sebastiani - nano-mechanical and microstructural characterization of ms-pvd nb thin films

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

www.lime.uniroma3.itN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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??

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

INTRODUCTION

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Supercond. Sci. Technol. (21 (2008) 125026)

GAP OF KNOWLEDGE

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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.

AIM OF THE WORK

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

Introduction and motivation

Brief Description of the adopted

characterization methodology

Results and discussion Conclusions

Evolution of characterization techniques and new potential of their synergic

Nano-Indentatio

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Sebastia

nal La

s Octo

icrostru

cteriza

tion o

f MS-P

HARDNESS – SCALE OF INDENTATION

Macro-hardness

Micro-hardness

Nano-hardness

10 N 10 mN Load

ROMA TRE NANOHARDNESS TESTER

Berkovich tip

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

early 2008- CSM option- Lateral force measurement- Nano- positioninng stage

INSTRUMENTED INDENTATION TESTING

Load (P)

ht hcψ

Ac = f(hc)

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

DEPTH SENSING INDENTATION DESCRIBE MATERIALS BEHAVIOUR: ELASTIC TO PLASTIC DEFORMATION

Stress-Straincurves

Indentationcurves

Indentationprints

Plastic Elastic - PlasticElastic

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

QUASI-STATIC INSTRUMENTED INDENTATION TESTING

)( cc hfA

W.C. Oliver and G.M. PharrJ . Mater. Res., Vol. 19, No. 1, J an 2004

metalsH

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

NANO HARDNESS MAPSN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

NANOINDENTATION WITH CSM

W. C. Oliver, G. M. Pharr, J. Mater. Res., Vol. 19, No. 1, Jan 2004

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

Silver

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Evolution of characterization techniques and new potential of their synergic

Dual-beam microscopy

LIME LAB: DUALBEAM (FEI) HELIOS 600 NANOLAB

early 2008

- Omnprobe- GIS (4 gases)- STEM- EDS (Oxford)

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

DUALBEAM (FEI)SEM Column: spatial resolution

0,69 nm @ 15 kVFIB Column: spatial resolution

5 nm @ 30 kV

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

HIGH RESOLUTION ELECTRON COLUMN 0,69 nm resolution, up to more that 1 million X

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

ION-SAMPLE INTERACTIONN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

PRINCIPAL FIB MODES:

Milling

Imaging

Deposition

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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.

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Milling

Imaging

Deposition

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

FIB MODES: ION MILLINGN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Milling

Imaging

Deposition

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

FIB MODES: DEPOSITION (PT)N

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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?

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

CROSS SECTIONSN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

TEM LAMELLA PREPARATIONN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Results of experimental activities and discussion

DEPOSITION OF COATINGS

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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?

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

1000 nm 500 nm

200 nm 100 nm

NANOINDENTATION: HOW TO GET THE RIGHT NUMBERS?

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

1000 nm 500 nm

200 nm 100 nm

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

NANOINDENTATION (CSM) ON NB THIN FILMS

500 nmSubstrate Influence on measured Hardness

Substrate effects!!

Hardness data are not affected by the substrate only for a penetration depth < t/10

NANOINDENTATION: SURFACE EFFECTS

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Strong pile-up at high indentation loads (> 1N)

Vickers 1 N

DEFORMATION MECHANISMS AT HIGH LOADS

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

COATINGS ON COPPER SUBSTRATEN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

BIASED (a-b)and UNBIASED

(CERN, c-d)

type coatings on QUARTZ substrate

NANOINDENTATION: OXIDE LAYER

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Niobium film load-depth curves

Load On Sample vs Displacement Into Surface

0 50 100

Displacement Into Surface (nm)

0 5 10 15 20 25

Displacement Into Surface (nm)

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

boundaries

768F BF 660000X oxide

boundaries

768F BF 660000X oxide

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

CORRELATION TO SUPERCONDUCTING PERFORMANCES

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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?

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

FUTURE ACTIVITIES: FIB-DIC METHOD FOR MEASURING STRESS GRADIENTS IN COATINGS

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

Lateral resolution: <1um; Depth resolution: <100 nm Semi-automated procedure

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 !

marco.sebastiani@stm.uniroma3.it

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

The starting point of the work here presented are the results published in a recent paper on Supercond. Sci. Technol. (21 (2008) 125026):

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

0.60.70.80.9

Nanoindentation

Frequency (Hz)

Nanoindentation

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

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

ebastia

licatio

f nanoin

ues to

ogeneous m

rials a

structu

pril 3

Surface Layers - Thin Film Effects

Substrate

Hardness

Hsubstrate

Indentation Depth/Film Thickness

Soft film on hard substrate

Substrate

Film Hardness

Hsubstrate

Indentation Depth/Film Thickness

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

...hChChChCA 4

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

HARD INCLUSION IN A SOFT METALN

icrostru

cteriza

tion o

f MS-P

Sebastia

nal La

s Octo

sebastiani - nano-mechanical and microstructural characterization of ms-pvd nb thin films

Technology

reazioni chimiche: stechiometria sebastiani,soldati,esposito

mechanical and microstructural development of …€¦ ·...

microstructural, mechanical and tribological...

iso-line - cf-tools.de · hta revêtement pvd pvd...

xister - cultural media & behavioural marketing - 2012 -...

revestimento pvd

evicore pvd imaging guidelines - v2 · 8/11/2014 ·...

pvd coatings

tema.pdf pvd

cloverfield online strategy by carlo sebastiani

costruzioni metalliche - angelelli maffei sebastiani

sample copy...bg pvd brushed gold pvd oro cepillado pvd or...

high resolution morphological and mechanical...

sebastiani - socialismo 1946-1951

jorge luís sebastiani - repositorio.ufsm.br

ugradna ploca za kuvanje pvd 644 pvd 742

m9000 -...

catalogo pvd

canon anelva pvd equipments treatment resin plasma...

propuesta pvd