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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - Phonsi (Nanophotonics by Nanocrystals, from integration to single photon operation)

Teaser

Summary

Optical nanomaterials - in which components are smaller than 100 nm - are driving an anticipated huge impact to make our future way of living sustainable and comfortable. For example:
* Optical fibre networks underlie the data communications that are vital for our on-line activities. Photonic devices run on light, and innovations in such devices can combine lower power consumption with higher speed operation. One mechanism for this is incorporating optically active materials such as quantum dots or graphene for emitting, detecting and modulating light.
* Infrared spectroscopic systems are widely used for chemical analysis. The use of these systems can find further application if they can be ported to a low-cost, consumer optical platform. One such means is by integrating the spectroscopic functionality along with low-cost ultra-high sensitivity quantum dot or graphene photodetectors on an integrated circuit.
* Solid-state lighting allows for power-efficient lighting and display applications. Generating the desired colors for solid state lighting requires luminescent materials with special characteristics. Core/shell quantum dots are novel materials that can meet these needs in an affordable manner.

Next-generation photonic devices rely heavily on a hybrid approach of photonics and nanomaterials technology. This is a vibrant, worldwide field of research and development where scientific discoveries are quickly brought to the market by established companies or newly-founded spin-off companies. For Europe to benefit from the results, it must invest in appropriate training of future researchers. The Phonsi network is our response for training needs. This approach brings together universities, research institutes and companies in a multidisciplinary research and training network covering the chemical synthesis of nanomaterials, top-down and bottom-up nanomaterials processing, the analysis of light-matter interaction and charge-carrier transport and the simulation, formation and testing of nanophotonic devices. The participating researchers are trained in a unique environment that offers them all the skills needed to pursue their careers in relevant European industrial activities.

The Phonsi research programme has four main objectives:
1. Synthesis of quantum dots for nanophotonics-by-nanocrystal devices.
2. Development of a hybrid top-down/bottom-up processing technology.
3. A deep understanding and tuning of the properties of excitons in quantum dots relevant to the intended devices.
4. Formation of nanophotonics-by-nanocrystal devices that combine progress at the materials level with optimized device design.
To achieve these objectives, phonsi has engaged leading academic and non-academic partners with complementary world-class backgrounds.

Work performed

Objective 1: Smart Nanocrystals for Nanophotonics

InP/ZnE (E=S,Se) synthesis
InP precursor chemistry
Cu-doped InP quantum dots
Multiple â€˜flashâ€™ CdSe/CdS/ZnS QDs
PbS/CdS QDs by additive shell growth
HgSe/CdS(e) QDs by additive shell growth
InAs Colloidal Quantum Dots Synthesis via Aminopnictogen Precursor Chemistry
Innovative InP-based core/shell quantum dots
Formation and characterization of blue, green, red and white light emitting supraparticles, and supra-particle lasers
Development of Cd-free luminescent nanocrystals for integration in Si- and SiC opto-electronics
Fabrication of 2-D semiconductors with a superimposed nanogeometry, resulting in novel band structure and opto-electronics

Objective 2: Hybrid top-down/botton-up processing
Surface chemistry of CsPbBr3 nanocrystals
Ligand addition energy and nanocrystal stoichiometry
Nanoscale and Single-Dot Patterning of Colloidal Quantum Dots
Surface chemistry of InP-based core/shell quantum dots
Thermodynamics of ligand displacement reactions
Chemically triggered PbSe superlattice formation
Embedding of colloidal quantum dots by atomic layer deposition
Optical properties of HgSe quantum dots
Optical amplification by HgTe quantum dots
Single-exciton optical gain in semiconductor nanocrystals: Positive role of electron-phonon coupling
Sub-micron sized single Gaussian defect cavity on a mesa structure

Objective 3: Excitons and Charge Carriers in QDs and QD Nanocomposites
Single QDs
Magneto-optical properties of bulk and QDs Cs-based Perosvkites
Magnetically doped colloidal QDs
Synthesis and characterization of layered semiconductors of MPS3
Assemble QDs
Single QDs
Ink-jet printed phototransistors

Objective 4: Nanophotonics-by-nanocrystals devices
CdSe nanoplatelets
Superconducting nanowire single photon detectors
Integrated nanophotonics-by-nanocrystals photodetectors
Hybrid QD-SiN waveguide platform
Enhancement of single-photon emission and polarization dependent coupling in SiNx waveguides
QDs in suspended SiNx waveguides
Electrically injected single photon emitter
Hybrid QD-SiN waveguide platform

All the above mentioned objectives were achieved during the course of the project.

Final results

Colloidal QDs offer a potential combination second to none of tunable materials properties and a suitability for solution-based processing. The underlying challenge is to turn QDs into a mature material platform and realize their full potential for nanophotonic devices. It requires QDs with the right properties, a processing technology to combine QDs with integrated photonics platforms and simulation and characterization of devices, all in the context of an emerging field that actively transfers scientific findings to the market.

A number of recent breakthroughs have made QDs ready to become an active optical material in even the most advanced nanophotonics devices. We demonstrated the formation of nanoplatelets with emission linewidths as narrow as 5-10 nm. We also found that blinking in the emission of single QDs could be eliminated by growing thick, alloyed shells, and also showed how wavefunction engineering by shell growth reduces exciton relaxation and dephasing in QDs. In addition, we recently discovered that nearly thresholdless, long lived optical amplification is possible when QDs are turned into effective 3-level systems.

Phonsi aims at building on these findings to synthesize QDs that exhibit non-blinking, highly efficient single photon emission or nearly thresholdless gain over a much broader wavelength range then currently demonstrated in the literature with a focus on heavy metal free materials. This brings phonsi at the forefront of developments in QD synthesis and it will make possible applications of QDs in integrated nanolasers and single photon sources.

Importantly, phonsi is not an isolated programme. Its focus on nanomaterials, solution-based processing and integration in nanophotonics devices is closely linked to various running research initiatives. Phonsi uniquely brings together research from different viewpoints, ranging from fundamental science to the business perspective, different domains, from chemistry to physics to engineering, and different methodologies, from material synthesis to analysis of properties and devices to simulation and modeling in a single project supported by some of the most outstanding researchers in the field. This offers a fertile, supradisciplinary training environment at the cross-roads of nanomaterials and nanophotonics for maximum impact.