Picosecond strain dynamics in Ge${}_2$Sb${}_2$Te${}_5$ monitored by time-resolved x-ray diffraction

Abstract

Coherent phonons (CP) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, non-thermal switching in phase-change materials such as Ge${}_2$Sb${}_2$Te${}_5$(GST). Here we use ultrafast optical pump pulses to induce coherent acoustic phonons and stroboscopically measure the corresponding lattice distortions in GST using 100 ps x-ray pulses from the ESRF storage ring. A linear-chain model provides a good description of the observed changes in the diffraction signal, however, the magnitudes of the measured shifts are too large to be explained by thermal effects alone implying the presence of transient non-equilibrium electron heating in addition to temperature driven expansion. The information on the movement of atoms during the excitation process can lead to greater insight into the possibilities of using CP-induced phase-transitions in GST.

arXiv comment7 pages, 4 figures, Phys. Rev. B, in press

References in corpus (3)

• Ultrafast optical manipulation of atomic arrangements in chalcogenide alloy memory materials
• Laser-Induced Above-Bandgap Transparency in GaAs
• Polarization Dependent Optical Control of Atomic Arrangement in Multilayer Ge-Sb-Te Phase Change Materials

Cited by in corpus (5)

• Sub-nanometre resolution of atomic motion during electronic excitation in phase-change materials
• Photoinduced ultrafast transition of the local correlated structure in chalcogenide phase-change materials
• Insights into ultrafast Ge-Te bond dynamics in a phase-change superlattice
• Non-thermal transport of energy driven by photoexcited carriers in switchable solid states of GeTe
• Coherent gigahertz phonons in Ge${}_2$Sb${}_2$Te${}_5$ phase-change materials