Transient lattice distortion induced by ultrashort heat pulse propagation through thin film metal/metal interface

Abstract

Phonon propagation across the Cu/Ag(111) interface and transient structural disorder in Ag(111) crystal, after excitation of 18 nm copper layer with UV femtosecond pulses has been studied by means of picosecond time resolved X-ray diffraction. The lattice disorder was measured by the changes in peak shift and broadening of the XRD rocking curve. A blast force was formed within 2 ps after fs UV irradiation. After fast initial expansion and contraction, a sharp oscillation is observed, while the subsequent oscillations were found to be broader due to out-of phase relationship between the sound waves in the copper and silver layers.