Effect of magnetic field on spoke behaviour in HiPIMS plasma

Hnilica, Jaroslav; Klein, Peter; Šlapanská, Marta; Fekete, Matej; Vašina, Petr

doi:10.1088/1361-6463/aaa7d3

Cited by 33 publications

(57 citation statements)

References 37 publications

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“…This observation can be correlated to the change in the magnetic field configuration in the corners compared to the straight parts of the rectangular target. Hnilica et al have shown that increasing the magnetic field strength increases the spoke mode number [24], which is consistent with the observation of the spoke "bunching" in the curved parts of the magnetron. An increase in plasma power may cause the length of the spokes to become shorter in case of chromium or longer in case of titanium as target material.…”

Section: Spokes In Hipims Plasmas On Rectangular Magnetronssupporting

confidence: 71%

Spokes in high power impulse magnetron sputtering plasmas

Hecimovic

Keudell²

2018

J. Phys. D: Appl. Phys.

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High power impulse magnetron sputtering (HiPIMS) is a deposition technique where a metal magnetron target is sputtered in a high density plasma to synthesize thin layers with superior properties on a substrate material. These plasmas are characterised by short pulses in the range of 50 µs to 200 µs and very high peak powers in the range of several kW/cm 2 per target area. The understanding of these dynamic plasmas is of upmost interest for the further development of this coating technique. Fast camera measurements revealed the formation of localised ionisation zones in these plasmas that propagate with a velocity of the order km/s. In the case of a circular magnetron, the movement of these ionisation zones appears like the movement of a set of spokes, which led to this common expression spoke to illustrate the pattern formation in these high density plasmas. The analysis and understanding of the spoke phenomenon is still a matter of an open debate, because the analysis and the theoretical description is hampered by the inherent complexity of these plasmas. In this paper, we review the experimental observations of the spoke phenomenon and highlight several approaches for their theoretical explanation.

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Section: Spokes In Hipims Plasmas On Rectangular Magnetronssupporting

confidence: 71%

Spokes in high power impulse magnetron sputtering plasmas

Hecimovic

Keudell²

2018

J. Phys. D: Appl. Phys.

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“…The spoke parameters such as their shape, mode number (the number of spokes along the race track) or the propagation velocity were thoroughly determined. It has been discovered that the spoke properties are highly dependent on the discharge parameters [22][23][24], the target material [14,17,25] and the magnetic field strength [26]. In addition, the theoretical description of spokes has been presented in phenomenological models [13,14,[27][28][29][30], critical ionisation velocity models [31,32], kinetic models [33][34][35][36] or wave model [37].…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the non-invasive single-shot spatial-resolved optical emission spectroscopy (OES) was conducted in nonreactive HiPIMS discharge using a titanium target in the pressure range from 0.4 to 1.6 Pa, where only the localised, well-defined spokes are present [26]. The signals of the fast photo-diode and the cylindrical Langmuir probe were utilised to capture and determine the position of a passing spoke.…”

Section: Introductionmentioning

confidence: 99%

Single-shot spatial-resolved optical emission spectroscopy of argon and titanium species within the spoke

Šlapanská¹,

Kroker²,

Hnilica³

et al. 2021

J. Phys. D: Appl. Phys.

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The rotating plasma patterns, also known as ionisation zones or spokes, observed, among other discharges, in high power impulse magnetron sputtering discharge (HiPIMS) require non-invasive diagnostics favourable for a precise characterisation of their properties. In this contribution, the single-shot spatial-resolved optical emission spectroscopy of the spoke was conducted in non-reactive HiPIMS discharge using a titanium target. Investigated working pressures cover the conditions with the presence of localised, well-defined spokes. A fast photodiode and a cylindrical Langmuir probe were utilised to capture and determine the passing spoke position. These signals were synchronised with the acquisition of the optical emission spectrum by the intensified charge-coupled device detector. A large amount of single-shot data enabled the statistical analysis of the spoke. The optical emissions of argon atoms and ions and titanium atoms and ions were investigated in the passing spoke. It was found that the intensities of the spectral lines of the Ar and Ti species have the characteristic evolution for all studied spectral lines of this specific species within the spoke. The intensity evolutions are independent of the applied pressure. The evolution of the excitation temperatures determined by the Boltzmann plot method using the Ar II and Ti I and Ti II spectral lines remains constant within the spoke in the margin of standard error for all investigated pressures.

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“…The spoke has been well characterized within a number of experimental devices, including Hall thrusters [3,4,5,6,7,8,9,10,11,12,13,14,15], planar magnetrons [16,17,18,19,20,21,22,23], cylindrical magnetrons [24,25] and Penning discharges [26,27,28]. These devices feature cylindrical geometry, with electron drift and spoke propagation occurring in the azimuthal direction.…”

Section: Introductionmentioning

confidence: 99%

Scaling of spoke rotation frequency within a Penning discharge

et al. 2018

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A rotating plasma spoke is shown to develop in two-dimensional full-sized kinetic simulations of a Penning discharge cross-section. Electron cross-field transport within the discharge is highly anomalous and correlates strongly with the spoke phase. Similarity between collisional and collisionless simulations demonstrates that ionization is not necessary for spoke formation. Parameter scans with discharge current I d , applied magnetic field strength B and ion mass m i show that spoke frequency scales with eE r L n /m i , where E r is the radial electric field, L n is the gradient length scale and e is the fundamental charge. This scaling suggests that the spoke may develop as a non-linear phase of the collisionless Simon-Hoh instability.

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Effect of magnetic field on spoke behaviour in HiPIMS plasma

Cited by 33 publications

References 37 publications

Spokes in high power impulse magnetron sputtering plasmas

Spokes in high power impulse magnetron sputtering plasmas

Single-shot spatial-resolved optical emission spectroscopy of argon and titanium species within the spoke

Scaling of spoke rotation frequency within a Penning discharge

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