Acoustic phonons in InSb probed by time‐resolved X‐ray diffraction

Abstract

Acoustical phonons in InSb were induced with femtosecond light pulses and probed by diffraction of ultrashort X-ray pulses in the crystal lattice. The time dependent transient X-ray diffraction signal due to elastic lattice deformation was measured with subpicosecond resolution. The elastic lattice deformation depends on the temporal evolution of the energy transfer from excited electrons in the semiconductor into the lattice. As already shown in previous investigation a conventional thermoelastic model is not sufficient to describe this coupling process. Here a complex simulation including a two temperature model of the electron and lattice as well as the microscopic behavior of the electron plasma is applied to explain important effects like thermal carrier diffusion and band gap deformation found in the lattice deformation experiments. When this model is used, with realistic values for both pump laser fluences and bulk material constants, excellent agreement between the experimentally observed time dependent lattice deformation and calculated values is obtained throughout the observation period.

Comparing the oscillation phase in optical pump-probe spectra to ultrafast x-ray diffraction in the metal-dielectric SrRuO3/SrTiO3superlattice

“…In the case of bulk semiconductors UXRD allowed conclusions to be drawn on modifications of the strain fronts induced by the fast diffusion of hot carriers. [1][2][3] For bulk bismuth UXRD in combination with ab initio simulations revealed how the lattice potential changes with the time-dependent carrier density. 4 UXRD and ultrafast electron-diffraction studies show that, for increasing excitation fluence, electronic pressure gains importance versus phonon pressure in metallic systems.…”

Excitation of longitudinal and transverse coherent acoustic phonons in nanometer free-standing films of (001) Si

“…In this scheme, the optical probe pulse is replaced by an electron ͑or an x ray͒ pulse, which probes displacements in the periodic structure at the atomic level by diffracting off the sample. In this context, several time resolved electron 9 and x-ray [10][11][12][13][14][15][16] experiments demonstrated the excitation and detection of longitudinal coherent acoustic phonons in thin films and superlattice structures. However, to date, it has not been possible to resolve the transverse-acoustic components primarily due to signal-to-noise limitations.…”

Communication: The formation of rarefaction waves in semiconductors after ultrashort excitation probed by grazing incidence ultrafast time-resolved x-ray diffraction

“…Both steps are solved by time and space dependent differential equations. Due to the experimental conditions, the physical problems are treated one-dimensional in space 23 . Third, the diffraction signal was calculated using the dynamical diffraction theory of the deformed crystals 28 .…”