Περίληψη |
During the last decade, the interest in investigating two dimensional materials was
rapidly increased. Particularly, a class of materials known as Transition Metal
Dichalcogenides (TMDs) exhibit promising properties in their two-dimensional form,
making them attractive for future fundamental studies and applications. Some challenges
considering the isolation and identification of TMD monolayers have been dealt through
the introduction of a standard spectroscopic set of techniques such as Raman, Absorbance
and Photoluminescence. For the last couple of years many studies have been focused in the
examination of WS2/graphene heterostructures in order to explore their optoelectronic
properties.
The aim of this dissertation is two-fold. Firstly, the fabrication of the heterostructure
samples was carried out using mechanical exfoliation for isolating WS2 monolayers and
few-layer graphene flakes. The exfoliated flakes were subsequently identified and
characterized using optical microscopy and a combination of the three spectroscopic
techniques. Additionally, a deterministic transfer setup was used for the stamping
procedure in combination with the annealing treatment of samples. The importance of
annealing for the coupling of the layers was confirmed and highlighted throughout the
project. The second goal of this work was the spectroscopic study of the excitonic
properties of WS2/graphene heterostructures, which are strongly correlated with their
optoelectronic properties. Therefore, the optical response of the sandwiched sample was
examined under temperature dependent Photoluminescence in the range of 78K-300K.
|