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
Thickness-Dependent Phonon Renormalization and Enhanced Raman Scattering in Ultrathin Silicon Nanomembranes
We
report on the thickness-dependent Raman spectroscopy of ultrathin
silicon (Si) nanomembranes (NMs), whose thicknesses range from 2 to
18 nm, using several excitation energies. We observe that the Raman
intensity depends on the thickness and the excitation energy due to
the combined effects of interference and resonance from the band-structure
modulation. Furthermore, confined acoustic phonon modes in the ultrathin
Si NMs were observed in ultralow-frequency Raman spectra, and strong
thickness dependence was observed near the quantum limit, which was
explained by calculations based on a photoelastic model. Our results
provide a reliable method with which to accurately determine the thickness
of Si NMs with thicknesses of less than a few nanometers