BSc / MSc / internship projects: Studying Exciton Dynamics of Two-Dimensional Transition Metal Dichalcogenides

Please note: unless otherwise specified, the internships are only available for students with a nationality of an EU-member state and/or students from a Dutch university.

DIFFER (Dutch Institute for Fundamental Energy Research) is one of the NWO institutes and focuses on a multidisciplinary approach of the energy research combining physics, chemistry and materials engineering. The institute is an important part of the energy research strategy of NWO and FOM. The DIFFER mission is to carry out leading fundamental research in the field of fusion-energy and solar fuels, in close collaboration with academic institutions, research institutes and industry.

The group Photonics for Energy (PfE) investigates resonant light-matter interaction from the optical to the far-infrared at subwavelength and ultrashort spatial and time scales, with the goal of understanding fundamental phenomena that can be applied in energy research.

BSc / MSc / internship projects: Studying Exciton Dynamics of Two-Dimensional Transition Metal Dichalcogenides

Two dimensional (2D) materials such as graphene, black phosphorous, and transition metal dichalcogenides (TMDs) exhibit fascinating physical properties due to their specific band structure and reduced dimensionality. In recent years, TMDs (MX2, where M = Mo, W and X = S, Se) particularly are of much interest from a fundamental point of view but they also provide an excellent platform for ultrathin optoelectronic and photonic devices.

Similar to graphene, monolayer TMDs are composed of a 2D honeycomb lattice. As the material thickness is reduced to a single monolayer, TMDs transition from an indirect to a direct bandgap semiconductor, resulting in a thousand-fold increase in emission quantum efficiency at visible to near infrared wavelengths. Electron-hole pairs form tightly bound excitons with a ~ 1 nm Bohr radius and a > 300 meV binding energy, which are extremely stable at room temperature compared to traditional semiconductors.

The properties and characteristics of  monolayer TMDs provide us an elegant tool to study light-matter interaction at nanoscale. Combing 2D TMDs with nanophotonic structures (for example, plasmonic hole arrays as in Figure 1 or nanoparticle arrays), we investigate the fundamental properties of light emitters. In this project, we will concentrate on studying the exciton dynamics of 2D TMDs strongly coupled to nanophotonic structures, including the emission quantum yield, the photoluminescence lifetime and the photoconductivity of  both non-passivated and passivated TMDs.

If you are interested, please contact Dr. Shaojun Wang (s [368] wang [28] differ [368] nl), or Prof. Jaime Gomez Rivas (j [368] gomezrivas [28] differ [368] nl).

Figure 1.  An exfoliated WS2 monolayer deposited on a plasmonic hole array (left: white light microscope image, right: fluorescence image)