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Your search keyword '"Mitrofanov, Kirill V."' showing total 21 results
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21 results on '"Mitrofanov, Kirill V."'

1. Sub-nanometre resolution of atomic motion during electronic excitation in phase-change materials

Author

Mitrofanov, Kirill V., Fons, Paul, Makino, Kotaro, Terashima, Ryo, Shimada, Toru, Kolobov, Alexander V., Tominaga, Junji, Bragaglia, Valeria, Giussani, Alessandro, Calarco, Raffaella, Riechert, Henning, Sato, Takahiro, Katayama, Tetsuo, Ogawa, Kanade, Togashi, Tadashi, Yabashi, Makina, Wall, Simon, Brewe, Dale, and Hase, Muneaki

Subjects
Condensed Matter - Materials Science
Abstract

Phase-change materials based on Ge-Sb-Te alloys are widely used in industrial applications such as nonvolatile memories, but reaction pathways for crystalline-to-amorphous phase-change on picosecond timescales remain unknown. Femtosecond laser excitation and an ultrashort x-ray probe is used to show the temporal separation of electronic and thermal effects in a long-lived ($>$100 ps) transient metastable state of Ge$_{2}$Sb$_{2}$Te$_{5}$ with muted interatomic interaction induced by a weakening of resonant bonding. Due to a specific electronic state, the lattice undergoes a reversible nondestructive modification over a nanoscale region, remaining cold for 4 ps. An independent time-resolved x-ray absorption fine structure experiment confirms the existence of an intermediate state with disordered bonds. This newly unveiled effect allows the utilization of non-thermal ultra-fast pathways enabling artificial manipulation of the switching process, ultimately leading to a redefined speed limit, and improved energy efficiency and reliability of phase-change memory technologies., Comment: 8 pages, 4 figures

Published
2017
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2. Picosecond strain dynamics in Ge$_{2}$Sb$_{2}$Te$_{5}$ monitored by time-resolved x-ray diffraction

Author

Fons, Paul, Rodenbach, Peter, Mitrofanov, Kirill V., Kolobov, Alexander V., Tominaga, Junji, Shayduk, Roman, Giussani, Alessandro, Calarco, Raffaella, Hanke, Michael, Riechert, Henning, Simpson, Robert E., and Hase, Muneaki

Subjects
Condensed Matter - Materials Science
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., Comment: 7 pages, 4 figures, Phys. Rev. B, in press

Published
2014
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7. Origin of resistivity contrast in interfacial phase-change memory: The crucial role of Ge/Sb intermixing

Author

Saito, Yuta, Kolobov, Alexander V, Fons, Paul, Mitrofanov, Kirill V, Makino, Kotaro, Tominaga, Junji, Robertson, John, and Apollo - University of Cambridge Repository

Subjects
5104 Condensed Matter Physics, 51 Physical Sciences
Abstract

Phase-change memories based on reversible amorphous-crystal transformations in pseudobinary GeTe-Sb2Te3 alloys are one of the most promising nonvolatile memory technologies. The recently proposed superlattice-based memory, or interfacial phase-change memory (iPCM), is characterized by significantly faster switching, lower energy consumption, and better endurance. The switching mechanism in iPCM, where both the SET and RESET states are crystalline, is still contentious. Here, using the ab initio density functional theory simulations, a conceptually new switching mechanism for iPCM is derived, which is based on the change in the potential landscape of the bandgap, associated with local deviations from the pseudobinary stoichiometry across the van der Waals gaps and the associated shift of the Fermi level. The crucial role in this process belongs to Ge/Sb intermixing on the cation planes of iPCM. These findings offer a comprehensive understanding of the switching mechanisms in iPCM and are an essential step forward to the insightful development of phase-change memory technology.

Published
2019

8. Chalcogenide Materials Engineering for Phase‐Change Memory and Future Electronics Applications: From Sb–Te to Bi–Te.

Author

Saito, Yuta, Mitrofanov, Kirill V., Makino, Kotaro, Fons, Paul, Kolobov, Alexander V., Tominaga, Junji, Uesugi, Fumihiko, and Takeguchi, Masaki

Subjects
*PHASE change materials, *BINARY metallic systems, *CHALCOGENIDES, *NONVOLATILE memory, *DENSITY functional theory, *BARIUM titanate, *PYROLYTIC graphite
Abstract

Chalcogenide materials play essential roles in modern nonvolatile memory technology in the form of both phase‐change memory (PCM) and selector devices. Herein, Bi–Te binary alloys are explored as an alternative candidate for superlattice (SL) or interfacial PCM (iPCM). GeTe/Bi4Te3 (GT/BT) SL exhibits similar structural features to conventional GeTe/Sb2Te3 (GT/ST) SL, such as highly oriented crystal grains and intermixing. Furthermore, preliminary device measurements show that Ge–Bi–Te (GBT) SL switches in a similar manner to conventional Ge–Sb–Te (GST), suggesting that they may be a promising candidate for memory applications. In addition, Bi2Te3/Sb2Te3 (BT/ST) heterostructure films have been successfully fabricated and show clear interface stacking at the atomic level. Although the BT/ST heterostructure is ostensibly a p–n junction, rectifying behavior is not observed in current (I)–voltage (V) measurements due to the existence of a large number of carriers in both layers. Finally, density functional theory (DFT)‐based simulations suggest that an ideal BT/ST heterostructure may possess intriguing topological properties that can enable novel functional devices. The Bi–Te binary alloys offer promising potential for optimizing PCM performance as well as for the realization of novel functional electronic devices. [ABSTRACT FROM AUTHOR]

Published
2021
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17. Sub-nanometre resolution of atomic motion during electronic excitation in phase-change materials

Author

Mitrofanov, Kirill V., primary, Fons, Paul, additional, Makino, Kotaro, additional, Terashima, Ryo, additional, Shimada, Toru, additional, Kolobov, Alexander V., additional, Tominaga, Junji, additional, Bragaglia, Valeria, additional, Giussani, Alessandro, additional, Calarco, Raffaella, additional, Riechert, Henning, additional, Sato, Takahiro, additional, Katayama, Tetsuo, additional, Ogawa, Kanade, additional, Togashi, Tadashi, additional, Yabashi, Makina, additional, Wall, Simon, additional, Brewe, Dale, additional, and Hase, Muneaki, additional

Published
2016
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18. Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

Author

Fons, Paul, primary, Rodenbach, Peter, additional, Mitrofanov, Kirill V., additional, Kolobov, Alexander V., additional, Tominaga, Junji, additional, Shayduk, Roman, additional, Giussani, Alessandro, additional, Calarco, Raffaella, additional, Hanke, Michael, additional, Riechert, Henning, additional, Simpson, Robert E., additional, and Hase, Muneaki, additional

Published
2014
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21. Picosecond strain dynamics in Ge2Sb2Te5 monitored by time-resolved x-ray diffraction.

Author

Fons, Paul, Rodenbach, Peter, Mitrofanov, Kirill V., Kolobov, Alexander V., Junji Tominaga, Shayduk, Roman, Giussani, Alessandro, Calarco, Raffaella, Hanke, Michael, Riechert, Henning, Simpson, Robert E., and Muneaki Hase

Subjects
*PICOSECOND pulses, *FEMTOSECOND pulses, *ULTRASHORT laser pulses, *PHASE transitions, *STATISTICAL thermodynamics
Abstract

Coherent phonons (CPs) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, nonthermal switching in phase-change materials such as Ge2Sb2Te5 (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 European Synchrotron Radiation Facility (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 excited-state effects 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. [ABSTRACT FROM AUTHOR]

Published
2014
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