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.

1. Development of HIPIMS Technology for
Superconducting Coated Cavities
G. Terenziani, S.Calatroni, A. P. Ehiasarian, T. Junginger, S. Aull

2. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

3. From DCMS To HiPIMS
© Andre Anders, 2010
11
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

4. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

5. HIPIMS Samples – Optical Emission
Spectroscopy (OES)
50 88 125 165 180 270 340 410 480 550
85
69
53
37
21
Vacuum, Surfaces & Coatings Group
Technology Department
Pulse Duration (μs)
Peak Current (A)
0.05000
0.1250
0.2000
0.2750
0.3500
0.4250
0.5000
0.5750
0.6500
Nb II / Nb I Ratio
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
12

6. HIPIMS Samples – Optical Emission
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
Ratios (Nb+/Nb) vs Peak Current Density @ different
Vacuum, Surfaces & Coatings Group
Technology Department
Spectroscopy (OES)
0
pulse width
0 0.2 0.4 0.6 0.8 1 1.2
Ratio Nb+/Nb
Current Density (A*cm-2)
Ratio I @ 50 us
Ratio I @ 200 us
Ratio I @ 550 us
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
13

7. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

8. HIPIMS Samples – Mass Spectrometer
1000000
100000
10000
1000
100
10
(MS) – Nb+ case – 0.5 Acm-2
Zone I Zone II
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
Vacuum, Surfaces & Coatings Group
Technology Department
Equation y = a + b*x
Weight No Weighting
Residual
Sum of
Squares
0 20
1000000
100000
10000
1000
100
10
1
Intensity
Energy
0.03801
Pearson's r -0.99042
Adj. R-Squar 0.98028
Value Standard Erro
Intensity
Intercept 5.44624 0.02626
Slope -0.2808 0.00727
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
0 20
1000000
100000
10000
1000
100
10
1
Intensity
Energy
0.37334
Pearson's r -0.99248
Adj. R-Square 0.98487
Value Standard Erro
Intensity
Intercept 4.86924 0.02183
Slope -0.16911 0.0021
0 20
1
Intensity
Energy
0.03287
Pearson's r -0.99008
Adj. R-Square 0.97922
Value Standard Error
Intensity
Intercept 5.87232 0.01752
Slope -0.46038 0.01499
Zone III
59.5% 29%
11%
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
15

9. HIPIMS Samples – Mass Spectrometer
(MS) – Nb+ case – 1.3 Acm-2
Zone I Zone II
Equation y = a + b*x
Weight No Weighting
Residual
Sum of
Squares
0 20
1000000
100000
10000
1000
100
10
1
Vacuum, Surfaces & Coatings Group
Technology Department
Intensity
EnergyeV
0.01586
Pearson's r -0.98183
Adj. R-Squar 0.96
Value Standard Erro
Intensity
Intercept 5.97114 0.02368
Slope -0.6212 0.04002
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
0 20
1000000
100000
10000
1000
100
10
1
Intensity
EnergyeV
0.01039
Pearson's r -0.99757
Adj. R-Square 0.99498
Value Standard Error
Intensity
Intercept 5.68381 0.01009
Slope -0.29305 0.0038
Equation y = a + b*x
Weight No Weighting
Residual
Sum of
Squares
0 20
1000000
100000
10000
1000
100
10
1
Intensity
EnergyeV
0.17679
Pearson's r -0.99539
Adj. R-Squar 0.99071
Value Standard Erro
Intensity
Intercept 5.08897 0.01364
Slope -0.1489 0.00144
Zone III
49.5% 33.3%
12%
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
16

10. HIPIMS Samples – Mass Spectrometer
(MS) – Nb+ case – 2 Acm-2
Equation y = a + b*x
Weight No Weighting
Residual Sum of
Squares
Zone I Zone II
0 5 10 15 20 25 30
1000000
100000
10000
1000
100
10
1
Vacuum, Surfaces & Coatings Group
Technology Department
Intensity
Energy
0.01735
Pearson's r -0.98468
Adj. R-Square 0.96621
Value Standard Error
Intensity
Intercept 6.01073 0.02477
Slope -0.70913 0.04186
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
0 10 20 30
1000000
100000
10000
1000
100
10
1
Intensity
Energy
0.26334
Pearson's r -0.99737
Adj. R-Square 0.99471
Value Standard Error
Intensity
Intercept 5.37594 0.00808
Slope -0.14611 9.00585E-4
Equation y = a + b*x
Weight No Weighting
Residual Sum of
Squares
0 20
1000000
100000
10000
1000
100
10
1
Intensity
Energy
1.65281
Pearson's r -0.97238
Adj. R-Square 0.94526
Value Standard Error
Intensity
Intercept 4.16017 0.02843
Slope -0.06511 0.00111
Zone III
48.4%
50.6%
1%
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
17

11. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

12. DCMS Cross Section Structure
Vacuum, Surfaces & Coatings Group
Technology Department
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
22
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.

13. Vacuum, Surfaces & Coatings Group
Technology Department
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
23
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.

14. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

15. HIPIMS Samples – X-Ray Diffraction
Vacuum, Surfaces & Coatings Group
Technology Department
Cu <200>
Cu <200>
Cu <200>
Nb <110>
Nb <110>
Nb <110>
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
25

16. HIPIMS Samples – X-Ray Diffraction
25
20
15
10
5
Vacuum, Surfaces & Coatings Group
Technology Department
6
5
4
3
2
1
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
26
0
0
0 0.5 1 1.5 2 2.5
Thickness (um)
Ratio Nb <110> / Cu <200>
Current Density (A/cm2)
Ratio
Sample Thickness

17. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

18. HIPIMS Samples – Residual
Resistance Ratio (RRR)
25
20
15
10
5
Comparison RRR Vs Crcistallographic Orientation
Vacuum, Surfaces & Coatings Group
Technology Department
25
20
15
10
5
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
28
0
0
0 0.5 1 1.5 2 2.5 3
Nb <110> / Cu <200>
RRR
Current Density (A/cm2)
RRR Vs Current Density @200 us
Nb <110> / Cu <200>

19. Outline
• From Dc Magnetron Sputtering to HiPIMS
• HIPIMS Samples Analysis:
OES
MS
SEM
XRD
RRR
• HIPIMS Cavity Results

20. HIPIMS on 1.3 GHz Cavity – Deposition System
Vacuum, Surfaces & Coatings Group
Technology Department
1.3 GHz Cavity
Magnet
Central Cathode
413 mm
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
30

21. HIPIMS on 1.3 GHz Cavity M2.3 – R
Vacuum, Surfaces & Coatings Group
Technology Department
s
Vs T
Δ/kb = 18 K
RRR = 13.1
RRES = 4.5 nΩ
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
31
J = 2 A/cm2, τ = 200 us
Surface treatment: EP + SUBU

22. HIPIMS on 1.3 GHz Cavity M2.7 – R
Vacuum, Surfaces & Coatings Group
Technology Department
s
Vs T
Δ/kb = 18 K
RRR = 15
RRES = 6.5 nΩ
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
32
J = 2 A/cm2, τ = 200 us
Surface treatment: EP

23. HIPIMS on 1.3 GHz Cavity M2.7 – R
Vacuum, Surfaces & Coatings Group
Technology Department
s
Vs
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
33
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%)
E
acc

24. HIPIMS on 1.3 GHz Cavity - Results
Vacuum, Surfaces & Coatings Group
Technology Department
G. Terenziani, S. Calatroni, A.P. Ehisarian, T.
Junginger
34

25. Thank you for your attention