A hybrid emitter - metal nanoplasmonic platform – HYBNAP
The optical properties of emitting nanoparticles such as quantum dots (QD) or NV centers in nanodiamonds (ND) have been extensively studied in solution or in vivo, isolated on dielectric or plasmonic substrates, coupled to metallic colloids or even attached to near-field scanning probes. Yet, optical studies have been performed with macroscopic or diffraction limited techniques. One noticeable exception is the cathodoluminescence (CL) study of isolated QD in the 1990s and recently of isolated nanodiamonds.
The HYBNAP project proposes to study hybrid structures made by coupling gold nanoparticles with well-defined plasmonic modal properties to emitting nanoparticles with 1-nm probes of electron energy-loss spectroscopy (EELS), CL and photon scanning tunneling microscopy (PSTM) to locally excite and characterize their optical response. The project dedicates particular attention to build the hybrid emitter-metal structure with nanometer controlled geometries by combining colloidal synthesis and self-assembly with advanced templating effects of sub-10 nm patterned substrates structures. Theoretical modelling and numerical simulations is implemented to interpret the experimental data. In order to carry out this widely interdisciplinary research program and reach an unprecedented spatial precision combined with spectral insight, a flexible research platform is created for investigating and tuning nano-optical properties of hybrid emitter / metal nanoplasmonic systems. The work is realized by the joint force of a strong team that combines expertise in colloidal chemistry and self-assembly (CEMES Toulouse & SCR Rennes, Fr), ultimate nanofabrication (SUTD Singapore), nanoplasmonics modelling and simulations (IHPC Singapore & CEMES) and nano-optical characterization (IMRE Singapore & CEMES).
The HybNaP partners first focus on acquiring, with nanometer precision, the mapping of surface plasmon (SP) modal distributions in a series of nanoparticles, 1D and 2D crystalline structures produced by CEMES and SCR by using TEM-based electron beams at IMRE. The results are benchmarked to linear and non-linear optical imaging that have been recently shown to probe the partial SP local density of states (LDOS) and confronted to theoretical models associated to numerical simulation tools based on finite element or 3D-Green Dyadic methods. Preliminary work has by IMRE and CEMES has led to a 2015 publication in Nature Mater. IMRE is one of the very few places worldwide where combined EELS / CL measurements are possible. CL is recorded to allow correlating local excitation and photon emission. In parallel, low energy electron excitation with similarly spatial confinement is developed at CEMES by recording luminescence under STM tip excitation. Data interpretation will be supported by STEM measurements and IHPC's modeling of SP emission spectra from a tunnel junction.
Meanwhile, metal-emitter hybrid structures composed of gold colloids and QD or ND will be synthesized by CEMES and SCR and coupled by using molecular coupling approaches. Protocols to restrict the assembly to dimers and small oligomers are targeted. Alternatively, a colloidal epitaxy approach in which quantum nanorods are used as templates to grow metallic nanoparticles at the tips is explored. Hybrid structures of increasing complexity are obtained by doping plasmonic nanoparticle networks with QD or ND.
Finally, hybrid plasmon-emitter with improved topology will be produced by combining colloidal chemistry with high resolution electron-beam lithography. Mix & matching will allow to tune the relative location of the emitter and the nodes of the SP modal distribution and to place it where the SP-LDOS is intense. Structures will be made that can be measured both in the near- and far-field. Simulation routines guide the design of efficient hybrid structures able to excite dark plasmon modes that are otherwise inaccessible, leading to hybrid materials with unique, tunable optical properties.
Monsieur Erik DUJARDIN (CNRS DR MIDI-PYRENEES)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IHPC Institute of High Performance Computing
CEMES UPR8011 CNRS DR MIDI-PYRENEES
IMRE the Institute of Materials Research and Egineering
SCR UMR6226 Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS
SUTD Singapore University of Technology and Design
Help of the ANR 270,000 euros
Beginning and duration of the scientific project: October 2016 - 36 Months