Regensburg 2022 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 30: Poster 2

HL 30.39: Poster

Donnerstag, 8. September 2022, 11:00–13:00, P3

Probing structural dynamics in optically excited 2D heterostructures by Ultrafast Electron Diffraction — •Mashood Tariq Mir, Arne Ungeheuer, Ahmed Hassanien, Lukas Nöding, Arne Senftleben, and Thomas Baumert — University of Kassel, 34132 Kassel, Germany

Layered transition metal dichalcogenides (TMDs) host a rich collection of physical properties, opening many different applications with atomically thin films such as sensors, electronic switching, or energy storage. Among those materials, 1T-TaS2 exhibits a complex phase diagram depending on temperature encompassing charge density waves (CDW) with diverse commensurabilities. New phenomena have been observed and are further expected from combining different materials to 2D heterojunctions. We aim to use femtosecond laser pulses to induce rapid structural changes and probe them with ultrafast electron diffraction (UED). In this work, free-standing single-crystalline heterostructure samples were prepared down to a few nanometre thicknesses to allow electron diffraction in transmission mode. The preparation method was optimized using atomic force microscopy and optical microscopy to isolate atomically thin flakes. In addition, we present an initial UED study of CDW heterostructure (1T-TaS2 / Graphite). Upon lattice heating, the CDW material undergoes several phase transitions. We focus on the reversible phase transition of 1T-TaS2 from the nearly commensurate to the incommensurate phase and study the effect of interlayer coupling of stacked 1T-TaS2 / Graphite heterostructures.