TY - JOUR
T1 - Femtosecond structural transformation of phase-change materials far from equilibrium monitored by coherent phonons
AU - Hase, Muneaki
AU - Fons, Paul
AU - Mitrofanov, Kirill
AU - Kolobov, Alexander V.
AU - Tominaga, Junji
N1 - Funding Information:
This work was supported by the X-ray Free Electron Laser Priority Strategy Program (Nos 12013011 and 12013023) from the Ministry of Education, Culture, Sports, Science and Technology of Japan), and by CREST, Japan Science and Technology Agency.
Publisher Copyright:
© 2015 Macmillan Publishers Limited. All rights reserved.
PY - 2015/9/25
Y1 - 2015/9/25
N2 - Multicomponent chalcogenides, such as quasi-binary GeTe-Sb 2 Te 3 alloys, are widely used in optical data storage media in the form of rewritable optical discs. Ge 2 Sb 2 Te 5 (GST) in particular has proven to be one of the best-performing materials, whose reliability allows more than 10 6 write-erase cycles. Despite these industrial applications, the fundamental kinetics of rapid phase change in GST remain controversial, and active debate continues over the ultimate speed limit. Here we explore ultrafast structural transformation in a photoexcited GST superlattice, where GeTe and Sb 2 Te 3 are spatially separated, using coherent phonon spectroscopy with pump-pump-probe sequences. By analysing the coherent phonon spectra in different time regions, complex structural dynamics upon excitation are observed in the GST superlattice (but not in GST alloys), which can be described as the mixing of Ge sites from two different coordination environments. Our results suggest the possible applicability of GST superlattices for ultrafast switching devices.
AB - Multicomponent chalcogenides, such as quasi-binary GeTe-Sb 2 Te 3 alloys, are widely used in optical data storage media in the form of rewritable optical discs. Ge 2 Sb 2 Te 5 (GST) in particular has proven to be one of the best-performing materials, whose reliability allows more than 10 6 write-erase cycles. Despite these industrial applications, the fundamental kinetics of rapid phase change in GST remain controversial, and active debate continues over the ultimate speed limit. Here we explore ultrafast structural transformation in a photoexcited GST superlattice, where GeTe and Sb 2 Te 3 are spatially separated, using coherent phonon spectroscopy with pump-pump-probe sequences. By analysing the coherent phonon spectra in different time regions, complex structural dynamics upon excitation are observed in the GST superlattice (but not in GST alloys), which can be described as the mixing of Ge sites from two different coordination environments. Our results suggest the possible applicability of GST superlattices for ultrafast switching devices.
UR - http://www.scopus.com/inward/record.url?scp=84942694024&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84942694024&partnerID=8YFLogxK
U2 - 10.1038/ncomms9367
DO - 10.1038/ncomms9367
M3 - Article
AN - SCOPUS:84942694024
SN - 2041-1723
VL - 6
JO - Nature Communications
JF - Nature Communications
M1 - 8367
ER -