The research activity is mainly focused on two main topics: (i) the characterization of structural, compositional and functional properties of nanostructures and nanomaterials, in particular with electron microscopy (SEM, TEM, STEM) techniques; (ii) the comparison between the modeling of the properties of carbon nanostructures and the ones determined experimentally by means of advanced TEM techniques, like electron holography and Geometric Phase Analysis.
More in detail, the application of electron microscopy based techniques has been focused on:
• single and multi-layer graphene membranes synthesized by CVD
• chemically exfoliated graphene and graphene-oxide membranes
• mechanical properties of graphene membranes
• 3D graphene-based porous structures
• graphene-based nanocomposites materials (polymeric compounds, biological nanocomposites …)
• 2D materials beyond graphene (transition metal dichalcogenide like MoS2 and WS2, silicene, …)
• metal organic frameworks (MOF) and covalent organic frameworks (COF) integrated with graphene membranes
• fabricated and functionalized nanoparticles and quantum dots for energy and catalytic applications (Si nanocrystals, Pt nanoparticles, AuFe supported nanosystems)
• core-shell quantum dots with tailored optical properties (PbS/CdS with dual emission)
• semiconducting nanorods and nanowires in particular integrated in dielectric matrices and exfoliated graphene membranes (ZnO, TiO2 …)
• nanomaterials for cultural heritage preservation
• organic materials for organic electronics applications
In addition, the research activity is focused on the development of tailored and innovative detection techniques and devices. An innovative detector for transmitted electrons has been developed in collaboration with ZEISS in the last years, and a system for transmission electron tomography in the SEM is presently under development.
Moreover, an innovative multi-purpose platform for in-situ TEM measurements is under development. It is based on a “in-house” designed and fabricated innovative MEMS/NEMS-based sample holder, abele to provide electrical contacts and actuate micromachined systems during observation: the mechanical, electrical and thermal properties of the nanomaterials will be measured and verified together with their structural and compositional characteristics.
Contact person: Vittorio Morandi
Finally, electron beams with variable azimuthal angular momentum are obtained in a TEM using phase and amplitude/phase electron holograms that are realized by means of FIB milling or electron beam lithography. This special kind of beams can be applied to the study of magnetic properties of materials.
On the modeling side, the research activiy is mainly based on the Density Functional Theory (DFT), that is a widely used framework for quantitative calculations in realistic materials with moderate correlations in which the interacting electrons are treated quantum mechanically. First, we perform preliminary validation of correct exchange-correlation functional and relative pseudopotential even for non-bonding, dispersive, interactions. Then we impose or relax the most appropriate atomic configuration for a specific sample under consideration, may it be stacked graphene layers, nanotubes or folded graphene edges in which local charge re-distributions may play an important role for functionalization. Finally, we estimate the various contributions to internal potentials and charge fields to carry on a direct comparison with electron microscopy response, in particular the phase shift measured in electron holography so to validate this technique in case of thin samples with some unknown structural features.
Contact person: Cristian Degli Esposti Boschi