André Anders, Leibniz Institute of Surface Engineering (IOM) and University, Leipzig, Germany
Properties of coatings and thin films are primarily determined by their chemical composition and microstructure. In the simplest case, one uses substrate heating to affect the density (porosity) and crystallinity (i.e. amorphous vs. crystalline phases, possibly with a preferred orientation or texture). The involvement of plasmas and/or ion beams opens the possibility for non-equilibrium or atomic-scale heating, which can be very beneficial from several points of view, including, but not limited to, a reduction of the requirements on conventional substrate heating and cooling, the possibility to use temperature-sensitive substrates, the formation of otherwise unattainably phases, and the combination of deposition and etching effects. The key to non-equilibrium heating is specifically the kinetic ion energy, which can be controlled by the difference between surface potential and plasma potential, i.e., using suitable substrate and/or plasma biasing. When the kinetic ion energy exceeds the displacement energy, film growth can occur under the surface (very shallow ion implantation or “subplantation”), which is utilized, for example, in the deposition of diamond-like carbon. Biasing is often pulsed, which in combination with pulsed plasmas can be used for phased or species-selective control of ion energies, allowing us to synthesize non-equilibrium phases with new and interesting materials properties. In this talk, I will present in a systematic manner the concepts of non-equilibrium heating, the contributions of kinetic and potential energies of particles arriving at the surface of the growing film, and practical approaches to utilize the concepts for materials design in thin films and coatings.