The characteristic shape of emission profiles of plasma spokes in HiPIMS: the role of secondary electrons

Hecimovic, A.; Gallian, Sara; Brinkmann, R. P.; Böke, Marc; Winter, J.

doi:10.1088/0022-3727/47/10/102003

Cited by 56 publications

(86 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[12][13][14][15][16] We stress that spoke motion does not imply motion of plasma but rather a displacement of a region of enhanced ionization rate. The spoke velocity is therefore a phase velocity, and not a group velocity.…”

mentioning

confidence: 84%

Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

Yang

Zhou

Liu

et al. 2016

Applied Physics Letters

View full text Add to dashboard Cite

We present evidence for breathing modes in magnetron sputtering plasmas: periodic axial variations of plasma parameters with characteristic frequencies between 10 and 100 kHz. A set of azimuthally distributed probes shows synchronous oscillations of the floating potential. They appear most clearly when considering the intermediate current regime in which the direction of azimuthal spoke motion changes. Breathing oscillations were found to be superimposed on azimuthal spoke motion. Depending on pressure and current, one can also find a regime of chaotic fluctuations and one of stable discharges, the latter at high current. A pressure-current phase diagram for the different situations is proposed.

show abstract

mentioning

confidence: 84%

Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

Yang

Zhou

Liu

et al. 2016

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…Several authors studied the temporal fluctuations in the floating potential and some associated it with the moving ionization zones. 8,[33][34][35][36][37] Such measurements are relatively simple but offer a little insight into the properties of plasma since the motion of charged particles is affected by the gradient of the plasma potential and not by the gradient of the floating potential.…”

Section: Introductionmentioning

confidence: 99%

Plasma potential of a moving ionization zone in DC magnetron sputtering

Panjan

Anders

2017

Journal of Applied Physics

View full text Add to dashboard Cite

Using movable emissive and floating probes, we determined the plasma and floating potentials of an ionization zone (spoke) in a direct current magnetron sputtering discharge. Measurements were recorded in a space and time resolved manner, which allowed us to make a three-dimensional representation of the plasma potential. From this information we could derive the related electric field, space charge, and the related spatial distribution of electron heating. The data reveal the existence of strong electric fields parallel and perpendicular to the target surface. The largest E-fields result from a double layer structure at the leading edge of the ionization zone. We suggest that the double layer plays a crucial role in the energization of electrons since electrons can gain several 10 eV of energy when crossing the double layer. We find sustained coupling between the potential structure, electron heating, and excitation and ionization processes as electrons drift over the magnetron target. The brightest region of an ionization zone is present right after the potential jump, where drifting electrons arrive and where most local electron heating occurs. The ionization zone intensity decays as electrons continue to drift in the Ez × B direction, losing energy by inelastic collisions; electrons become energized again as they cross the potential jump. This results in the elongated, arrowhead-like shape of the ionization zone. The ionization zone moves in the –Ez × B direction from which the to-be-heated electrons arrive and into which the heating region expands; the zone motion is dictated by the force of the local electric field on the ions at the leading edge of the ionization zone. We hypothesize that electron heating caused by the potential jump and physical processes associated with the double layer also apply to magnetrons at higher discharge power, including high power impulse magnetron sputtering.

show abstract

“…12 In this contribution, the idea of presheath heating of electrons 12 is examined on a local level, and it is shown that there is a interdependence between presheath heating of electrons, the formation (and disappearance) of ionization zones 2-4 (a.k.a. spokes 11,16,17 ), and associated potential humps. 18 Fast imaging of HiPIMS [2][3][4]11,19 and direct current magnetron sputtering 20 (dcMS) plasmas indicated that ionization rate and emission of light and particles are usually not uniformly distributed but concentrated in bright zones that move along the racetrack.…”

mentioning

confidence: 99%

“…spokes 11,16,17 ), and associated potential humps. 18 Fast imaging of HiPIMS [2][3][4]11,19 and direct current magnetron sputtering 20 (dcMS) plasmas indicated that ionization rate and emission of light and particles are usually not uniformly distributed but concentrated in bright zones that move along the racetrack. Additionally, measurements of charged particle fluxes have revealed important features: (a) ion and electron fluxes appear in short pulses (jets), 21 (b) doubly charged ions have approximately twice the energy of singly charged ions, 18,21 and (c) ions emitted in the E× B direction have several 10 eV higher energy than ions going in the opposite direction, i.e., leaving the magnetron in the −E× B direction.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Anders

2014

Applied Physics Letters

View full text Add to dashboard Cite

The fundamental question of how energy is supplied to a magnetron discharge is commonly answered by the Penning-Thornton paradigm invoking secondary electrons. Recently, Huo and coworkers (Plasma Sources Sci. Technol. 22, 045005 (2013)) used a global discharge model to show that electron heating in the electric field of the magnetic presheath is dominant over heating by secondary electrons. In this contribution, this concept is applied locally taking into account the electric potential structure of ionization zones. Images of ionization zones can and should be interpreted as diagrams of the localization of high electric potential and related electron energy.

show abstract

The characteristic shape of emission profiles of plasma spokes in HiPIMS: the role of secondary electrons

Cited by 56 publications

References 14 publications

Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

Plasma potential of a moving ionization zone in DC magnetron sputtering

Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Contact Info

Product

Resources

About