Financed scholarships:

• Reshaping the future: perovskites and chalcohalides semiconductor nanocrystals
• Tailoring conductive paths in novel plasmonic/electronic devices
• 2D transition metal dichalcogenides: CVD synthesis, electrical and optical characterization
• Coherent control of quantum materials
• Achieving quantum coherence in organic solar cells

Reshaping the future: perovskites and chalcohalides semiconductor nanocrystals

Student: Irina Guschina

Background and motivation

The demand for sustainable energy sources has driven extensive research efforts in various directions, unfolding a new era for emerging semiconductor materials. Over the past few decades, semiconductor materials have undergone thorough investigation for their potential applications in diverse devices, starting with solar cells and ending up with TVs. However, before these materials can be commercialized, scientists must address the challenges they encounter.

This thesis focuses on novel materials synthesis and characterization, as well as discussing potential applications and strategies for mitigating intrinsic and extrinsic instabilities in semiconductor materials. Specifically, it addresses:
1) Perovskite colloidal nanocrystals which show promise for solar cell and photodetector applications but exhibit instability under sunlight. Proposed solutions include methods to prevent anion segregation.
2) Exploration of a new class of materials known as chalcohalides, where novel materials have been synthesized and characterized for potential application in light-harvesting systems.
By touching these areas, the thesis aims to contribute to the advancement of sustainable energy technologies by providing insights characterization, and application of semiconductor materials.

Supervisors

Prof. Masaru Kuno, Notre Dame University, USA, mkuno@nd.edu
Dr. Liberato Manna, IIT, liberato.manna@iit.it
Prof. Luca Gavioli, Università Cattolica del Sacro Cuore, Italy, luca.gavioli@unicatt.it
Prof. Alexander Mukasyan, Notre Dame University, USA, amoukasi@nd.edu

Tailoring conductive paths in novel plasmonic/electronic devices

Student: Vincenzo Balzano (UCSC fellowship)

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Background and motivation

The frontier of electronics is the construction of neuromorphic circuits, i.e. a neural hardware mimicking the procedure used by human brains to process data. The main features of neuromorphic hardware should be: parallel multichannel operations, signal processing via comparison of input data with a specific activation functions and memorization of information until an erasing signal is applied. Substitution Traditional electronics to provide a faster data transfer and processing has been sometime provided by photonics. However, hybrid technologies, as for example plasmonic circuits, might represent a crossover point exploiting the advantages that each solution offers. In this context, the switching can be obtained by varying the absorption and scattering loss of a plasmonic mode within a specific insulator layer. Hence the material composing the layer play a fundamental role in determining the behavior of the optoelectronic device, in particular by controlling the conductivity and the switching performances. The present PhD program will investigate plasmonic devices (based on the propagation of Surface Plasmon Polariton quasiparticles) that might be applied as neuromorphic circuits. More specifically, the program will investigate novel materials and geometries to realize plasmonic memristors (re-writable memories based on resistive properties). The novel plasmonic memristors will be the basic elements to realize hybrid optic and electronic neuromorphic circuits. 
The project requires a student who focuses his activity on the design, construction and characterization of innovative multilayer plasmonic circuits. This will involve simulations of light propagation in nonlinear regime and of plasmonic propagation using both finite difference calculation codes and in COMSOL language. Moreover, the student will synthesize and characterize thin film and nanogranular materials for realization of the novel prototypes, which will be tested in the laboratory.

Supervisors

Prof. Luca Gavioli, Università Cattolica del Sacro Cuore (Italy), luca.gavioli@unicatt.it
Prof. Eugenio Fazio, Università La Sapienza (Italy), eugenio.fazio@uniroma1.it
Prof. Christopher L. Hinkle, University of Notre Dame (USA), chinkle@nd.edu

2D transition metal dichalcogenides: CVD synthesis, electrical and optical characterization

Student: Tummala Pinaka Pani (fellowship supported by CNR)

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Background and motivation

2D transition metal dichalcogenides (TMDs) hold great potential for application in different fields, in particular in nanoelectronics and photonics. In nanoelectronics, large energy dissipation due to heating in chips is unsustainable in terms of both costs and performance drop and 2D TMDs hold great potential to alleviate these problems. In photonics, the integration of 2D TMDs is predicted to enhance the energy harvesting. Towards such applications, it is crucial to develop a controlled, engineered, synthesis at large scale of such materials with high uniformity and to investigate their electronic/optical/thermal dynamics. Among the TMDs, MoS2 and MoTe2 are the most attractive materials to be investigated.
In this context our research project targets 2 main goals and some key aspects as follows:

1. Establish standard growth protocols for the chemical vapor deposition (CVD) synthesis of 2D TMDs at large scale on bulk flat and ad-hoc patterned substrates (i.e. SiO2/Si, Si3N4/Si).
   1.1 develop a scheme of a fabrication compatible with a process transferrable to the wafer scale;
   1.2 study the electrical and optical response of such structures in proto-devices (internal photoemission, electron transport, absorbance, photoluminescence, photoconductivity);
   1.3 explore transfer methods as key enabling technology for TMD integration to Si CMOS platform.
2. Develop time-resolved high resolution optical microscopy methods to investigate the electronic and thermo-mechanical aspects of 2D TMDs deposited on a bulk substrate.
   2.1 fast optical surface mapping in various environments (i.e. air and liquids) by microsphere assisted optical microscopy to get sensitivity to the few atomic layers constituting the surface termination;
   2.2 thermo-mechanical characteristics of the film-substrate adhesion and its uniformity (by optical techniques and dynamic AFM);
   2.3 investigation of the electronic and thermo-mechanical response of patterned surfaces.

Supervisors

Prof. Gabriele Ferrini, UCSC gabriele.ferrini@unicatt.it
Dr. Alessio Lamperti, IMM-CNR alessio.lamperti@mdm.imm.cnr.it
Prof. Valeri Afanasiev, KU-Leuven valeri.afanasiev@keuleuven.be
Prof. Christ Glorieux, KU Leuven christ.glorieux@kuleuven.be

Coherent control of quantum materials 

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Student: Matteo Zendra (fellowship co-financed on PRIN)
Student: Alessandra Milloch (UCSC fellowship)

Background and motivation

Controlling electronic quantum coherence in solids at ambient conditions is a long sought-after target in condensed matter physics. Quantum pathways could be exploited to coherently convert photons into charge excitations, to manipulate electronic phase transitions for quantum and neuromorphic computing, to control and store quantum information. Unfortunately, the quantum-coherent nature of electronic excitations in materials is usually lost on extremely fast timescales (few femtoseconds), as a consequence of the interactions with the incoherent fluctuations of the environment.  
The ultimate goal of this project is to investigate strategies to achieve the coherent optical control of the macroscopic properties of technologically relevant quantum materials. 
More specifically, the project will develop along the following lines:

• As a first step, we will develop an ultrafast experiment, based on the combination of a suitable number of phase coherent ultrashort optical pulses, to selectively excite solids. Particular effort will be dedicated to synthesize light pulses as short as 10 femtoseconds, via a non-collinear optical parametric amplifier (collaboration with Prof. Giulio Cerullo, Politecnico di Milano). In parallel, we will develop suitable theoretical modeling to treat quantum dynamics on ultrafast timescales and in interacting environments.
• As a second step, we will investigate the electronic decoherence dynamics in various correlated materials, such as LaVO3 and V2O3, which represent paradigmatic examples of correlation-driven Mott insulators. By combining the experimental and theoretical outcomes, we will address the possibility of enhancing the decoherence time by tuning the temperature, strain, excitation protocols and chemistry of the systems. We will also investigate the possibility of coherently manipulate the photoinduced insulator-to-metal transition in V2O3 and, possibly, to coherently control phase transition in other systems (e.g. superconductivity in copper oxides). 

Within the present project, two positions (1 mainly experimental and 1 mainly theoretical) are available. While on the experimental side the candidate is expected to acquire, during his/her PhD studies, the knowledge in the field of ultrafast and material science necessary to successfully fulfill the main goals, from the theoretical side her/his study will be focused on the development of mathematical many-body models for describing the coherent dynamics of correlated materials and on their analytical/numerical solving procedure. Depending on the expertise of the applicants, possible combinations of the theoretical and experimental tasks can be considered.
The candidate will join the joint activities of internationally recognized experimental groups in the field of ultrafast spectroscopies (experiments, UCSC), open quantum (theory, UCSC and KULeuven), oxide synthesis (experiments, KULeuven) and will interact with external theoretical (e.g. Prof. M. Capone SISSA Trieste; Hubbard model, DFT)  and experimental groups (e.g. Prof. G. Cerullo Politecnico di Milano; ultrafast experiments) collaborating to this project.

Supervisors

Prof. Claudio Giannetti, Università Cattolica del Sacro Cuore, Italy claudio.giannetti@unicatt.it
Prof. Fausto Borgonovi, Università Cattolica del Sacro Cuore, Italy fausto.borgonovi@unicatt.it
Prof. Jean Pierre Locquet, KULeuven, Belgium jeanpierre.locquet@fys.kuleuven.be
Prof. Wojciech De Roeck, KULeuven, Belgium wojciech.deroeck@kuleuven.be
Dr. Luca Celardo, Università di Firenze, Italy, giuseppeluca.celardo@unifi.it

Achieving quantum coherence in organic solar cells 

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Student: Gosetti Valentina (UCSC fellowship)

Background and motivation

Access to and control of the quantum-coherence of a system is emerging as a promising strategy for the realization of devices with disruptive properties and unprecedented efficiency. For instance, quantum coherence, in organic photovoltaics, could play a crucial role at each step of the photoconversion process. At the excitation stage (1), coherence (superposition) of excitonic states is proposed to amplify processes of multiexciton generation. During the exciton transport (2), energy losses can be minimized if the exciton diffuses on a distance comparable with its coherence (delocalization) length. Finally, if the charge collection (3) occurs on timescales faster than the electronic decoherence, the charge thermalization is ideally circumvented and the conversion efficiency maximized. 
Recently, coherent two-dimensional (2D) optical spectroscopy has been proposed for the measuring of the coherent and dephasing times. However, the interpretation of the spectra typically relies on theoretical modeling that can be highly nontrivial for complex systems. One more versatile solution is offered by interferometric time-resolved multi-photon photoelectron spectroscopy (inter-tr-mPPE). The technique exploits two phase-locked, delayed laser pulses generated in a Mach Zehnder interferometer to record one photoemission spectrum per time delay between two phase-coherent pulses. 
The aim of the present project is the realization of an inter-tr-2PPE setup to directly address coherences of an optical excitation and its dephasing in the time and energy domain. To achieve this, we are looking for a highly motivated student to implement the tr-2PPE spectroscopy facility available at the Elphos lab of the Department of Mathematics and Physics (Università Cattolica del Sacro Cuore) with a fully collinear interferometric scheme designed for inter-tr-mPPE experiments. This spectroscopy will be applied, for the first time, to organic systems, based on carbon nanostructures, grown and characterized in KU Leuven laboratories, combined with acene organic molecules where coherence is expected to act both at the excitation time and during the excitation transport on experimentally accessible and technologically promising timescales.

Supervisors

Prof. Stefania Pagliara, Università Cattolica del Sacro Cuore (Italy), stefania.pagliara@unicatt.it
Prof. Jin Won Seo, KU Leuven (Belgium), maria.seo@kuleuven.be