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 - TY - JOUR A1 - Herzog, Marc A1 - Bojahr, Andre A1 - Goldshteyn, J. A1 - Leitenberger, Wolfram A1 - Vrejoiu, I. A1 - Khakhulin, D. A1 - Wulff, M. A1 - Shayduk, Roman A1 - Gaal, P. A1 - Bargheer, Matias T1 - Detecting optically synthesized quasi-monochromatic sub-terahertz phonon wavepackets by ultrafast x-ray diffraction JF - Applied physics letters N2 - We excite an epitaxial SrRuO3 thin film transducer by a pulse train of ultrashort laser pulses, launching coherent sound waves into the underlying SrTiO3 substrate. Synchrotron-based x-ray diffraction (XRD) data exhibiting separated sidebands to the substrate peak evidence the excitation of a quasi-monochromatic phonon wavepacket with sub-THz central frequency. The frequency and bandwidth of this sound pulse can be controlled by the optical pulse train. We compare the experimental data to combined lattice dynamics and dynamical XRD simulations to verify the coherent phonon dynamics. In addition, we observe a lifetime of 130 ps of such sub-THz phonons in accordance with the theory. KW - acoustic waves KW - epitaxial layers KW - phonon dispersion relations KW - terahertz waves KW - thin film devices KW - X-ray diffraction Y1 - 2012 U6 - https://doi.org/10.1063/1.3688492 SN - 0003-6951 VL - 100 IS - 9 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Navirian, H. A1 - Shayduk, R. A1 - Leitenberger, Wolfram A1 - Goldshteyn, J. A1 - Gaal, P. A1 - Bargheer, Matias T1 - Synchrotron-based ultrafast x-ray diffraction at high repetition rates JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - We present a setup for ultrafast x-ray diffraction (UXRD) based at the storage ring BESSY II, in particular, a pump laser that excites the sample using 250 fs laser-pulses at repetition rates ranging from 208 kHz to 1.25 MHz. We discuss issues connected to the high heat-load and spatio-temporal alignment strategies in the context of a UXRD experiment at high repetition rates. The spatial overlap between laser pump and x-ray probe pulse is obtained with 10 mu m precision and transient lattice changes can be recorded with an accuracy of delta a/a(0) = 10(-6). We also compare time-resolved x-ray diffraction signals from a laser excited LSMO/STO superlattice with phonon dynamics simulations. From the analysis we determine the x-ray pulse duration to 120 ps in standard operation mode and below 10 ps in low-alpha mode. Y1 - 2012 U6 - https://doi.org/10.1063/1.4727872 SN - 0034-6748 VL - 83 IS - 6 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Gaal, P. A1 - Schick, Daniel A1 - Herzog, Marc A1 - Bojahr, Andre A1 - Shayduk, Roman A1 - Goldshteyn, J. A1 - Navirian, Hengameh A. A1 - Leitenberger, Wolfram A1 - Vrejoiu, Ionela A1 - Khakhulin, D. A1 - Wulff, M. A1 - Bargheer, Matias T1 - Time-domain sampling of x-ray pulses using an ultrafast sample response JF - Applied physics letters N2 - We employ the ultrafast response of a 15.4 nm thin SrRuO3 layer grown epitaxially on a SrTiO3 substrate to perform time-domain sampling of an x-ray pulse emitted from a synchrotron storage ring. Excitation of the sample with an ultrashort laser pulse triggers coherent expansion and compression waves in the thin layer, which turn the diffraction efficiency on and off at a fixed Bragg angle during 5 ps. This is significantly shorter than the duration of the synchrotron x-ray pulse of 100 ps. Cross-correlation measurements of the ultrafast sample response and the synchrotron x-ray pulse allow to reconstruct the x-ray pulse shape. Y1 - 2012 U6 - https://doi.org/10.1063/1.4769828 SN - 0003-6951 VL - 101 IS - 24 PB - American Institute of Physics CY - Melville ER -