Paul Ahern - Time of Flight Secondary Ion Mass Spectroscopy [ToF-SIMS] theory & practice
Applications of XPS, AES and ToF-SIMS for Solving Problems in Materials...
Transcript of Applications of XPS, AES and ToF-SIMS for Solving Problems in Materials...
The Surface Analysis Laboratory
Applications of XPS, AES and ToF-SIMS for Solving Problems in Materials Research
John F Watts
Surrey Materials Institute &
Faculty of Engineering and Physical SciencesSI-Ontario
University of Toronto20 March 2008
The Surface Analysis Laboratory
University of Surrey
The Surface Analysis Laboratory
Surface AnalysisX-Ray Photoelectron Spectroscopy (XPS)
Auger Electron Spectroscopy (AES)
Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)
The Surface Analysis Laboratory
Handling Contamination
0
20000
40000
60000
80000
020040060080010001200
Cou
nts
/ s
Binding Energy (eV)
C O Al Si
17.0 58.2 24.8 0.0
0
10000
20000
30000
40000
020040060080010001200
Cou
nts
/ s
Binding Energy (eV)
C O Al Si
37.4 40.2 16.1 6.3
Clean aluminium foil (LHS) low adventitious carbon concentration, following handling by operative (hand cream user) concentration of carbon increases and significant concentration of silicon from silicone oils in hand cream (confirmed by ToF-SIMS).
The Surface Analysis Laboratory
Forensic Analysis
Canned beer is provided with a dense head by carbon dioxide contained in plastic “widget”
Early version were three part precision mouldings, but there was a desire to replace this with a single part “top hat” component heat sealed to the bottom of the container
The Surface Analysis Laboratory
XPS Survey Spectra
Nylon Nylon
C1s
O1s
N1s
Epoxy Lacquer Epoxy Lacquer
400 μm XPS
2 mm
Internal can surface Widget bonding surface
The Surface Analysis Laboratory
Photocured Adhesive
• LuxtrakTM photocured resin based on methacrylate type monomers
•Planned use in microelectronics industry
•Surface mounting of components on alumina
•Fails “pressure cooker” test i.e. adhesion in hot water
•Investigate failure surfaces by XPS after aqueous exposure
O O O
Resin Component
Reactive Diluent
The Surface Analysis Laboratory
C1s Spectra of Failure Surfaces
A M Taylor, C H McLean, M Charlton, J F Watts, Surf Interf Anal, 23, 342, (1995)
d = 1nm
The Surface Analysis Laboratory
Molecular Dynamics
Computer chemistry visualisation of reactive diluent at interface
XPS shows the overlayer on substrate side of failure to be about 1 nm of reactive diluent
The Surface Analysis Laboratory
Reformulated Resin
Reformulated resinwithout reactivediluent has betterdurability
Note π → π* on both interfacial failure surfaces
The Surface Analysis Laboratory
The Problem Faced by the Analyst
ARXPS d ~10nm
X-ray spectroscopies d ~200nm
RBS d ~1μm
d
Interface Region
Substrate
Adhesive or Coating10’s μm - mm
100’s μm - mm
The Surface Analysis Laboratory
The Buried Interface
Obtaining analytical information from intact interfaces is very difficult.
Carrying out in-situexperiments within the spectrometer can be useful but only rarely is the interphase chemistry exposed in this manner
J F Watts, Surf Interf Anal, 12, 497-503, (1988)
The Surface Analysis Laboratory
TEM/PEELS Cross-Sections
A J Kinloch, M Little, J F Watts, Acta Materialia, 48, 4543, (2000)
PAA treated joint PAA + primer joint
abrupt interface diffuse interphase
The Surface Analysis Laboratory
Oxide Stripping + Depth Profiling
Chemical removal of metal substrate, depth profiling of oxide in situ by ion sputtering. Interphase can then be analysed directly
J F Watts, J E Castle, J Mat Sci, 18, 2987, (1983)
The Surface Analysis Laboratory
Interface Chemistry
Fe(II)Fe(II) satellite
Iron 2p3/2 spectrum showing Fe(II) component at interface. Bulk oxide is entirely Fe(III).
The Surface Analysis Laboratory
Ultra Low Angle Microtomy
Angle Sectioning Block
12 x 12 x 7 mm3
+ 25 μm = 0.03O
+ 50 μm = 0.07O
+ 100 μm = 0.15O
+ 200 μm = 0.33O
Microtome Knife
Angled Sectioning Block
Polypropylene Block
The Surface Analysis Laboratory
ULAM Geometry
ULAM taper angle/oXPS spot size/μm 0.03 0.33 2.0
100 60 600 3500
15 13 100 500
Depth Resolution ULAM/nmCoating
Small area XPS analysis mode (100 μm)
Substrateθ
S J Hinder, C Lowe, J T Maxted, J F Watts, J Mater Sci, 40, 285, (2005)
Depth resolution attainable depends on the taper angle and the size of the analytical probe. In small area XPS in the range 15 -500 μm, for ToF-SIMS < 1 μm
The Surface Analysis Laboratory
XPS Line Scan Along Taper
0
2
4
6
8
10
12
14
16
18
20
0 0.013 0.026 0.039 0.052 0.065 0.078 0.091 0.104 0.117 0.13 0.143 0.156 0.169
Depth / um
Ato
mic
%
0
0.5
1
1.5
2
2.5
3
3.5
4
FluorineNitrogen
PVdF Polyurethane
X-ray Spot = 15μm
Step Size = 18 μm
13nmF: ΔZ = 50 nm
N: ΔZ = 27 nm
PVdF Topcoat on Polyurethane Primer
The Surface Analysis Laboratory
ToF-SIMS of ULAM Section
d)
b)a)
c)
1
3
2
+ve SIMS -ve SIMS
Polyurethane ions
PVdF ions
(a) m/z = 149: C8H5O3+
(b) m./z = 26: CN-
(c) m/z = 59: C3H4F+
(d) m/z = 19: F-
FoV is 500 μm
500 μm250 nm
S J Hinder, C Lowe, J T Maxted, J F Watts, Surf Interf Anal, 36, 1575, (2005)
The Surface Analysis Laboratory
ToF-SIMS Anions from Images
0
5 00
10 00
15 00
20 00
25 00
30 00
35 00
0 20 40 6 0 80 10 0 1 20 14 0 160 1 80 20 0m /z
Cou
nts
a)25
41-4249
66
100
121
0
1 5 0 0
3 0 0 0
4 5 0 0
6 0 0 0
7 5 0 0
9 0 0 0
1 0 5 0 0
1 2 0 0 0
1 3 5 0 0
1 5 0 0 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0m /z
Cou
nts
c) 19
49
39
85
Point 2: Bulk Polyurethane
Point 1: Bulk PVdF
c)
1
3
2
The Surface Analysis Laboratory
ToF-SIMS at Interface
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
1 2 0 0
1 4 0 0
0 2 0 4 0 6 0 80 1 00 1 2 0 1 4 0 1 6 0 1 8 0 20 0m /z
Cou
nts
b)19
31
55 71
87
85
121185141
Point 3: PU and PVdF at Interfacec)
1
3
2
PCA on Positive Spectra from Interfacial Region to Identify Those that are not Characteristic of PVdF or PU
Negative ToF-SIMS
The Surface Analysis Laboratory
Minor Additive
0
300
600
900
1200
1500
1800
2100
2400
2700
3000
30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
m/z
Cou
nts
31
55
71
85
185
41
A negative ion ToF-SIMS mass spectra of the pure acrylic co-resin component of the PVdF topcoat formulation in the mass range 30-200m/z.
x10
The Surface Analysis Laboratory
ToF-SIMS Images of Acrylic Ionsa) b)
e) f)
d)c)
Negative Ion Mass
Selected Images
(a) m/z = 31: CH3O-
(b) m/z = 55: C3H3O-
(c) m/z = 71: C3H3O2-
(d) m/z = 85: C4H5O2-
(e) m/z = 87: C4H7O2-
(f) m/z = 141: C9H13O4-
The Surface Analysis Laboratory
The Thin Film Approach
d
Interface Region
Substrate
Adhesive or Coating10’s μm - mm
100’s μm - mm
thin (< 2 nm film on substrate)
select sample from the plateau region of the adsorption isotherm
The Surface Analysis Laboratory
Organosilane Adhesion Promoters
Molecular Dynamics Models of:(a) Epoxy
(b) Amino
(c) Vinyl
The Surface Analysis Laboratory
Aluminium Pretreatment for Structural Adhesive Bonding
0.0
0.5
1.0
1.5
2.0
2.5
0 20 40 60 80 100 120 140 160 180Exposure time (hrs)
Frac
ture
ene
rgy
(kJm
-2)
1 hr hydration + silaneOptimised silane pre-treatmentGrit-blasted onlyCAA pre-treatmentPAA pre-treatment
The Surface Analysis Laboratory
High Resolution ToF-SIMS
The intense SiOAl+
peak is indicative of a
covalent bond between
the aluminium oxide
and the organosilane
adhesion promoter
The Surface Analysis Laboratory
Specific Interactions
SiHO
OH
O
(CH2)3 O CH2 CH CH2
OH
Al
O H
SiHO
OH
O
(CH2)3 O CH2 CH CH2
O
Al
The Surface Analysis Laboratory
Wedge Test Failure Surfaces
Epoxy Adhesive + 1% GPS: XPS Images
Opticalmirror images
C1s Al2p Si2p
The Surface Analysis Laboratory
Single Fibre Pull-Out Test: Cradle to Grave ToF-SIMS
• Single fibre mounted in carrier syringe needle• Specially designed cradle used to hold sample• Fibre observed using optical microscope• Fibre presented to spectrometer for ToF-SIMS analysis pre-
embedding into resin system• Fibre embedded and SFPO test conducted• ToF-SIMS analysis of pulled-out fibre
• Optical and SEM images of pulled-out fibre
Mounting cradle ION-TOF sample platen ION-TOF TOF.SIMS 5
A R Wood, P A Smith, J F Watts, Comp Interf, 14, 287, (2007)
The Surface Analysis Laboratory
Mechanical Testing
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.60 0.80 1.00 1.20 1.40 1.60 1.80Extension (mm)
Forc
e (N
)
Load cell
Swivel links
Fibre carrier needle
Mould cap
Mounting bolt
Crosshead adapter
Material df (μm) L (μm) Fmax (N) τ (MPa)
Glass/Polyester 12.2 849 0.157 4.8
The Surface Analysis Laboratory
Positive ToF-SIMS Spectra
Mass (u) Formula Characteristic Structure
91 [C7H7]+ Polyester resin
105 [C7H5O]+ Polyester resin
115 [C9H7]+ Polyester resin
149 [C8H5O3]+ Polyester resin
O+
Mass (u) Formula Characteristic Structure
58 [SiC2H6]+ PDMS/Silane/N species [SiC2H6]+
73 [SiC3H9]+ PDMS/Silane
135 [C9H11O]+ Glass fibre size (epoxy)
OH C+
CH3
CH3
CH3 Si CH3
CH3
Pulled-out fibre tip
Si K
Ca
Si C2H6
Si C3H9
C7H7 C7H5OC9H7
C9H11O
Si2C5H1 5O C8O3H5
Si K
Ca
Si C2H6
Si C3H9
C7H7
C7H5O
C9H7C9H11O
Si2C5H15O C8O3H5
m ass / u20 40 60 80 100 120 140 160 180
3x10
1. 0
2. 0
3. 0
4. 0
5. 0
Inte
nsity
4x10
0. 5
1. 0
1. 5
Inte
nsity
Pre-embedded fibre tip
Pulled-out fibre tip
+
O
O
O
H+
•Bi3+
•Bunched mode
•128 μm x 128 μm
•128x128 resolution
The Surface Analysis Laboratory
In-Situ Controlled Strain RateFracture
Controlled strain rate + load cell + PC control = Load: Extension curve in situ
The Surface Analysis Laboratory
Correlation of XPS with Electrochemical History
The Surface Analysis Laboratory
Corrosion Beneath Organic Coating
Anodic Region
Cathodic Region25 μm
The Surface Analysis Laboratory
SAM Identifies Cathodic Regions
SEM Ca LMM CKLL
OKLL FeLMM NaKLL
The Surface Analysis Laboratory
NIST SRM Multilayer
• Superb Depth Resolution from metal multilayer structure (layer thickness only 5nm), achieved by:
– Low ion beam energy
– Azimuthal rotation of specimen during sputtering cycle
– Almost grazing incidence analysis by use of specimen tilt
The Surface Analysis Laboratory
Chemical State Mapping
High energy resolution (0.1%) Cu maps allow
separation of Cu and CuO
The Surface Analysis Laboratory
AES/EDX of Inclusions in Steel
Field of View ca. 5 μm
SAM Provides Superior Spatial Resolution to EDX
Grain Boundary Embrittlement
This phenomenon renders engineering steels brittle in nature as a result of the presence of sub-monolayer
quantities of impurities at grain boundaries and phase boundaries.
This can be studied by examining such fracture surfaces by AES but if fracture in air the steel will oxidise and obscure
the analytical signal of the segregant.
In Situ Fracture Studies by AES
For the study of grain boundary segregation phenomena in metals the sample must be
fractured, in an intergranular manner, within the UHV of the
Auger microscope
In Situ Fracture of Steels
Although predominantly intergranular failure this
micrograph shows a region of transgranular
failure in the centre of the field of view. This
provides a convenient “standard” spectrum of
the bulk steel
In Situ Fracture 3Cr-0.5Mo Steel
Hot Cracking of Austenitic Steel Weldment: AES and EDX
AES: S, EDX: Cr
Hot Cracking of Austenitic Steel Weldment: AES and EDX
EDX alone would indicate that the enhanced Cr was a result of the present of Cr2O3 in crack. AES data alone would indicate that sulphur segregation
is the cause of ductility-dip cracking.
AES and EDX together indicates a second Cr-rich phase has formed at grain boundaries:
Liquation Cracking
The Surface Analysis Laboratory
Conclusions
• All three techniques have various hierarchies of use ranging from simple elemental analysis to in-depth chemical characterisation at high spatial resolution
• XPS, AES and SIMS are powerful analytical methods for the chemical and elemental characterisation of surfaces
• For metallurgical studies AES/SAM is perhaps the most useful
• For polymers a combination of XPS and ToF-SIMS is hard to beat
• Surface analysis is expensive!• So start with a service lab such as SI-O or University of
Surrey!