Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 91: Poster IIIb (Joint session of DS and HL, organized by HL)

HL 91.13: Poster

Donnerstag, 10. März 2016, 16:00–19:00, Poster A

The substrate dependence of localizing excitons in WSe2 monolayers — •Jhih-Sian Tu¹, Sven Borghardt¹, Florian Winkler², Detlev Grutzmacher¹, and Beata Kardynal¹ — ¹PGI-9, Forschungszentrum Juelich, Juelich, Germany — ²ER-C, Forschungszentrum Juelich, Juelich, Germany

Monolayer transition-metal dichalcogenides (TMDs) have become new building blocks for two-dimensional (2D) heterestructures which are composed of monolayers of different materials bound with Van der Waals forces. In this study, the photoluminescence (PL) of WSe2 monolayers (ML) is compared with that of hexagonal-boron nitride (hBN)/WSe2 ML/hBN heterostructures. The samples were prepared by PDMS dry transfer of WSe2 MLs on target substrates (SiO2 or hBN). The PL measurements showed that encapsulation leads to a suppression of the free exciton emission and to a shift of the exciton emission energy. An impurity band emission, although present in all sample geometries, is also strongly modified by the encapsulation. It is present across the whole sample and takes a form of a set of sharp emission lines in wide wavelength range. These sharp emission lines are linearly polarized as in the case of the emission from the localized states in WSe2 on SiO2 or on hBN. Variations in geometries of measured samples allow the analysis of the data in terms of influence of external impurities, intrinsic defects and a surface strain caused by hBN encapsulation. We discuss the substrate choice for the control of photoluminescence from localized states in WSe2 ML.