2 research outputs found
Observation of Charge Transfer in Heterostructures Composed of MoSe<sub>2</sub> Quantum Dots and a Monolayer of MoS<sub>2</sub> or WSe<sub>2</sub>
Monolayer transition metal dichalcogenides
(TMDs) are atomically
thin semiconductor films that are ideal platforms for the study and
engineering of quantum heterostructures for optoelectronic applications.
We present a simple method for the fabrication of TMD heterostructures
containing MoSe<sub>2</sub> quantum dots (QDs) and a MoS<sub>2</sub> or WSe<sub>2</sub> monolayer. The strong modification of photoluminescence
and Raman spectra that includes the quenching of MoSe<sub>2</sub> QDs
and the varied spectral weights of trions for the MoS<sub>2</sub> and
WSe<sub>2</sub> monolayers were observed, suggesting the charge transfer
occurring in these TMD heterostructures. Such optically active heterostructures,
which can be conveniently fabricated by dispersing TMD QDs onto TMD
monolayers, are likely to have various nanophotonic applications because
of their versatile and controllable properties
Simple Chemical Treatment to n‑Dope Transition-Metal Dichalcogenides and Enhance the Optical and Electrical Characteristics
The
optical and electrical properties of monolayer transition-metal
dichalcogenides (1L-TMDs) are critically influenced by two dimensionally
confined exciton complexes. Although extensive studies on controlling
the optical properties of 1L-TMDs through external doping or defect
engineering have been carried out, the effects of excess charges,
defects, and the populations of exciton complexes on the light emission
of 1L-TMDs are not yet fully understood. Here, we present a simple
chemical treatment method for n-dope 1L-TMDs, which also enhances
their optical and electrical properties. We show that dipping 1Ls
of MoS<sub>2</sub>, WS<sub>2</sub>, and WSe<sub>2</sub>, whether exfoliated
or grown by chemical vapor deposition, into methanol for several hours
can increase the electron density and also can reduce the defects,
resulting in the enhancement of their photoluminescence, light absorption,
and the carrier mobility. This methanol treatment was effective for
both n- and p-type 1L-TMDs, suggesting that the surface restructuring
around structural defects by methanol is responsible for the enhancement
of optical and electrical characteristics. Our results have revealed
a simple process for external doping that can enhance both the optical
and electrical properties of 1L-TMDs and help us understand how the
exciton emission in 1L-TMDs can be modulated by chemical treatments