3D Plasma-sheath-lenses: phenomenology and applications

This dissertation is a synopsis of research publications on phenomenology and applications of 3D plasma-sheath-lenses. It is demonstrated that the sheath surrounding electrodes interfacing with insulators acts as an electrostatic lens, focusing positive or negative charges to distinct locations on the electrode surface depending on the entrance coordinates at the sheath edge. Two ion focusing effects have been discovered. The discrete focusing leads to the formation of a passive surface, while the modal focusing results in the formation of certain ‘modal spots’ and/or ‘modal lines’. The very well-defined pat­terns revealed by the focusing effects open new possibilities in plasma and sheath diagnostics, directly correlating with ion-induced surface modifications. By custom­izing 3D plasma-sheath-lenses one can manipulate ion kinetics to induce desired ion optics, which, in combination with magnetic fields, provides significant flex­ibility for various applications, including focused ion beam extraction, mass spec­trometry, plasma immersion ion implantation, and new sensors for negative ions. In the last chapter, the pioneering concept of 3D plasma-sheath-lenses is further extended to negative ion focusing during magnetron sputtering. New develop­ments are anticipated to improve the correlation between simulations and experi­ments, encompassing time-dependent processes or other intricate details.