Dresden 2017 – scientific programme
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DS: Fachverband Dünne Schichten
DS 27: 2D Materials beyond Graphene (jointly with O)
DS 27.6: Poster
Tuesday, March 21, 2017, 18:30–20:30, P2-EG
Structural dynamics of TMDC heterostructures studied by femtosecond electron diffraction — •Daniela Zahn, Thomas Vasileiadis, Lutz Waldecker, and Ralph Ernstorfer — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Vertical heterostructures of two-dimensional (2D) crystals offer intriguing new perspectives for the fabrication of novel nanodevices [1]. Especially for optoelectronic devices, it is important to understand their relaxation dynamics after optical excitation, which are governed by the interplay of electronic and phononic coupling across the interface and electron-phonon coupling in the individual materials. One experimental technique that can directly observe the structural response to photoexcitation is femtosecond electron diffraction [2]. The evolution of the atomic mean-square-displacement can be experimentally accessed by means of the Debye-Waller effect. Our focus lies on heterostructures with staggered (type II) band alignment, which exhibit photo-induced charge separation across the interface. We present results on bulk WSe2/WS2 heterostructures revealing sub-picosecond transfer of hot charge carriers across the interface and intralayer energy transfer from the charge carriers to the lattice on a timescale of few picoseconds in both materials. The results suggest that the equilibration between the two materials is carried out primarily by hot charge carrier transfer while vibrational coupling plays a minor role.
[1] A. Geim, I.V. Grigorieva, Nature 499, 419-425 (2013).
[2] L. Waldecker, R. Bertoni, R. Ernstorfer, JAP 117, 044903 (2015).