Materials Production

Camilla Coletti

Crystal synthesis - Camilla Coletti

The scalable synthesis of highly crystalline graphene, other 2D materials and van der Waals heterostacks is of fundamental importance to develop a 2D-material based technology especially in the fields of electronics and optoelectronics.

 

Our research targets span from fundamental ones to strictly applicative ones. We are actively addressing the following objectives:

  • wafer scale integration of graphene
  • synthesis of vertical 2D heterostacks for optoelectronics and spintronics
  • study of fundamental properties of novel 2D transition metal dichalcogenides (TMDs)

In our laboratories we adopt a chemical vapor deposition (CVD) approach to synthesize 2D materials with exceptional electronic, optical and tribological properties. The synthetized materials are thouroughly investigated with advanced microscopic and spectroscopic techniques as well as via transport measurements. The structural and electronic properties of 2D materials and their heterostacks are tailored via atomic intercalation and the realization of superlattices. A strong collaboration is carried on with research groups involved in Graphene Flagship, in particular Spintronics (WP2), Photonics and Optoelectronics (WP8) and Wafer-scale System Integration (WP10).

Thanks to these activities, we have developed a rapid and industrially appealing CVD process for the synthesis of millimeter sized single-crystal graphene with remarkable transport properties (Miseikis et al., 2015). Furthermore we have recently presented a novel approach for the seeded growth of high-quality large single-crystal graphene (Miseikis et al., 2017). This deterministic growth approach is especially promising for wafer-scale integration of graphene. Also, we have realized via CVD 2D vertical heterostacks with atomically sharp interfaces such as graphene/hBN (Mishra et al., 2016), TMD/graphene and TMD/hBN. The latter displays exceptional optical properties such as a robust polarization conservation at room temperature (Rossi et al., 2016).

Connection with Graphene Flagship project

WP3 Enabling Materials

  • Task 3.1.3 Growth of transition metal dichalcogenides and black phosphorous with various and complementary techniques;
  • Task 3.1.4 Growth and characterization of single layer boron nitride (BN) and G/BN heterostructures;
  • Task 3.1.7 Growth and characterization of multilayered heterostructures G/2D, 2D/2D

(a)–(d) Proposed process flow for deterministic growth of single-crystal graphene. (e) SEM image of an array of graphene single-crystals. (f) Optical image of a graphene array on oxidised Cu foil. (g) Optical image of single-crystal array transferred on Si/SiO2 substrate with alignment markers. In figures (e)–(g) the array periodicity is 200 μm and crystal size is ~100 μm.

 

 

inks

Crystal exfoliation - Francesco Bonaccorso

Due to their exceptional (opto)electronic properties, graphene and other inorganic 2D materials can enhance the properties of the materials/devices they are integrated in. The development of industrially scalable methodology for the production of high-quality 2D material is therefore pivotal in view of large scale applications and industrialization.

 

Our research aims at the development of scalable production methods based on liquid phase exfoliation of layered materials to produce functional inks. These inks can be used for the design/realization of composite materials as well as active layers in (opto)electronic and energy devices, which can also be printed/realized on both rigid and flexible substrates.

We developed a method to exfoliate layered materials in liquid phase by wet-jet milling (patent application). The method allows us to produce crystal flakes with controlled morphology and rheological properties, compatible with any printing technologies. The high reproducibility and product yield enable cost-effective industrial-scale application: indeed, the first graphene motorbike helmet, in collaboration with MOMODESIGN, and the first shoes with graphene integrated, realized in collaboration with Fadel, are already on the market.

On the basis of the aforementioned results, our current research activity is focused on:

  • further refining the production methods;
  • extending our current techniques to the exfoliation of more exotic layered materials other than graphene and transition metal dichalcogenides, to obtain both inks or powders;
  • integrating the resulting inks and powders in innovative devices, towards application in composites, wearable electronics, flexible batteries and supercapacitors, and large area photovoltaics.

Connection with Graphene Flagship project

WP11 Energy generation: Synthesis and characterization of graphene and other inorganic 2D materials.

Objective: To formulate and provide the required quantities of graphene and other inorganic 2D material inks for the fabrication of printable solar cells and modules.

WP14 Polymer composites: Production of graphene and other inorganic 2D material-thermoplastic composites.

Objective: We will focus on the production of graphene and other inorganic 2D material masterbatches, i.e., polymeric pellets containing high concentrations of graphene and other inorganic 2D materials, which are the standard intermediates in the polymer supply chain.

2D materials: HRTEM images of hexagonal WSe<sub>2</sub> (left) and single-layer graphene (right, with Fourier transform in the inset).

Dispersions of different 2D crystals, from left to right: graphene, Bi<sub>2</sub>Te<sub>3</sub>,WS<sub>2</sub>, WS<sub>2</sub>, WS<sub>2</sub>, MoS<sub>2</sub> WSe<sub>2</sub>, phosphorene, MoO<sub>3</sub>, h-BN.