Speaker
Description
Physical vapor deposition (PVD) is a vacuum-growth method that allows the deposition of thin films and coatings on a substrate by physically vaporizing a source material and condensing it on the substrate [1]. PVD systems are of pivotal importance in many science and technology fields creating coatings that enhance a material's hardness, wear resistance, and appearance as well as constitute the active material themselves (e.g. in tandem photovoltaic cells). In many of such technique’s plasma, more specifically low temperature plasma, plays a fundamental role.
As an example, magnetron sputtering deposition system exploits a magnetically confined glow discharge plasma used to erode the source material ejecting atoms. The inhomogeneous magnetic field traps electrons near the target, increasing ionization and collisions with the sputtering gas, which leads to more efficient plasma generation and higher deposition rates. The high-power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth, down to the nanoscale, by controlling the energy and direction of the deposited species [2].
Also, in Pulsed Laser Deposition (PLD) the plasma generated during the laser matter interaction tailors the energy of the ejected species determining the features of the growing film. More interestingly depending on the ablation regime (femtosecond or nanosecond) completely different laser plasma scenarios are determined in terms of plasma density and temperature. In the nanosecond regime both ions and electrons interact with the laser pulse. In the fs regime laser matter interaction is only related to electrons being the ions still “frozen” in the crystal lattice. Such differences lead to completely different ablation dynamics that result in the ablation of atomic species or nanoparticles in the two above mentioned regimes [3,4].
In this contribution, we present the work performed at Politecnico di Milano and Nanolab showing the role of plasma parameters in determining the features of deposited films dealing with HiPIMS and PLD both in fs and ns regimes. We will show examples taken from the energy materials branch (i.e. fusion and fission coatings, photovoltaics and materials for laser driven ion acceleration). Finally, some of the models that have been developed to gain understanding of the discharge processes will be presented.
Reference:
[1] Zhenmin Li, Baosen Mi, Xun Ma, Ping Liu, et al. Chem. Eng. Journal, 477, 2023
[2] J. T. Gudmundsson, N. Brenning, D. Lundin, et al., J. Vac. Sci. Technol. A, 30, 2012
[3] J. M. Conde Garrido, J. M. Silveyra, Optics and Lasers in Engineering, 168, 2023
[4] S. Amoruso, G. Ausanio, R. Bruzzese, M. Vitiello, Phys. Rev. B, 71, 2005
