancaldi M., Pedersoli E., Pfau B., Raimondi L., Romanelli F., Totani R., Trigo M. DOI: 10.1103/dq8w-62bm |
