Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 7: "New" Materials and New Physics in "Old" Materials I

HL 7.6: Vortrag

Montag, 26. März 2012, 10:45–11:00, EW 015

Low-temperature photocarrier dynamics in single-layer MoS₂ — •Tobias Korn, Gerd Plechinger, Stefanie Heydrich, Johannes Schmutzler, Michael Hirmer, and Christian Schüller — Institut für Experimentelle und Angewandte Physik, Universität Regensburg

The dichalcogenide MoS₂, which is an indirect-gap semiconductor in its bulk form, was recently shown to become an efficient emitter of photoluminescence as it is thinned to a single layer [1], indicating a transition to a direct-gap semiconductor due to confinement effects. Here, we present scanning Raman and time-resolved photoluminescence studies of few- and single-layer MoS₂ flakes [2]. Scanning Raman spectroscopy reveals the intensity and spectral position of the characteristic Raman vibration modes of the flake. Photoluminescence (PL) measurements are performed on single-layer areas of a flake. We clearly see two PL peaks at low temperatures, which we may assign to bound and free exciton transitions. Time-resolved PL traces reveal photocarrier recombination on the few-picosecond timescale at low temperatures. For temperatures above 150 K, we observe a longer-lived component of the PL, which we attribute to increased carrier-phonon interaction at higher temperatures.

[1] K. F. Mak et al., Phys. Rev. Lett. 105,136805 (2010).

[2] T. Korn et al., Appl. Phys. Lett. 99, 102109 (2011).