TY  - JOUR
A1  - Schick, Daniel
A1  - Bojahr, Andre
A1  - Herzog, Marc
A1  - von Korff Schmising, Clemens
A1  - Shayduk, Roman
A1  - Leitenberger, Wolfram
A1  - Gaa, P.
A1  - Bargheer, Matias
T1  - Normalization schemes for ultrafast x-ray diffraction using a table-top laser-driven plasma source
JF  - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques
N2  - We present an experimental setup of a laser-driven x-ray plasma source for femtosecond x-ray diffraction. Different normalization schemes accounting for x-ray source intensity fluctuations are discussed in detail. We apply these schemes to measure the temporal evolution of Bragg peak intensities of perovskite superlattices after ultrafast laser excitation.
Y1  - 2012
U6  - https://doi.org/10.1063/1.3681254
SN  - 0034-6748
VL  - 83
IS  - 2
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Bojahr, Andre
A1  - Schick, Daniel
A1  - Märten, Lena
A1  - Herzog, Marc
A1  - Vrejoiu, Ionela
A1  - von Korff Schmising, Clemens
A1  - Milne, Chris
A1  - Johnson, Steven Lee
A1  - Bargheer, Matias
T1  - Comparing the oscillation phase in optical pump-probe spectra to ultrafast x-ray diffraction in the metal-dielectric SrRuO3/SrTiO3 superlattice
JF  - Physical review : B, Condensed matter and materials physics
N2  - We measured the ultrafast optical response of metal-dielectric superlattices by broadband all-optical pump-probe spectroscopy. The observed phase of the superlattice mode depends on the probe wavelength, making assignments of the excitation mechanism difficult. Ultrafast x-ray diffraction data reveal the true oscillation phase of the lattice which changes as a function of the excitation fluence. This result is confirmed by the fluence dependence of optical transients. We set up a linear chain model of the lattice dynamics and successfully simulated the broadband optical reflection by unit-cell resolved calculation of the strain-dependent dielectric functions of the constituting materials.
Y1  - 2012
U6  - https://doi.org/10.1103/PhysRevB.85.224302
SN  - 1098-0121
VL  - 85
IS  - 22
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Herzog, Marc
A1  - Schick, Daniel
A1  - Gaal, P.
A1  - Shayduk, Roman
A1  - von Korff Schmising, Clemens
A1  - Bargheer, Matias
T1  - Analysis of ultrafast X-ray diffraction data in a linear-chain model of the lattice dynamics
JF  - Applied physics : A, Materials science & processing
N2  - We present ultrafast X-ray diffraction (UXRD) experiments which sensitively probe impulsively excited acoustic phonons propagating in a SrRuO3/SrTiO3 superlattice and further into the substrate. These findings are discussed together with previous UXRD results (Herzog et al. in Appl. Phys. Lett. 96, 161906, 2010; Woerner et al. in Appl. Phys. A 96, 83, 2009; v. Korff Schmising in Phys. Rev. B 78, 060404(R), 2008 and in Appl. Phys. B 88, 1, 2007) using a normal-mode analysis of a linear-chain model of masses and springs, thus identifying them as linear-response phenomena. We point out the direct correspondence of calculated observables with X-ray signals. In this framework the complex lattice motion turns out to result from an interference of vibrational eigenmodes of the coupled system of nanolayers and substrate. UXRD in principle selectively measures the lattice motion occurring with a specific wavevector, however, each Bragg reflection only measures the amplitude of a delocalized phonon mode in a spatially localized region, determined by the nanocomposition of the sample or the extinction depth of X-rays. This leads to a decay of experimental signals although the excited modes survive.
Y1  - 2012
U6  - https://doi.org/10.1007/s00339-011-6719-z
SN  - 0947-8396
VL  - 106
IS  - 3
SP  - 489
EP  - 499
PB  - Springer
CY  - New York
ER  -