Two-dimensional materials hold a great promise for developing extremely fast, compact and inexpensive optoelectronic devices. A molybdenum disulphide (MoS 2) monolayer is an important example which shows strong, stable and gate tunable optical response even at room temperature near excitonic transitions. However, optical properties of a MoS 2 monolayer are not documented well. Here, we investigate the electric field effect on optical properties of a MoS 2 monolayer and extract the dependence of MoS 2 optical constants on gating voltage. The field effect is utilised to achieve~10% visible light modulation for a hybrid electro-optical waveguide modulator based on MoS 2. A suggested hybrid nanostructure consists of a CMOS compatible Si 3 N 4 dielectric waveguide sandwiched between a thin gold film and a MoS 2 monolayer which enables a selective enhancement of polarised electroabsorption in a narrow window of angles of incidence and a narrow wavelength range near MoS 2 exciton binding energies. The possibility to modulate visible light with 2D materials and the robust nature of light modulation by MoS 2 could be useful for creation of reliable ultra-compact electro-optical hybrid visible-light modulators.

Metal-dielectric-graphene hybrid heterostructures based on oxides Al2O3, HfO2, and ZrO2 as well as on complementary metal–oxide–semiconductor compatible dielectric Si3N4 covering plasmonic metals Cu and Ag have been fabricated and studied. We show that the characteristics of these heterostructures are important for surface plasmon resonance biosensing (such as minimum reflectivity, sharp phase changes, resonance full width at half minimum and resonance sensitivity to refractive index unit (RIU) changes) can be significantly improved by adding dielectric/graphene layers. We demonstrate maximum plasmon resonance spectral sensitivity of more than 30,000 nm/RIU for Cu/Al2O3 (ZrO2, Si3N4), Ag/Si3N4 bilayers and Cu/dielectric/graphene three-layers for near-infrared wavelengths. The sensitivities of the fabricated heterostructures were ~ 5–8 times higher than those of bare Cu or Ag thin films. We also found that the width of the plasmon resonance reflectivity curves can be reduced by adding dielectric/graphene layers. An unexpected blueshift of the plasmon resonance spectral position was observed after covering noble metals with high-index dielectric/graphene heterostructures. We suggest that the observed blueshift and a large enhancement of surface plasmon resonance sensitivity in metal-dielectric-graphene hybrid heterostructures are produced by stationary surface dipoles which generate a strong electric field concentrated at the very thin top dielectric/graphene layer.

In lanthanide-sensitized upconversion (UC) nanomaterials, the typical sensitizer Yb3+ can significantly modulate the codoped activator (such as Er3+ ions) to generate multiband transitions. However, the kinetics of these multiband emissions...

One of the exciting features of graphene is a possibility to affect its electrical, optical, and chemical properties by gating, that is, by application of an electric field. This requires reasonably large fields (at the level of 1 V/nm necessary to induce relevant electron density changes) applied over a gating dielectric material. At these fields, most dielectrics show some conduction, which leads to an important question: what is the best dielectric to gate graphene? Here, we show that this question is imprecise as a dielectric material produced by different fabrication methods can exhibit dramatically different gating properties. Namely, we show that two oxide dielectrics (hafnia and alumina) result in positive hysteresis of graphene gating characteristics being fabricated by atomic layer deposition and negative hysteresis being fabricated by electron beam evaporation. We attribute this behavior to the stoichiometry of the samples and oxygen ion migration. It implies that oxide dielectrics should be avoided in graphene gated devices working at room temperatures.

No abstract