October 24, 2016 1

www.bruker.com

NanoForce

-short note -

Ilja Hermann

October 24, 2016 2

NanoForce

System overview

• Electromagnetic actuator (indentation loads between 0.2 uN and 45 mN) • Three-plate capacitor (indentation depth up to 40 um)• Load control • Depth- and strain-rate control by S/W feedback control• Berkovich tip is included; misc. different indenter geometries optional; easy switch • In-line microscope with coaxial turret optics and AFM are standard• Automatic multi-specimen handling (magnetic, vacuum, mech. clamp mounting)

Coaxial optical lenses and AFM

Thermal/Acoustic/Seismic hood

Internal (3-plate) capacitance sensor housing

Microscope for inspection pre- and pre- and post-test

Actuator housing

Quantitative property assessment: HIT, EIT, E’ , E”, Y, KIC, σRep(εRep), FCrit., topography

Optional vacuum chuck

Specimen tray

October 24, 2016 3

NanoForce

System data sheet

Basic configuration with imaging options

Scratch option

October 24, 2016 4

Typcial Nanoindentation test

AFM & Optical View (post IMG of surface with 9 indents at different surface locations)

Force-Displacement curves(Dynamic indentations at 9 different surface positions)

NanoForce

1. Test positioning

2. Applying the test method (running indent-loading profile and analysis)

3. Post inspection of tested surface area

1.7mm

1.5 um

Indentations

Cube corner into Si (100)

Berkovich into HPFS

How small the testing object can be (NanoForce tip has to hit the spot)?

Even after subsequently adding 9 more indents, all tests remain <0.5 um away from target position

Tim

eli

ne

NanoForce

IndentAFM

10-timesExperiment:

After indent #1 After indent #10

Target

=> Nanoforce can perform NI experiments on specimen under 1 um lateral size

ftp://tmtftp.bruker-nano.com/tmt/outgoing/NanoForce/Nano-Dart.m4vVideo:

NanoForce

Instrument calibration

October 24, 20167

Hardness and Young’s Modulus on SiO2NanoForce results at different surface positions

Typical results for dynamic indentation:

NanoForce

Force-Displacement curve

(corrected raw-data)

F/S^2

Hardness

Modulus

October 24, 2016 8

Quasi-static Indentation –hardness and- modulus on reference materials

HPFS

BK7

NanoForce

Typical Hardness- and Modulus-measurements on homogenous materials used

for instrument verification.

HPFS

BK7

NanoForce

Thin film applications

October 24, 2016 10

NanoForce

Dynamic measurements of thermal-SiO2 film on Silicon

Strain-rate controlled indentation with Berkovich tip and

superimposed 2 nm harmonic excitation amplitude @ 120 Hz

on various thickness on Si (100) on substrate:

50 nm

100 nm

300 nm

Bulk

Bulk SiO2:~72 GPa

Bulk Si: ~164 GPa

October 24, 2016 11

NanoForce

Brittle material characterization

October 24, 2016 12

Fracture toughness

Nano-indentation results

Method inputs:

E…Young’s modulus

H…hardness

P…test load

a, c, l….distances from imageBerkovich [2]:

Cube Corner [1]:

Step 2: Produce a series of indentations at different loads and surface locations

Step 3: Image indents to find critical load for fully developed set of lead corner radial cracks

Step 4: Calculate Fracture toughness :

Step 1: Measure Hardness and Young’s modulus of the specimen

[1] D. S. Harding, W. C. Oliver and G. M. Pharr: Mat. Res. Soc. Symp. Proc., 356, 1995, 663.

[2] R. Dukino and M.V. Swain, J. Am. Ceram. Soc. 75 12, 1992, 3299

October 24, 2016 13

NanoForce

Characterization of metallic single crystals

October 24, 2016 14

NanoForce

• Initial elastic-plastic transition can be observed at ~20uN

• Perfect elastic partial unloading cycles (no hysteresis)

• Pop-ins appear associated to the beginning / end of a partial unloading cycle

Quasi-static indentation with multiple-partial unloading

Modified Berkovich tip on Aluminum (110) single crystal

Fkrit

October 24, 2016 15

NanoForce

Dynamic indentation on single crystals:

Cu (110)Cu (111)

• The (111) orientation appears stiffer than the (110) orientation

• The (111) orientation exhibits pop-in events at approx. 10 uN load

Fkrit

Cube Corner tip on Copper (110) and (111) orientations

October 24, 2016 16

NanoForce

Indentation Creep

October 24, 2016 17

NanoForce

• Indentation Creep found to be CIT~6%

• Most significant contributor to depth-increase during peak-load-hold time are

pop-in events (Plastic flow/ dislocation mobility)

Quasi-static indentation with multiple-partial unloading and CREEP

Cube corner on Aluminum (110) single crystal

OM AFM

CREEP @ Pmax

Pop-in @ constant load

October 24, 2016 18

NanoForce

(Soft) Polymers

October 24, 2016 19

NanoForce

(soft) Polymers

Quasi-static indentation on PDMS with cube corner tip(…very sharp on very soft…)

EIT=(5.4+-0.2) Mpa

HIT=(1.07+-0.08) Mpa

EIT=(2.55+-0.53) Mpa

HIT=(0.36+-0.02) Mpa

CIT=(52+-9) %

CIT=(33.7+-2.6) %

• Repeatable raw-data due to precise load-control below 10 uN• Both PDMS-blends clearly distiguished at hand of raw-curves (F(h), h(t))• Resultant YOUNG’s modulus is in line with expectations (3.5 Mpa & 2.5 MPa resp. for PeakForce QNM)• Indentation creep exceeds 30%

October 24, 2016 20

NanoForce

Adhesion

October 24, 2016 21

NanoForce

Adhesion

Quasi-static indentation on PDMS with 50 um conical tip

Obtain quantitative data : • DMT modulus , starting @ ~1 Mpa• Adhesion • Energy dissipation• Surface deformation

Adhesionrindenter PRdEP +=3

3

4

Tip-stiction forces was measured @ approach (and pull-off) down to 2.5 um radius

Contact model with stiction (DMT)

Nano-Indenter gives

insights into new more

complex contact physics:

R=50um

R=5 um

R=2.5 um

October 24, 2016 22

NanoForce

Scratch

NanoForce

Micro-Scratch

• 5x scratch into AL(110) Length 200 um length, lateral strain rate 0.1 Hz , Conical R=5 um, • 50x optical magnification, stitched

progressive load 0.5-10 mN

constant load 10 mN

Repeatability:

NanoForce

Constant load Nano-Scratch – 300 nm SiO2 on Si with Conical 2.5 um

• Pairs of constant load scratch series (1, 3, 5, 7, 10) mN, Length 20 um, 10mN; Strain rate 0.1 Hz

_P130

topography (NanoLens) 1-D profile through scratch series

NanoForce

Nano-Scratch

1x progressive load scratch; 0.5-10 mN; Length 20 um length, Strain rate 0.1 Hz; Conical R=5 um

25 nm ITO on PET

30 nm SiO2 on PET

NanoForce

Nano-Scratch

2x progressive load scratch; 0.5-50 mN; Length 20 um length, Strain rate 0.1 Hz; Conical R=5 um

24 nm brittle film on Si

Fcrit~44mN

Instrumented scratch data:

Longitudinal Profiling @ load

NanoForce

Progressive Zig-Zag-Micro-Scratch – 300 nm SiO2 on Si with Conical 2.5 um

Fcrit~25 mN

Stage Motion Trajectory

1x progressive load ZigZag scratch; Length 50 um, 25 cycles , Pitch 1 um , 1-50mN; lateral strain rate 1 Hz

_P130

NanoForce

Progressive Zig-Zag-Micro-Scratch – 300 nm SiO2 on Si with Conical 2.5 um

Failure event identification by tip-profiling

• 1x progressive load ZigZag scratch; Length 50 um, 25 cycles , Pitch 1 um , 1-30mN; lateral Strain rate 1 Hz

• Transversal post-profiling with indenter tip @ average profiling loads ca. 2 uN

_P130

Cleaned from debris

ZigZag-Trajectory

Straight Trajectory

Topography

Profiling load stability

Critical load determination e.g. by counting integer # of traces ; uncertainty is

the scratch length

Note: Regular progressive scratch shows no failure while ZigZag

scratch promotes this @ same range of load variation

NanoForce

Progressive Zig-Zag-Nano-Scratch – 300 nm SiO2 on Si with Conical 2.5 um

Catastrophic failure of 300 nm coating can be induced via ZigZag scratch

when a regular progressive load scratch would not fail the coating system

1x progressive load ZigZag scratch; Length 10 um, 25 cycles , Pitch 1 um , 1-30mN; Strain rate 1 Hz

_P130

Topography

Critical load determination by counting integer # of traces ; uncertainty is the scratch length

Error Signal

October 24, 2016 30

NanoForce

Other misc. applications

Imaging: AFM topography of a Berkovich tip

Tip radius ~40nm

NanoForce

Direct measurement:

October 24, 2016 32

NanoForce

Precision of head mount and Indenter tip mounting

Cube Corner tip => Berkovich tip

Berkovich Tip => Conical tip

• mod. Berkovich

• Cube Corner

• Vickers

• Conical R=Var

• Flat Punch R=Var

• …

NanoForce tip shape options:

Requires remove/reinstall tip

Experiment: Measure remaining pos. accuracy after tip change

Quiz:

What if re-cal is skipped?:

Pos error ~7 um

Pos error ~5 um

Answer:

No big problem: pos accuracy remain better 10 um !(…and is this is not enough – best accuracy is just s fe clicks away (no new indent required)

and re-calibrate inline offset

October 24, 2016 33

NanoForce

Hertzian contact

i

Experiment

r

HertzModelS

Fh

RE

Fh −=

=

32

,

4

3

With:• Tip radius R from AFM (calculations with radius as function of depth (R(h))• Best Fit for 3 reference materials (Fused Silica, Sapphire 0001 and Si 100)

Extraction of Load-Frame stiffness from Hertzian contact modeling

Overall system stiffness: ~2.5 N/um

(good agreement with 2.2 N/um from elastic-

plastic indentation (F/S^2))

October 24, 2016 34

NanoForce

Surface Roughness measurement

Fused Silica, Contact, 256pts/ln

October 24, 2016 35

NanoForce

Optical Microscope

• FOV All pixels

• Resolution ~500nm opt; ~1.7 nm afm scanner

• >3000x total magnification + digital zoom

• Bright-field illumination;

• Optional: Extra objectives & Dark-field

5x2.5x

8x

10x

20x

AFM

optional

Standard

DF

BF

Silicon or smooth, reflective

surfaces in Bright-field…

Skin or rough, absorbing surfaces:

Dark-field…

Vs. dark-field…

2.5x

2.5x50x

October 24, 2016 36

[Diagonal] = mm

28544.1

d

FHV =

[Applied load] = kgf

Concept: 1. Apply load

2. Analysis of residual imprint after load removal

Direct method…. -difficult to co-relate to physical properties

-No elastic properties

+

(static load) (OM image)

Ca

lcu

late

nu

mb

er

Static Apply static concept with NanoForce

NanoForce

Hardness measurement with Sharp (cone/pyramid) - the traditional way

2. Direct measurement of actual- or projected contact area Ac by AFM…3. Calculate Hardness4. Convert to other hardness scales.

1. Apply loading profile