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Chemical-physical design of metallic interfaces for alloys production and composite materials

High-tech devices require the development of components with different structures and complementary properties that are assembled into a final product either mechanically or by physical-chemical processes related to the tailoring of interfaces and design of novel structural and functional materials. The key role of interfaces and surfaces in determining performances and reliability of a new composite multilayer material is evident.

For example, in the field of microelectronics, there are numerous research activities aimed to increase the performances of miniaturized integrated circuits, such as diodes and field effect transistors (FET). Taking into account the outstanding properties of graphene, it has been demonstrated that, in such devices, the modification of the interfaces through the addition of graphene layers, their performances were substantially improved. It is therefore clear the fundamental role of the interfaces, such as e.g. metal-graphene-graphene-metal or metal-graphene-ceramic, that need to be optimized to meet the required characteristics. In this framework, the research activity is focused primarily to define the "transparency to the wettability" of graphene from molten metals or alloys, when a layer (or layers) of graphene coat a refractory material. If the new property of graphene will be confirmed, it may result in marked effects on the properties of both the joints and components, and as the consequence, it can be strictly linked to the optimization of soldering processes. However, another aspect that involves the liquid / gas interfaces has to be considered in the soldering processes.

  • Basic concept of a single transistor, similar to a metal-semiconductor field-effect transistor: graphene forms the source, drain and gate electrode, and the SiC substrate is the semiconducting transistor channel.
  • Scheme of a liquid metal sessile drop on SiC substrate coated by one or more graphene layers.

The presence of oxygen in solder alloys (typically SAC systems, i.e. the Sn-Ag-Cu) and surrounding atmospheres and how it affects the quality of the process, in terms of microstructure, adhesion, mechanical and electrical properties has become one of the most important issues.
Another example that highlights the importance of interfaces in Materials Design is the manufacturing of CMOS (complementary metal-oxide semiconductor) devices and sensors where composite materials, such as Ir, Co are in contact with SiC or vitreous C, are used. Studies on the wetting properties of those materials are performed. Thus, the present research aims to develop new composite materials in terms of the surface and interface properties.

  • EXPERTISE:
    • Surface properties of metallic systems at high temperature and their sensitivity to reactive gases contamination: transport models at the metal liq / gas describing the effects of oxygen on the surface properties for the optimization of metallurgical processes (casting, soldering, etc..)
    • Study of the wetting properties of liquid metal/graphene/ SiC systems.
    • Study of kinetic and reactive wettability of composite materials, candidates for the fabrication of CMOS devices (complementary metal-oxide semiconductor) and sensors (Ir, Co vs SICC, Glassy-C).
Oxygen tensioactive effects on the surface tension of Ag-Cu alloys for different compositions: the experimental data fully validate the theoretical curves predicted by the transport model
Wetting experiment by dispensed drop: Si-Co alloy drop is squeezed and dispensed on Glassy-C substrate. The interface obtained is analyzed by SEM/EDX.
  • KEYWORDS:
    liquid metals and alloys interfaces surfaces surface tension reactive wetting and interfacial reaction kinetics thermodynamic models oxidation transport models liq / gas casting infiltration
  • RECENT PUBLICATIONS:
    • M. Caccia, S. Amore, D. Giuranno, R. Novakovic, E. Ricci, J. Narciso
      Towards optimization of SiC/CoSi 2 composite material manufacture via reactive infiltration: Wetting study of Si–Co alloys on carbon materials
      J of the European Ceramic Society, 35 (2015) 4099–4106.
    • E. Ricci, S. Amore, D. Giuranno, R. Novakovic, A. Tuissi, N. Sobczak, R. Nowak, G. Bruzda
      Surface tension and density of Si-Ge melts
      J. Chem. Phys. 140, (2014) 214704.
    • E. Arato, M. Bernardi, D. Giuranno, E. Ricci
      Surface oxidability of pure liquid metals and alloys
      App Surf Sci, 258 (7) (2012) 2686 – 2690.
    • E. Ricci, D. Giuranno, N. Sobczak
      Further development of testing procedures for high temperature surface tension measurements
      J of Mat Eng and Perf, 22 (11) 3381 (2013)
  • PROJECTS:
    • MAP-ESA/ASI OXYTHERM:Thermophysical Properties of Liquid Alloys under Oxygen Influence
    • MAP-ESA/ASI THERMOPROP:Thermophysical Properties of Liquid Metals for Industrial Process Design
    • MAP-ESA/ASI SEMITHERM:Investigation of Thermophysical properties of Liquid Semiconductors
    • FLAG-ERA JTC 2015 GRAPHENWET-The effect of wetting transparency of graphene in manufacturing of electronics components such as Field-Effect Transistor” Research Proposal
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