Material Science and Technology Research Group (STM)Dipartimento di Ingegneria Meccanica e Industriale
Università Roma TRE
Nano-mechanical and microstructural characterization of MS-PVD Nb thin films
Edoardo Bemporad, Marco Sebastiani, Fabio CarassitiGiulia Lanza and Enzo Palmieri
The fourth international Workshop on:THIN FILMS AND NEW IDEAS FOR PUSHING THE LIMITS OF RF
SUPERCONDUCTIVITYOctober 4-6, 2010
Legnaro National Laboratories (Padua) ITALY
www.stm.uniroma3.it
STM Roma TRE channel on YouTube Image Gallery Agilent Web seminar Interviews and videos on daily life at STM group
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
2
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
www.lime.uniroma3.itN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
3
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
RESONANT CAVITIES FOR PARTICLE ACCELERATORS
Very low Surface electrical
resistance (n a 1,8 K)
Bulk Niobium
Niobium Coated (PVD)Copper cavity
Lower costsHigher thermal stabilityBut…Significantly lower superconducting performances– WHY??
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
4
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
INTRODUCTION
5
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Many microstructural and morphological factors can affect the in-service performance of Nb coated OFHC Cu cavities (apart from impurities):
Roughness of the substrate; Morphology of coating/substrate interface; Coating thickness and thickness homogeneity; Coating density Grain size and crystals growth angle; Thickness and composition of the surface oxide layer Residual stress
All these aspects are related to the deposition parameters;
1999, Physica C 316 153–88
1997 , J. Appl. Phys. 81 (10) 6754
2005, J. Appl. Phys. 97 083904
2005, Thin Solid Films 489 56–62
1998, Appl. Surf. Sci. 126 219–30
2006, Physica C 441 79–82
INTRODUCTION
Quality control measurement (RRR and Tc) are usually performed on Nb film deposited on Quartz substrate RRR and Tc measured on Quartz are very useful
as threshold parameters;
Nevertheless, characterization methods are absolutely necessary to verify what are the micro-structural differences between coatings which are grown either on quartz or on copper
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
6
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Supercond. Sci. Technol. (21 (2008) 125026)
GAP OF KNOWLEDGE
7
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
A comprehensive chemical, morphological, and mechanical surface characterization can be useful, in order to find out the appropriate correlation function among process parameters/microstructure/surface properties and superconducting properties
In particular, the influence of the applied bias voltage on the functional and nano-mechanical properties of sputtered Nb thin films still needs to be deeply investigated.
Supercond. Sci. Technol. (21 (2008) 125026)
AIM OF THE WORK
8
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
To verify the influence of the applied bias voltage and nature of the substrate on the microstructural and nano-mechanical properties of MS-PVD Niobium thin films for use in superconducting resonant cavities for particle accelerators;
To establish a correlation between the functional performance (RRR and Tc) and the observed microstructural/mechanical properties;
To verify how nano-mechanical characterization can help in the characterization and quality control of such coatings
Supercond. Sci. Technol. (21 (2008) 125026)
Introduction and motivation
Brief Description of the adopted
characterization methodology
Results and discussion Conclusions
Evolution of characterization techniques and new potential of their synergic
uses
Nano-Indentatio
n
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
9
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
HARDNESS – SCALE OF INDENTATION
Macro-hardness
Micro-hardness
Nano-hardness
10 N 10 mN Load
10
ROMA TRE NANOHARDNESS TESTER
Berkovich tip
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
11
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
early 2008- CSM option- Lateral force measurement- Nano- positioninng stage
INSTRUMENTED INDENTATION TESTING
Load (P)
ht hcψ
Ac = f(hc)
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
12
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
DEPTH SENSING INDENTATION DESCRIBE MATERIALS BEHAVIOUR: ELASTIC TO PLASTIC DEFORMATION
Stress-Straincurves
Indentationcurves
Indentationprints
Plastic Elastic - PlasticElastic
F
h
F
h
F
h
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
13
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
QUASI-STATIC INSTRUMENTED INDENTATION TESTING
cA
PH
)( cc hfA
S
Phhc
thhdh
dPS
W.C. Oliver and G.M. PharrJ . Mater. Res., Vol. 19, No. 1, J an 2004
INPUT
)(3
metalsH
y i
i
s
s
EEE
111*
OUTPUT
Fitting of the unloading curve and first derivative at h=ht
(+ Correction for frame stiffness)
ε = 0.75 for a Berkovich indenter
Area function is obtained by independent measurements on fused silica reference sample
cA
SE
2*
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
14
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
NANO HARDNESS MAPSN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
15
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Stiffness is determined NOT from the unloading curve, but continuously from the ratio of the amplitude of the imposed force oscillation (F0) to the
amplitude of the resulting displacement oscillation (z0)
CONTINUOUS STIFFNESS MEASUREMENT (CSM): IN DEPTH H AND E VARIATION, VISCOELASTICITY
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
16
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
NANOINDENTATION WITH CSM
W. C. Oliver, G. M. Pharr, J. Mater. Res., Vol. 19, No. 1, Jan 2004
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
17
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
80 nm thin ALD coating TiO2-Al2O3 coating on silver substrate (Roma Tre).
CSM: ANALYSIS OF THIN COATINGS
Intrinsic hardness of the top layer
TEM, 120kV, 380.000x dual-layer coating
Pt
TiO2
Al2O3
Silver
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
18
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Tip rounding Surface roughness and
chemistry Thermal Drift Initial penetration depth Instrument compliance Indenter geometry Specimen preparation and
mounting Piling-up / sinking-in Substrate effect Indentation size effect Residual stress
FACTORS AFFECTING RESULTSN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
19
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
NANO INDENTATION: WHAT’S REALLY HAPPENED?
The correct understanding of microstructural effects during nanoindentation is not straightforward; How to separate real microstructural effects from
artifacts? How to identify the actual deformation/failure
mechanisms? Must validate nanoindentation measurements materials behavior during indentation would not
be considered with just continuum theory The solution relies in the coupled and
synergic use of high resolution microscopy techniques and indentation testing
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
20
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
21
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Evolution of characterization techniques and new potential of their synergic
uses
Dual-beam microscopy
LIME LAB: DUALBEAM (FEI) HELIOS 600 NANOLAB
early 2008
- Omnprobe- GIS (4 gases)- STEM- EDS (Oxford)
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
22
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
23
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
DUALBEAM (FEI)SEM Column: spatial resolution
0,69 nm @ 15 kVFIB Column: spatial resolution
5 nm @ 30 kV
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
24
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
HIGH RESOLUTION ELECTRON COLUMN 0,69 nm resolution, up to more that 1 million X
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
25
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
ION-SAMPLE INTERACTIONN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
26
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
PRINCIPAL FIB MODES:
Milling
Imaging
Deposition
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
27
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
FIB MODES: ION IMAGING
• Voltage contrast: insulators appear dark while grounded conductors are bright.
• Materials contrast: differences in yield of secondary particles due to the way energy is lost in the material.
• Crystallographic orientation contrast (channeling contrast): incident ions are channeled down between lattice planes of the specimen.
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
28
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
PRINCIPAL FIB MODES:
Milling
Imaging
Deposition
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
29
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
FIB MODES: ION MILLINGN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
30
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
PRINCIPAL FIB MODES:
Milling
Imaging
Deposition
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
31
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
FIB MODES: DEPOSITION (PT)N
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
32
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Possibility to reveal microstructure beneath the surface with very little or practically no artifacts
Accurately localize the region of interest(within few nanometers)
Excellent technique even on soft materials
Time to produce a TEM lamella (couple of hours)
EDS and Scanning Transmission Imaging within the DualBeam also available
USING A DUALBEAM TO CHARACTERIZE SAMPLES; WHAT IS NEW WITH RESPECT TO CONVENTIONAL CHARACTERIZATION ROUTE?
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
33
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
CROSS SECTIONSN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
34
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
TEM LAMELLA PREPARATIONN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
35
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
36
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Results of experimental activities and discussion
Introduction and motivation
Brief Description of the adopted
characterization methodology
Results and discussion Conclusions
DEPOSITION OF COATINGS
37
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Four different coatings are produced, by varying the applied bias voltage and the nature of the substrate.
R20 797 CERN type sputtering on QUARTZ
R20 796 CERN type sputtering on COPPER
R30 804 BIAS type sputtering (100V) on QUARTZ
R30 803 BIAS type sputtering (100V) on COPPER
NANOINDENTATION: HOW TO GET THE RIGHT NUMBERS?
38
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
1000 nm 500 nm
200 nm 100 nm
NANOINDENTATION: HOW TO GET THE RIGHT NUMBERS?
39
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
1000 nm 500 nm
200 nm 100 nm
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
NANOINDENTATION (CSM) ON NB THIN FILMS
500 nmSubstrate Influence on measured Hardness
Substrate effects!!
40
Hardness data are not affected by the substrate only for a penetration depth < t/10
NANOINDENTATION: SURFACE EFFECTS
41
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Inaccuracies on hardness and modulus at indentation depths lower than 30 nm, due to roughness and tip
rounding effects
Elastic modulus at 25 nm:93,2 ± 35,82 GPa
Elastic modulus at 100 nm:106,21 ± 13,35 GPa
NANOINDENTATION: DEFORMATION MECHANISMS
Pt deposition and FIB sectioning
500 nm
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
42
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Partial re-crystallization during plastic deformation;
Relative sliding of columnar grain
Direct measurement of piling-up
Analysis of deformation mechanisms
NANOINDENTATION: DEFORMATION MECHANISMS
200 nm
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
43
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Piling-up is still visible, but it is less pronounced
No more evidence of columns sliding and bending
Platic deformation is only given by dislocation nucleation and multiplication inside the grains.
NANOINDENTATION RESULTS SUMMARY
44
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Sample code Description NanoindentationStandard micro-
indentation
H (GPa) E (GPa)H (GPa)
Korsunsky model
796Nb on Cu BIAS
type3,10 ± 0,58 101,5 ± 23,61 2,51 ± 0,15
797Nb on Quartz
BIAS type1,63 ± 0,30 76,22 ± 48,99 1,75 ± 0,12
803Nb on CuCERN type
2,59 ± 0,35 108,68 ± 11,65 2,38 ± 0,15
804Nb on Quartz
CERN type2,19 ± 0,31 95,95 ± 26,31 2,01 ± 0.10
DEFORMATION MECHANISMS AT HIGH LOADS
45
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Strong pile-up at high indentation loads (> 1N)
Vickers 1 N
DEFORMATION MECHANISMS AT HIGH LOADS
46
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Very low plastic deformation of the substrate
Lateral plastic flow, with strong column bending
Complete re-crystallization due to plastic deformation at the top of piled-up material
MICRO-HARDNESS ON SOFT-ON-HARD SYSTEMS
47
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Fitting of models for extracting properties from MICRO-hardness testing is not straightforward in this case due to the observed deformation mechanisms;
COATINGS ON COPPER SUBSTRATE
BIASED (a-b)and UNBIASED
(CERN, c-d)
type coatings on COPPER substrate
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
48
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
COATINGS ON COPPER SUBSTRATEN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
49
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
BIASED (a-b)and UNBIASED
(CERN, c-d)
type coatings on QUARTZ substrate
NANOINDENTATION: OXIDE LAYER
50
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Niobium film load-depth curves
Load On Sample vs Displacement Into Surface
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 50 100
Displacement Into Surface (nm)
Load
On
Sam
ple (
mN)
0
0,005
0,01
0,015
0,02
0,025
0,03
0 5 10 15 20 25
Displacement Into Surface (nm)
Load
On
Sam
ple
(mN)
Niobium film load-depth curve
Niobium film: Detail of a load-depth curve
Indenter pop-in systematically observed at depth ~ 10 nm
TEM ANALYSIS OF THE OXIDE LAYER
768F BF 25000X film Nb
768F BF 380000X grain
boundary
768F BF 140000X grain
boundaries
768F BF 660000X oxide
layer
768F BF 140000X grain
boundaries
768F BF 660000X oxide
layer
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
51
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
The control of surface oxide layer can be very important in determining the functional performances of Nb coatings for superconducting applications
52INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization of niobium films obtained by MS and Bias-MS PVD
ResultsHalbritter, Journal Of Applied Physics 97, 083904 (April, 2005)
FIB-SEM MICROSTRUCTURAL ANALYSIS
An improper preparation of the copper substrate (usually electro-polishing + chemical polishing) dramatically decrease the interface and film quality, and the surface smoothness
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
53
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
CORRELATION TO SUPERCONDUCTING PERFORMANCES
54
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
A difference in terms of Tc is observed between biased and unbiased films on quartz;
This suggest a microstructural and morphological difference (density, grain size, lattice distortion, residual stress)
Should we expect the same differences in terms of Tc also for coatings on Copper?
DISCUSSION: WHAT ABOUT RESIDUAL STRESS?
55
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
A difference in residual stress is expected both in case of different substrate and in case of applied bias voltage: Residual stress can reduce the elastic strain to
failure, thus enhancing the possibility of defect formation (dislocations, delamination, micro-cracking and debonding of grains)
Residual stress arises from a lattice distortion, thus influencing the electron-phonon coupling constant and the superconducting performance.
CONCLUSIONS
Nano-mechanical testing can be a valuable procedure for the assessment of basic quality indicators for Nb films on either Copper or Quartz;
Careful analysis of the raw data coming from nanoindentation allows to find out several important information: Actual elastic modulus and hardness of the coatings, leading to more reliable
comparisons between samples; Presence of a thin oxide layer Surface and substrate effects Indirect evaluation of coating density
A correlation is found between surface micro-roughness, coating density, mechanical properties and superconducting performance;
The coupled use of HR microscopy techniques and hardness testing has been the key point of all research activities
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
56
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
FUTURE ACTIVITIES: FIB-DIC METHOD FOR MEASURING STRESS GRADIENTS IN COATINGS
57
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Lateral resolution: <1um; Depth resolution: <100 nm Semi-automated procedure
DIC
FEMDual Beam FIB/SEM
This is an example of a PVD Gold film on Silicon…
Stress gradient analysis in Niobium films is still an unexplored field…PLEASE SEND US SAMPLES!!!
THANK YOU FOR YOURTIME AND ATTENTION !
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
58
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
59
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Introduction and motivation
Brief Description of the adopted
characterization methodology
Results and discussion Conclusions
The starting point of the work here presented are the results published in a recent paper on Supercond. Sci. Technol. (21 (2008) 125026):
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
60
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
0.2
0.3
0.4
0.5
0.60.70.80.9
1
1 10
DMA
Nanoindentation
Lo
ss F
act
or
(-)
Frequency (Hz)
3
4
5
6
789
10
1 10
DMA
Nanoindentation
Sto
rag
e M
od
ulu
s (M
Pa)
Frequency (Hz)
Dynamic characterization of polymers in the time and frequency domains using a flat punch
Highly plasticized polyvinylchloride,the complex modulus at 22 oC
Supeconducting properties of MS-PVD Nb films are significantly affected by Grain size surface roughness coating density interfaces integrity
A completely different behaviour is expected for the BIASED Nb coating deposited on Quartz substrate
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
62
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
M. S
ebastia
ni: A
pp
licatio
ns o
f nanoin
denta
tion
te
chniq
ues to
non-h
om
ogeneous m
ate
rials a
nd
structu
res
63
MTS N
ano E
vent
Rom
a T
RE, A
pril 3
/04
/20
08
Surface Layers - Thin Film Effects
Film
Substrate
Hardness
Hfilm
Hsubstrate
Indentation Depth/Film Thickness
1 2
Soft film on hard substrate
Substrate
Film Hardness
Hfilm
Hsubstrate
Indentation Depth/Film Thickness
1
Hard film on soft substrate
Perfect pyramid or cone:
(C0 constant, 24.5 for Vickers)
Perfect tip shape do not exist in the reality (tip blunting)
Perfect tip
Real tip
Tip Calibration
AP AND TIP CALIBRATION
20p hCA
h
Ap
...hChChChCA 4
1
32
1
212
0p
Nan
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
64
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
HARD INCLUSION IN A SOFT METALN
an
o-m
ech
anica
l an
d m
icrostru
ctura
l ch
ara
cteriza
tion o
f MS-P
VD
Nb th
in fi
lms
65
Marco
Sebastia
ni,
Leg
naro
Natio
nal La
bora
torie
s Octo
ber 4
20
10
Top Related