Recent advances in vacuum arc ion sources

Abstract

Intense beams of metal ions can be formed fiom a vacuum arc ion source. This kind of source works well for most of the solid metals of the periodic table, and because the ions are in general multiply stripped with charge states as high as 4+ to 6+, the mean energy of the ion beam produced can be 100 -200 keV for extractor voltage in the comfortable range of about 50 -75 kV. Broadbeam extraction is convenient, and the time-averaged ion beam current delivered downstream can readily be in the tens of milliamperes range. The vacuum arc ion source has for these reasons found good .application for metallurgical surface modification -it provides relatively simple and inexpensive access to high dose metal ion implantation. Several important source developments have been demonstrated recently, including very broad beam operation, macroparticle removal, charge state enhancement, and formation of gaseous beams. We have made a very broad beam source embodiment with beam formation electrodes 50 cm in diameter (area 2000 cm2), producing a beam of width -35 cm for a nominal beam area of -1000 cm2, and a pulsed Ti beam current of about 7 A was formed at a mean ion energy of -100 keV. Separately, we've developed high efficiency macroparticle-removing magnetic filters and incorporated such a filter into a vacuum arc 1 ion source so as to form macroparticle-free ion beams. Jointly . IntroductionThe vacuum arc metal ion source provides a convenient and relatively inexpensive tool for carrying out metal ion implantation in a mode that is suitable for many different kinds of surface modification applications. High current beams of metal ions are formed from the dense, highly ionized metal plasma that is generated by a vacuum arc discharge embodied within the ion source configuration. The plasma physics of ion production in vacuum arc plasmas [l-41 and the approaches taken for incorporating this kind of plasma within an ion source 15-81 have been described in detail elsewhere. Vacuum-arc-based ion sources have been developed at many laboratories around the world [5,9], mostly for ion implantation and particle accelerator injection.As the subfield has grown and attracted workers to the area, so also the range of application variations, hardware embodiments, and performance objectives has expanded. Sources have been developed from very small up to quite large systems and with ion beam currents from a few milliamperes up to several amperes. More recently, a number of novel and advantageous source developments have been made. Here we report on several of these advances that are of particular relevance to ion implantation application. In the following, we firstly briefly review the fundamental characteristics of vacuum arc ion sources, and then describe some of the specific advances made together with the ion beam characterization results obtained . BackgroundThe vacuum arc ion source is, in essence, simplicity itself. A vacuum arc plasma source, typically but not necessarily of cylindrical symmetq and repetitively pulsed, is ap...

Hydrodynamic model for a vacuum arc operated with background gas: Theory and experimental validation

“…26 The fractions of Ti ions were taken as 0.11 for the z = + 1 , 0.77 for the z = + 2, and 0.12 for the z = + 3 ions. 27 It was also assumed that each metallic ion carried out an average kinetic energy of 122 eV at the cathode surface. 20 The electron temperature was chosen to be 2 eV at the cathode surface, in agreement with the experimental values in vacuum ͑see Fig.…”

Vacuum arc ion sources: recent developments and applications

“…Source cooling was improved over that of earlier versions, and so also the mean power dissipation capability. Upgrades to the Mevva-V that have been incorporated over the years include the addition of a small high-field pulsed solenoid around the arc region for charge state control, and the addition of a gas feed inlet to the arc region for the formation of hybrid metal-gas ion beams [54]. Interestingly, we note that the Mevva-V ion source has been operated as a high current electron source by simply changing the source bias from positive to negative [55], without any other change to the setup.…”

Raman spectra of partially oriented sp2 carbon films: Experimental and modelled

“…In previous work, we reported the preparation of carbon multilayer films with controlled stress levels prepared by cathodic arc deposition with a pulsed substrate bias [3,6,7]. This technique, variously known as plasma based ion implantation and deposition (PBIID) or plasma immersion ion implantation and deposition (PIIID) [8,9] involves high-energy implantation of a fraction of the deposited species, which facilitates intrinsic stress relief as the film is deposited. This allows much thicker films to be grown before the accumulated stress exceeds the adhesion limit delamination from the substrate occurs.…”