Nano Indentation Lecture2

Do Kyung Kim Department of Materials Science and Engineering KAIST, Korea Nanoindentation Lecture 2 Case Study

Applications of nanoindentation
Mechanical characterization of nanostructures
Pressure-induced phase transformation
Thin film and MEMS structure – mechanical properties
Biomechanics
Newly Developed Technique

Mechanical Characterization of Nanostructures

Carbon Nanotube (1)
Vertically aligned carbon nanotubes were prepared using PECVD method with different nickel catalyst thickness.
The nanoindentation on a VACNT forest consecutively bends nanotubes during the penetration of the indenter.
Sample A Sample B Sample C Gleason, J Mech Phys Solids, 2003

Carbon Nanotube (2)
The resistance of a VACNT forest to penetration is due to successive bending of nanotubes as the indenter encounters nanotubes
Superposition of interaction between the indenter and nanotubes encountered by the indenter during nanoindentation gives the total penetration resistance.
Gleason, J Mech Phys Solids, 2003

Carbon Nanotube (2)
Average f-p curve for the three samples from experiements
Sample C (high density, small length) Sample A, B (Same density) Sample A (Larger diameter and smaller length)
Gleason, J Mech Phys Solids, 2003

Silver Nanowire (1)
Silver nanowire-not single crystal but twinned-prepared from two silver solutions (AgNO3 and NaOH) and adhered onto glass slide.
Nanoindentation and imaging with same Berkovich indenter.
Penetration depth as low as 15 nm. (30 % of diameter)
Caswell, Nano Letters, 2003

Silver Nanowire (2)
Hardness 0.87 GPa / Elastic modulus 88 GPa
In good agreement with the nanoindentation value of bulk single crystal, 2 times higher than macroscale indentation results (indentation size effect)
This approach permits the direct machining of nanowires.
Caswell, Nano Letters, 2003

ZnO and SnO2 nanobelt (1)
The nanobelts were synthesized by thermal evaporation of oxide powder.
Indentation with maximum 300  N with loading rate 10  N/s
Wang, APL, 2003

ZnO and SnO2 nanobelt (2)
ZnO is a little softer than bulk single crystal.
The crack propagates along [101] and cleavage surface is (010).
Wang, APL, 2003

Pressure-induced Phase Transformation

Silicon (1)
Single crystal silicon undergoes phase transformation during indentation
A sudden displacement discontinuity referred to as a pop-in
Upon unloading, pop-out or kink pop-out happen, resulting from a sudden material expansion
Gogotsi, J Mater Res, 2004

Silicon (2)
The average pop-in pressure is determined from pure elastic loading assumption.

Silicon (3)
Single and multiple pop-in events occurred during indentation
These events could be due to either subsurface cracking, squeezing out of ductile materials or sudden dislocation burtst
1 mN/s 5 mN/s Gogotsi, J Mater Res, 2004

Silicon (4)
A great amount of a-Si, Si-III, or Si-XII is at deeper rather than shallower depths for a number of unloading conditions.
The results from different wavelength spectrum show a-Si, Si-III, or Si-XII exist below the surface.
Pop-in, out  Si-III or Si-XII and No pop-in, out  a-Si

Germanium (1)
Nanoindentation experiments were performed using Berkovich and cube-corner indenters
The unloading pop-out or elbow phenomena was not observed in loading curve.
A number of displacement discontinuities in the loading curve are caused by discontinuous crack extension and chipping.
Pharr, APL, 2005

Germanium (2)
SEM observation of the cube corner hardness impressions revealed a thin layer of extruded material.
The micro-Raman spectra for cube-corner indentation exhibits distinct narrow Ge-IV and a-Ge peaks.
Ge-IV phased vanishes within 20 hours of removing pressure.
Pharr, APL, 2005

Thin Film and MEMS Structure – Mechanical Properties

MEMS structure (1)
Silicon nanobeam fabricated by micromachining process
Load applied by indentation loading machine
Si strength-17.6 GPa (bulk single crystal strength 6 GPa)
Similar elastic modulus
Li, Ultramicroscopy, 2003

MEMS structure (2)
SiO2 microbeam fabrication by micromachining process
SiO2 strength 68 Gpa (18.5  m sample) / 2.5 Gpa (58.5  m sample)
Lee, J Kor Ceram Soc, 2003

Thin films – Al (1)
Aluminum single crystal (111) showing pop-in behavior
The maximum critical load 22  N  a mean pressure 14.7 GPa which is equivalent to a simplified estimate of the theoritical shear stress.
Dislocation is responsible for pop-in events.
Moris Jr, J Mater Res, 2004

Thin films – Al (2)
In situ nanoindentation
Approach  Contact  Plastic deformation  Extensive dislocation activity
Moris Jr, J Mater Res, 2004

Thin films – Al (3) Before indentation After indentation with same direction After indentation with tilted direction (dislocation in entire grain) Moris Jr, J Mater Res, 2004

Residual stress (1)
Residual stress from
non-uniform cooling down from the processing temperature
deposition of a surface coating or a thin film on a substrate
Equal biaxial state of residual stress (tensile or compressive)
Suresh, Acta Mater, 1998

Residual stress (2)
Tensile
Compressive

Residual stress (3)
Implementation with ref. sample

Superlattice (1)
Nanscale multilayered coating
W/ZrN nanolayer
Superlattice period: 2.1 nm
Annealed at 1000  C for 1hr
AlN/VN nanolayer
Epitaxial stabilization of B1-AlN
Transformation to wurtzite
Scott, MRS bulletin, 2003

Superlattice (2)
Nanoindentation TiN/TiB2 superlattice
Scott, MRS bulletin, 2003

Biomechanics

Dental hard tissue (1) Anisotropic structure of enamel Swain, J Mater Res, 2006

Dental hard tissue (1)
Nanoindentation experiments on enamel with different orientation and indenter radius
Parallel to enamel rods, the hardness and modulus are 3.9 Gpa and 87.5 GPa, respectively , whereas perpendicular to enamel rods, they are 3.3 GPa and 72.2 GPa.

Dental hard tissue (3)
The bacterial demineralization in enamel known as caries is simply detected through the changes in its mechanical properties.

Dental hard tissue (4) Weihs, Archives of Oral Biology, 2002 Nanoindentation mapping of enamel tooth structure Lingual Buccal Pulp Dentin Hardness (GPa) 2.5 3 3.5 4.0 4.5 5 5.5 6 Lingual Buccal Pulp Dentin Elastic Modulus (GPa) 110 100 90 80 70 60 50 120

Human bone (1)
Human Femur – cortical and trabecula bone lamellae
Goldstein, J Biomech, 1999

Human bone (2)
The mean elastic modulus was found to be significantly influenced by the type of lamella and by donor.
Hardness followed a similar distribution as elastic modulus among types of lamellae and donor.
Goldstein, J Biomech, 1999

Biocomposite (1)
Hydroxyapatite (HA) + polymethylmethacrylate (PMMA) + co-polymer coupling agent
In vitro interfacial mechanics of HA and PMMA cross section of the composite
Microscopic analysis
Indentation analysis (load-displacement curve)  more comprehensive local analysis
In vitro testing – a reduction of bulk bending, local elastic modulus, local hardness with increase of immersion time
The effect of coupling agent  improvement of the interfacial mechanics
Marcolongo, IEEE Bioeng, 2004

Biocomposite (2)
Human bone
45-60% mineral: HA
20-30% matrix: collagen
10-20% water

Biocomposite (3)
To determine the local mechanical properties of a bioactive composite a function of immersion period in simulated body fluid (SBF)  in vitro testing

Biocomposite (4)
The “in vitro” local mechanical properties of the bioactive composite as a function of surface bioactivity

Newly Developed Technique

Cross-section of indentation damage(1) Indentation Pt Fast mill Tilt Markers Slow mill Lift-off Bradby, 2004
Focused ion beam TEM sample preparation

Cross-section of indentation damage(2) Fast unloading Slow unloading Slip line Misc. defect Extended defect Bradby, 2004 Silicon

Cross-section of indentation damage(3) GaAs InP Bradby, 2004

Cross-section of indentation damage(4) GaN ZnO Bradby, 2004

In-situ nanoindentation in SEM (1) Utke, 2006

In-situ nanoindentation in SEM (2)
Vitreloy 105 (Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 )
Partial correlation between shear band formation and displacement burst in P-h curve. Utke, 2006

In-situ nanoindentation in SEM (3)
FEB deposited reference pattern for in situ measure of contact area
Utke, 2006

In-situ nanoindentation in SEM (4) Silicon pillar Median crack Basal crack Buckling Utke, 2006

In-situ nanoindentation in TEM (1) Minor, 2002

In-situ nanoindentation in TEM (2) Minor, 2002

In-situ nanoindentation in TEM (3) Before After Minor, 2002

Concluding remarks
Broad applications of Nanoindentation to investigate the mechanical properties!!!

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