Plasmas as Sources of Nanostructured Materials: Plasma-Assisted Supersonic-Jet Deposition

We review the application of plasma techniques to create new advanced materials displaying scale-invariance properties down to the nanoscale. The aim is to describe in sufficient detail to a general reader the principles and effective implementation of the plasma-assisted supersonic jet deposition (PA-SJD) technique. Indeed, its popularity has been increasing during the last decades as a result of its precision and easy controllability in the fabrication of thin films, yielding both a broad range of widths and a variety of morphologies. The presentation puts emphasis on the different processes taking place in the plasma chamber, where the nanoparticles constituting the building blocks of the film are generated, as well as on the behavior in both space and time of the supersonic jet inside the deposition chamber. In the latter, the supersonic jet carries the nanoparticles which impact onto a substrate, on top of which a growing nanostructured thin film is deposited. In addition to the description of the experimental set-up and results, Monte Carlo (MC) simulations are discussed illustrating the dynamics and expansion of Ar+ ions in a pure argon plasma, that is without the presence of a precursor for generating nanoparticles. The chapter closes with a description of the different morphologies effectively produced in the laboratory using TiO2-based nanoparticles as the building blocks of the deposited thin films.