Spectroscopic imaging ellipsometry of two-dimensional TMDC heterostructures

• Main Authors: Sigger, Florian, Lambers, Hendrik, Katharina, Nisi, Klein, Julian, Saigal, Nihit, Holleitner, Alexander W, Wurstbauer, Ursula
• Format: Journal Article
• Language: English
• Published: 11-07-2022
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.2207.04633

Semiconducting two-dimensional materials and their heterostructures gained a
lot of interest for applications as well as fundamental studies due to their
rich optical properties. Assembly in van der Waals heterostacks can
significantly alter the intrinsic optical properties as well as the
wavelength-dependent absorption and emission efficiencies making a direct
comparison of e.g. photoluminescence intensities difficult. Here, we determine
the dielectric function for the prototypical MoSe2/WSe2 heterobilayer and their
individual layers. Apart from a redshift of 18 meV - 44 meV of the
energetically lowest interband transitions, we find that for larger energies
the dielectric function can only be described by treating the van der Waals
heterobilayer as a new artificial homobilayer crystal rather than a stack of
individual layers. The determined dielectric functions are applied to calculate
the Michelson contrast of the individual layers and the bilayer in dependence
of the oxide thickness of often used Si/SiO2 substrates. Our results highlight
the need to consider the altered dielectric functions impacting the Michelson
interference in the interpretation of intensities in optical measurements such
as Raman scattering or photoluminescence.