Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 17: Two-dimensional Materials I (joint session HL/CPP)

HL 17.13: Talk

Tuesday, April 2, 2019, 12:45–13:00, H36

Creation and optical spectroscopy of localized excitons in 2D MoS₂ — •Oleg Gridenco, Sven Mehrkens, Kathrin Sebald, Christian Tessarek, Martin Eickhoff, and Jürgen Gutowski — Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany

It is known that missing atoms in a semiconductor are exciton trapping sites, moreover, excitons can bind to impurity atoms or can be trapped in a potential well created by local strain or structural defects. In this context, structuring with a focused ion beam gives the opportunity for manipulation of 2D materials on the nanometer scale. In this study, we explore how focused gallium ion irradiation affects the intrinsic luminescence and vibrational properties of atomically thin MoS₂. Defects were introduced by scanning the Ga⁺ ion probe over a certain area of the flake using a focused ion beam (FIB). The amount of defects was controlled by varying the Ga⁺ ion dose starting from 2 x 10¹² ions/cm² until the PL signal was completely vanished (2 x 10¹³ ions/cm²). After Ga⁺ ion irradiation, micro-photoluminescence measurements at T=4K show that the A exciton emission is suppressed and a new peak, a bound exciton (D) located at 1.75 eV, emerges. This broad peak is redshifted by ΔE∼170 meV with respect to the neutral exciton X emission. Encapsulating monolayer MoS₂ into hBN drastically reduces the inhomogeneous contributions to the exciton linewidth [1]. The possibilities of tailoring optically active defect centers in 2D MoS₂ to even host single-photon emitters will be discussed.

[1] E. Courtade et al., Appl. Phys. Lett. 113, 032106 (2018).