Sub‐Picosecond Non‐Equilibrium States in the Amorphous Phase of GeTe Phase‐Change Material Thin Films

• Published in: Advanced materials (Weinheim) Vol. 33; no. 41; pp. e2102721 - n/a
• Main Authors: Martinez, Paloma, Blanchet, Valérie, Descamps, Dominique, Dory, Jean‐Baptiste, Fourment, Claude, Papagiannouli, Irène, Petit, Stéphane, Raty, Jean‐Yves, Noé, Pierre, Gaudin, Jérôme
• Format: Journal Article Web Resource
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-10-2021; Wiley-VCH Verlag; Wiley-Blackwell
• Subjects: Amorphous materials; amorphous phase; chalcogenides; Chemical Physics; Dielectric properties; Distribution functions; Electron distribution; Equilibrium conditions; Excitation; fast transitions; Germanium; GeTe; Memory devices; Molecular dynamics; ovonic threshold switching; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; Surface dynamics; Tellurides; Thin films; chalcogenide; amorphous; fast transition; GeTe; ovonic threshold switching
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202102721

The sub‐picosecond response of amorphous germanium telluride thin film to a femtosecond laser excitation is investigated using frequency‐domain interferometry and ab initio molecular dynamics. The time‐resolved measurement of the surface dynamics reveals a shrinkage of the film with a dielectric properties’ response faster than 300 fs. The systematic ab initio molecular dynamics simulations in non‐equilibrium conditions allow the atomic configurations to be retrieved for ionic temperature from 300 to 1100 K and width of the electron distribution from 0.001 to 1.0 eV. Local order of the structures is characterized by in‐depth analysis of the angle distribution, phonon modes, and pair distribution function, which evidence a transition toward a new amorphous electronic excited state close in bonding/structure to the liquid state. The results shed a new light on the optically highly excited states in chalcogenide materials involved in both important processes: phase‐change materials in memory devices and ovonic threshold switching phenomenon induced by a static field.
The sub‐picosecond response of amorphous GeTe thin film to femtosecond laser excitation is investigated using frequency‐domain interferometry and ab initio molecular dynamics. The results shed a new light on the optically highly excited states in chalcogenide materials involved in both important processes: phase‐change materials in memory devices and ovonic threshold switching phenomenon induced by a static field.