7 research outputs found
Thermoelastic study of nanolayered structures using time-resolved x-ray diffraction at high repetition rate
We investigate the thermoelastic response of a nanolayered sample composed of
a metallic SrRuO3 (SRO) electrode sandwiched between a ferroelectric
Pb(Zr0.2Ti0.8)O3 (PZT) film with negative thermal expansion and a SrTiO3
substrate. SRO is rapidly heated by fs-laser pulses with 208 kHz repetition
rate. Diffraction of x-ray pulses derived from a synchrotron measures the
transient out-of-plane lattice constant c of all three materials simultaneously
from 120 ps to 5 mus with a relative accuracy up to Delta c/c = 10^-6. The
in-plane propagation of sound is essential for understanding the delayed out of
plane expansion.Comment: 5 pages, 3 figure
Investigation of Cu poor and Cu rich Cu In,Ga Se2 CdS interfaces using hard X ray photoelectron spectroscopy
Cu poor and Cu rich Cu In,Ga Se2 CIGSe absorbers were used as substrates for the chemical bath deposition of ultrathin CdS buffer layers in the thickness range of a few nanometers in order to make the CIGSe CdS interface accessible by hard X ray photo emission spectroscopy. The composition of both, the absorber and the buffer layer as well as the energetics of the interface was investigated at room temperature and after heating the samples to elevated temperatures 200 C, 300 C and 400 C . It was found that the amount of Cd after the heating treatment depends on the near surface composition of the CIGSe absorber. No Cd was detected on the Cu poor surface after the 400 C treatment due to its diffusion into the CIGSe layer. In contrast, Cd was still present on the Cu rich surface after the same treatment at 400
Thermoelastic study of nanolayered structures using time-resolved X-ray diffraction at high repetition rate
Direct time domain sampling of subterahertz coherent acoustic phonon spectra in SrTiO3 using ultrafast x ray diffraction
We synthesize sub-THz longitudinal quasi-monochromatic acoustic phonons in a
SrTiO single crystal using a SrRuO/SrTiO superlattice as an
optical-acoustic transducer. The generated acoustic phonon spectrum is
determined using ultrafast X-ray diffraction. The analysis of the generated
phonon spectrum in the time domain reveals a k-vector dependent phonon
lifetime. It is observed that even at sub-THz frequencies the phonon lifetime
agrees with the 1/ power law known from Akhiezer's model for hyper
sound attenuation. The observed shift of the synthesized spectrum to the higher
is discussed in the framework of non-linear effects appearing due to the
high amplitude of the synthesized phonons
Feasibility of Valence-to-Core X-ray Emission Spectroscopy for Tracking Transient Species
X-ray spectroscopies, when combined in laser-pump, X-ray-probe measurement schemes, can be powerful tools for tracking the electronic and geometric structural changes that occur during the course of a photoinitiated chemical reaction. X-ray absorption spectroscopy (XAS) is considered an established technique for such measurements, and X-ray emission spectroscopy (XES) of the strongest core-to-core emission lines (Kα and Kβ) is now being utilized. Flux demanding valence-to-core XES promises to be an important addition to the time-resolved spectroscopic toolkit. In this paper we present measurements and density functional theory calculations on laser-excited, solution-phase ferrocyanide that demonstrate the feasibility of valence-to-core XES for time-resolved experiments. We discuss technical improvements that will make valence-to-core XES a practical pump–probe technique