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Lecture22
SurfaceCharacterization
Unlessotherwisenoted,sourceInformationforthefollowingslides:
1)
B.Ratner,A.Hoffman,F.Schoen,andJ.Lemons:BiomaterialsScience,2nd
edition(SanDiego:ElsevierAcademicPress.2004).
2) Modifiedfrom:Anne
Mayes3.051J/20.340JMaterialsforBiomedical
Application,MIT,http://ocw.mit.edu,
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SurfaceCharacterizationof
Biomaterials:Vacuum
Techniques
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ray otoe ectron pectroscopy
(XPS)
Physicalbasis:photoionizationandemissionof
core
level
electrons
upon
irradiation
with
X
rays
XPSspectrallinesareidentifiedbytheshellfromwhichtheelectronwasejected(1s,2s,2p,etc)
Surfacesensitive(1 10nm)
Quantitative countingelectrons!But
accuracydependsonthequalityoftheatomicsensitivity
factors
Sampledegradationisanissue!
Enablesanalysisofcomplexsurfacechemistries
Automatedhigh
throughput
(at
least
for
high
vacuumtechniques)
Valence Band
Conduction Band
Ejected PhotoelectronIncident X-ray
2p
2s
1s
L2,L3
L1
K
Free e-
level
Fermi
level
SpecBEhKE
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AreaunderpeakIiproportionalto
numberof
electrons
ejected
(&
to
numberofatomspresent)
Onlyelectronsinthenearsurface
regionescapewithoutlosing
energybyinelasticcollision
Sensitivity:dependsonelement.
Elementspresentinconcentrations
>0.1atom%aregenerally
detectable(H&Heexceptions,
nondetectable)
XPS
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High
Resolution
XPS
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High
Resolution
XPS
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Quantification:
Peak
FittingHigh Resolution C 1s and O 1s Spectra of p(S-co-MMA)
Brush
2)/(3
)/(8
exp
exp
CO
COFMMA1)/(3
)/(8
expCCO
expCCO
II
IIFMMA
Survey Method High Resolution Method
where is the O/C ratio
obtained from XPSexp)/( CO where is the ratio
of the carbonyl C to the total C
)/( CCO II
Ton-That et al. Polymer2001, 42, 1121.
m n
OO
CH3
C2
C2 C1C1
C4C
5
C3
C2
m n
OO
CH3
O1O2
C1
C2C3
C5
C4 O1O2
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XPS CopolymerComposition
Gradient X-ray photoelectron spectroscopy (XPS) was used to map
the surface
composition of the statistical copolymer brush gradients
Spectra collected at 4 mm intervals along the gradient
substrate
Survey Spectra
C 1s
High Resolution Spectra
O 1s
C 1s envelope
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XPS CopolymerComposition
Gradient X-ray photoelectron spectroscopy (XPS) was used to map
the surface
composition of the statistical copolymer brush gradients
Spectra collected at 4 mm intervals along the gradient
substrate
Survey Spectra
C 1s
O 1s
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DepthProfilingwithXPSatDepths>10nm
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SIMS
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SIMS
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SIMS
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SIMSModesofOperation
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SIMSModesofOperation:
Exampleof
Static
Mode
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SIMSModesofOperation:ExampleofDynamicMode
