TY - JOUR
T1 - All-Optical Detection of Periodic Structure of Chalcogenide Superlattice Using Coherent Folded Acoustic Phonons
AU - Suzuki, Takara
AU - Saito, Yuta
AU - Fons, Paul
AU - Kolobov, Alexander V.
AU - Tominaga, Junji
AU - Hase, Muneaki
N1 - Funding Information:
This work was supported by Core Research for Evolutional Science and Technology (CREST) (NO. JPMJCR14F1), JST, Japan. The authors acknowledge Ms. R. Kondou for sample preparation.
Publisher Copyright:
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2018/9
Y1 - 2018/9
N2 - Chalcogenide superlattices (SL) consist of alternately stacked GeTe and Sb2Te3 layers. The structure can act as a 3D topological insulator depending on the constituent layer thicknesses, making the design of the SL period a central issue for advancing chalcogenide SL as potential candidates for spin devices as well as for optimization of the current generation of phase-change memory devices. Here we explore the periodic structure of chalcogenide SL by observing coherent folded longitudinal acoustic (FLA) phonons excited by femtosecond laser pulse irradiation. The peak frequency of the FLA modes is observed to change upon variation of the thickness of the GeTe layer, which is well reproduced by means of an elastic continuum model. In addition, a new SL structure is unveiled for a sample consisting of thin GeTe and Sb2Te3 layers, which suggests intermixing of Ge atoms. This all-optical technique based on observation of coherent FLA modes offers a non-destructive characterization of superlattice structures at atomic resolution.
AB - Chalcogenide superlattices (SL) consist of alternately stacked GeTe and Sb2Te3 layers. The structure can act as a 3D topological insulator depending on the constituent layer thicknesses, making the design of the SL period a central issue for advancing chalcogenide SL as potential candidates for spin devices as well as for optimization of the current generation of phase-change memory devices. Here we explore the periodic structure of chalcogenide SL by observing coherent folded longitudinal acoustic (FLA) phonons excited by femtosecond laser pulse irradiation. The peak frequency of the FLA modes is observed to change upon variation of the thickness of the GeTe layer, which is well reproduced by means of an elastic continuum model. In addition, a new SL structure is unveiled for a sample consisting of thin GeTe and Sb2Te3 layers, which suggests intermixing of Ge atoms. This all-optical technique based on observation of coherent FLA modes offers a non-destructive characterization of superlattice structures at atomic resolution.
KW - acoustic phonons
KW - chalcogenide superlattices
KW - phase-change materials
KW - ultrafast spectroscopy
KW - zone-folding
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U2 - 10.1002/pssr.201800246
DO - 10.1002/pssr.201800246
M3 - Letter
AN - SCOPUS:85053006855
VL - 12
JO - Physica Status Solidi - Rapid Research Letters
JF - Physica Status Solidi - Rapid Research Letters
SN - 1862-6254
IS - 9
M1 - 1800246
ER -