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HIPIMS is gaining large consensus around the world as a possible solution to overcome the problems faced with standard dcMS for the superconductive thin film coatings on copper RF cavities. Given the wide parameter space available with HIPIMS it is informative to draw out th relationship between plasma parameters microstructure and quality of the film produced. Influence of different discharge settings (pulse width, current density and frequency) has been studied in order to improve film performance. Samples have been produced in order to analyse the film microstructure, correlated to the plasma parameters, as well as superconductive properties. The microstructure showed an interesting behaviour, with the grain size increasing with the peak discharge current; the Residual Resistance Ratio (RRR) is inversely proportional to the current for short pulse widths, while it is directly proportional to the current for longer pulse widths. This seems to be related to an increasing number of grains with (110) crystallographic orientation in the deposited film. The performance of superconductive cavities produced with HIPIMS is comparable with some of the best dcMS coated ones. Interesting results are obtained with OES and MS comparing argon and krypton process gases. In particular more energetic ions are produced when using krypton as process gas due to the longer mean free path for elastic collisions for the same pressure. Experiments on cavities have been conducted at CERN while samples have been prepared both at Sheffield Hallam University and at CERN. This allows us to make a comparison between the two different experimental setups. Results on plasma analysis, superconductive properties and film morphology will be presented as well as the performance of the latest HIPIMS-coated cavities.
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Development of HIPIMS Technology for Superconducting Coated Cavities
G. Terenziani, S.Calatroni, A. P. Ehiasarian, T. Junginger, S. Aull
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
From DCMS To HiPIMS
© Andre Anders, 201011
Generalized Structure Zone Diagram
A. Anders, Thin Solid Films 518, 4087 (2010).
derived from Thornton’s diagram, 1974
Based on “Structure Zone Model” - Thornton, J.Vac. Sci. Technol. 11 (1974) 666
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er12
HIPIMS Samples – Optical Emission Spectroscopy (OES)
50 88 125 165 180 270 340 410 480 550
21
37
53
69
85
Pulse Duration (µs)
Pe
ak
Cu
rre
nt
(A)
0.05000
0.1250
0.2000
0.2750
0.3500
0.4250
0.5000
0.5750
0.6500
Nb II / Nb I Ratio
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er13
HIPIMS Samples – Optical Emission Spectroscopy (OES)
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.20
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Ratios (Nb+/Nb) vs Peak Current Density @ dif-ferent pulse width
Ratio I @ 50 us
Ratio I @ 200 us
Ratio I @ 550 us
Current Density (A*cm-2)
Rati
o N
b+
/Nb
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er15
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.03801
Pearson's r -0.99042
Adj. R-Squar 0.98028
Value Standard Erro
IntensityIntercept 5.44624 0.02626
Slope -0.2808 0.00727
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.37334
Pearson's r -0.99248
Adj. R-Square 0.98487
Value Standard Erro
IntensityIntercept 4.86924 0.02183
Slope -0.16911 0.0021
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.03287
Pearson's r -0.99008
Adj. R-Square 0.97922
Value Standard Error
IntensityIntercept 5.87232 0.01752
Slope -0.46038 0.01499
Zone I Zone II
Zone III
HIPIMS Samples – Mass Spectrometer (MS) – Nb+ case – 0.5 Acm-2
59.5% 29%
11%
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er16
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
EnergyeV
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.01586
Pearson's r -0.98183
Adj. R-Squar 0.96
Value Standard Erro
IntensityIntercept 5.97114 0.02368
Slope -0.6212 0.04002
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
EnergyeV
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.01039
Pearson's r -0.99757
Adj. R-Square 0.99498
Value Standard Error
IntensityIntercept 5.68381 0.01009
Slope -0.29305 0.0038
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
EnergyeV
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.17679
Pearson's r -0.99539
Adj. R-Squar 0.99071
Value Standard Erro
IntensityIntercept 5.08897 0.01364
Slope -0.1489 0.00144
Zone I Zone II
Zone III
HIPIMS Samples – Mass Spectrometer (MS) – Nb+ case – 1.3 Acm-2
49.5% 33.3%
12%
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er17
0 5 10 15 20 25 301
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.01735
Pearson's r -0.98468
Adj. R-Square 0.96621
Value Standard Error
IntensityIntercept 6.01073 0.02477
Slope -0.70913 0.04186
0 10 20 301
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.26334
Pearson's r -0.99737
Adj. R-Square 0.99471
Value Standard Error
IntensityIntercept 5.37594 0.00808
Slope -0.14611 9.00585E-4
0 201
10
100
1000
10000
100000
1000000
Inte
nsity
Energy
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
1.65281
Pearson's r -0.97238
Adj. R-Square 0.94526
Value Standard Error
IntensityIntercept 4.16017 0.02843
Slope -0.06511 0.00111
Zone I Zone II
Zone III
HIPIMS Samples – Mass Spectrometer (MS) – Nb+ case – 2 Acm-2
48.4%50.6%
1%
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er22
DCMS Cross Section Structure
1 um
Cu
Nb
C
Surface features in HIPIMS seem larger than in DCMS but the column size in cross section appears smaller in HIPIMS. The large surface features in HIPIMS could be comprised of several columns whose inter-columnar boundaries are so dense that they appear as single crystals.
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er23
Cross Section Structure - Comparison
In neither DCMS nor HIPIMS there doesn't seem to be a large-scale epitaxial growth of the films. Rather, the growth in both cases starts out with numerous nucleation sites probably with different grain orientation and the subsequent growth is a competition between different grain orientations.
In HIPIMS it seems that near the coating-substrate interface there is a thicker region where there is competitive growth. This is followed by a process of grain selection where winning grains widen to take up the entire area.
It could be speculated that during the selection process, DCMS grains do not densify their grain boundaries whilst HIPIMS grains can do that due to the extra surface mobility of metal ions.
Because of this the morphology of the HIPIMS surface appears to contain larger features than DCMS.
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er25
HIPIMS Samples – X-Ray Diffraction
Cu <200>
Cu <200>
Cu <200>
Nb <110>
Nb <110>
Nb <110>
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er26
HIPIMS Samples – X-Ray Diffraction
0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.20
5
10
15
20
25
0
1
2
3
4
5
6
RatioSample Thickness
Current Density (A/cm2)
Ratio
Nb
<110
> /
Cu <
200>
Thic
knes
s (u
m)
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er28
HIPIMS Samples – Residual Resistance Ratio (RRR)
0.5 1 1.5 2 2.5 30
5
10
15
20
25
0
5
10
15
20
25
Comparison RRR Vs Crcistallographic Orientation
RRR Vs Current Density @200 usNb <110> / Cu <200>
Current Density (A/cm2)
RRR
Nb <110> / Cu <200>
Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OESMSSEMXRDRRR
• HIPIMS Cavity Results
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er30
HIPIMS on 1.3 GHz Cavity – Deposition System
1.3 GHz Cavity
Magnet
Central Cathode
413 mm
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er31
HIPIMS on 1.3 GHz Cavity M2.3 – Rs Vs T
Δ/kb = 18 KRRR = 13.1RRES = 4.5 nΩ
J = 2 A/cm2, τ = 200 usSurface treatment: EP + SUBU
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er32
HIPIMS on 1.3 GHz Cavity M2.7 – Rs Vs T
Δ/kb = 18 KRRR = 15RRES = 6.5 nΩ
J = 2 A/cm2, τ = 200 usSurface treatment: EP
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er33
There is an increase of about 15 nΩ from low field to 15 MV/m between the curves measured just below and just above λ transition Q-slope is influenced by thermal boundary, but it is not the dominant effect (≈7%)
HIPIMS on 1.3 GHz Cavity M2.7 – Rs Vs Eacc
Vacuum, Surfaces & Coatings GroupTechnology Department G. Terenziani, S. Calatroni, A.P. Ehisarian, T. Junging
er34
HIPIMS on 1.3 GHz Cavity - Results
Thank you for your attention
