Integrated ion flux emitted from the cathode spot region of a diffuse vacuum arc

The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique similar to a method originally proposed by Yushkov. The measuring principle makes use of the welljustified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged source intensity (i.e., emission of ions from cathode spots) is constant until the arc is rapidly switched off. In the experiment, arc termination took about 700 ns, which is much faster than the decay of the ion current measured at the collector placed in more than 2 meters distance from the cathode. The experimental distribution functions for most cathode materials show one large peak with a tail and one or more small peaks at higher ion velocities. The distribution functions for some other materials exhibit several peaks. No conclusive answer can be given about the nature of these peaks. Arguments are presented that the peaks are not caused by different charge states or plasma contamination but rather due to insufficiently averaged source fluctuations and/or acceleration by plasma instabilties.a Author to whom correspondence should be addressed; electronic mail: aanders@lbl.gov 2

Section: Resultssupporting

confidence: 70%

Ion energy distribution functions of vacuum arc plasmas

Byon

Anders

2003

“…To gain additional information on the plasma parameters and their change with pressure, the smoothened IEDs of the metal ions were fitted by shifted Maxwellian distributions (SMD), as suggested by Kutzner et al 25 The approach was also adopted by Bilek et al to describe the IEDs of Ti + in a nitrogen environment, 14 and by Rosén et al to investigate IEDs of Al ions in vacuum. 6 The forward ion flux distribution of a SMD can be written as (units of energy and temperature in eV)…”

Section: Resultsmentioning

confidence: 99%

Influence of argon and oxygen on charge-state-resolved ion energy distributions of filtered aluminum arcs

Rosén

Anders

Mráz

et al. 2006

The charge-state-resolved ion energy distributions (IEDs) in filtered aluminum vacuum arc plasmas were measured and analyzed at different oxygen and argon pressures in the range 0.5 -8.0 mTorr. A significant reduction of the ion energy was detected as the pressure was increased, most pronounced in an argon environment and for the higher charge states. The corresponding average charge state decreased from 1.87 to 1.0 with increasing pressure. The IEDs of all metal ions in oxygen were fitted with shifted Maxwellian distributions. The results show that it is possible to obtain a plasma composition with a narrow chargestate distribution as well as a narrow IED. These data may enable tailoring thin-1 film properties through selecting growth conditions that are characterized by predefined charge state and energy distributions.2

“…IV, assuming that the plasma density is n 0 ¼ 10 17 m À3 , ion mass is M ¼ 48 Â 1.67 Â 10 À27 kg (titanium), and initial ion energy is E ion0 ¼ 50 eV. 48,49 The set of the calculated paths is shown in Fig. 8(a) for the B g "B m2 " configuration, in Fig.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…At the same time, the ions that exit the plasma source with kinetic energy E ion0 pass the magnetic trap without any significant changes in their motion. 48,49 However, the ions are affected by the negative space developed in the magnetic trap. The magnetic fields were calculated, and the regions of the magnetic traps were detected.…”

Section: Modelmentioning

confidence: 99%

Control of ion density distribution by magnetic traps for plasma electrons

Baranov

Romanov

Fang

et al. 2012

The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.