Dresden 2020 – scientific programme

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DS: Fachverband Dünne Schichten

DS 22: 2D semiconductors and van der Waals heterostructures V (joint session HL/DS/O)

DS 22.11: Talk

Wednesday, March 18, 2020, 12:30–12:45, POT 81

Decreasing Activation Energies with Thickness of Thin HfTe₅ layers — •Christopher Belke¹, Sonja Locmelis², Lars Thole¹, Peter Behrens², and Rolf J. Haug¹ — ¹Institut für Festkörperphysik, Leibniz Universität Hannover, 30167 Hannover, Germany — ²Institut für Anorganische Chemie, Leibniz Universität Hannover, 30167 Hannover, Germany

Hafnium pentatelluride (HfTe₅) is a layered two dimensional material from the class of Transition Metal Penta Chalcogenide with the chemical formula MX₅, where M is a transition metal and X a chalcogenide [1]. HfTe₅ shows a resistivity anomaly and is expected to be a topological insulator [2] with a bulk band gap of about 22 meV [3]. In addition, theory predicts that a single layer should show a band gap of about 400 meV and should be a quantum spin hall insulator [1].

We present that the electronic properties of HfTe₅ drastically change with decreasing thickness. We prepared samples with different thicknesses under 100 nm and made temperature dependent measurements to determine the activation energy in an Arrhenius plot. We found that the band gap increases with decreasing thickness. Conductivity measurements also show an anomaly due to a mobility change at around 120 K.

[1] H. Weng et al., Phys. Rev. X 4, 011002 (2014)

[2] S. Liu et al., APL Materials 6, 121111 (2018)

[3] H. Wang et al., Phys. Rev. B 93, 165127 (2016)