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HL: Fachverband Halbleiterphysik

HL 74: Poster IIIA

HL 74.18: Poster

Donnerstag, 19. März 2020, 15:00–17:30, P2/2OG

Phase transition measurements of atomically thin 1T-TaS2 probed with ultrafast electron diffraction — •Mashood Tariq Mir, Arne Ungeheuer, Ahmed Hassanien, Arne Senftleben, and Thomas Baumert — Institute of Physics and CINSaT, University of Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany

The layered transition metal dichalcogenides (TMDs) host a rich collection of physical properties which may open 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. We aim to use femtosecond laser pulses to induce rapid structural changes and probe the following with ultrafast electron diffraction (UED). In this work, free-standing single-crystalline sample were prepared down to a few nanometer thicknesses to allow electron diffraction in transmission mode. The samples were mechanically exfoliated from different adhesive surfaces. 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 phases of 1T-TaS2. Upon lattice heating, the material undergoes several phase transitions. We are focusing on the reversible phase transition from the nearly commensurate to incommensurate phase in which the commensurate phase disappears, while the incommensurate phase emerges without causing irreversible damage to the underlying crystal.