Characterization of Ti-based surfaces with X-ray ... Workshop Slovenia/BioTiNet_Kovac.pdf · X-Ray...

Characterization

of

Ti-based surfaces

with

X-ray

photoelectron

spectroscopy

Janez KovačJožef Stefan InstituteLjubljana, Slovenia

E-mail: [email protected]

mailto:[email protected]

Outlook•

X-Ray

photoelectron

spectroscopy

–

Principles–

Surface

sensitivity

–

Quantification–

Chemical

shift

–

Instrumentation–

Depth

profiling

•

Applications

of

XPS and

AES–

Ti valence states

on Ti-O ceramics

–

TiO2 anatase

layer/Ti6Al4V alloy–

Rejected

Ti implant

from

a patient

X-Ray Photoelectron Spectroscopy- XPS

•

Irradiation of solid surface with monohromatic

X-ray photons (E~1000 eV, λ∼1 nm) and energy analysis of emitted photoelectrons

•

High surface sensitivity

•

Information on:–

Composition

–

Chemical state of elements

X-raysemittedelectrons

XPS – Photoelectron process

EFermi

Valelence

band

X-ray

photon, hν

Emitted

electron, EK

EVAKUUM

1 s

2 s

2 p

Energy

levels

in carbon Bind

ing

ener

gy(e

V)

XPS spectrum•XPS peaks: 1s, 2s, 2p...

•Spin-orbit splitting: 2p3/2

,2p1/2

•Valence band

•Auger

peaks

•Background

due

to inelasic

scattering

XPS survey

spectrum

of

InP

Binding

Energy

(eV)

Kinetic

Energy

(eV)

020040060080010001200

Binding Energy (eV)

Inte

nsity

(a.u

.)

InP(100)

Concentrations:In...31.6 at.%C...29.0 at.%O...27.0 at.%P...12.4 at.%

In 3p

In 3d

O 1s

C 1sP 2s P 2p

In 4dO KLLIn 3s

Surfacecontamination

Surface sensitivity

Inelastic

mean

free

path

–

IMFP: λ

~ 0.3 -

4

nm

95% of the measured peak intensity comes from a sampling depth of 3λi cosθ

(θ=angle of emission)

Quantificationλσ ⋅⋅⋅⋅= KcjI

j -

x-ray flux

c -

concentration of element

σ -

cross-section for photoelectron excitation

K -

instrumental factors

λ - electron inelastic mean free path

∑=

j j

j

i

i

i

SIS

I

cSi

: Relative

sensitivity

factorCi

: concentration

in at.%

• Sensitivity of XPS ~ 0.1 at.%• Possible to detect all elements except H and He

Chemical shift in XPSElectrons at inner orbitales (core

levels) feel different potential due to different chemical bonds of atom by valence electrons

⇒

change in binding energy = chemical shift (up to few eV)

⇒

Model: ΔE=

k

Δq + ΔV

(charge potential model)

⇒

information about:1.

Valence states

2.

Chemical environment

450455460465470475Binding Energy (eV)

Inte

nsity

(a.u

.)

Ti 2p Ti 2p3/2

Ti 2p1/2

Ti (4+)TiO2


Inte

nsity

(a.u

.)

Ti 2p Ti 2p3/2

Ti 2p1/2

Ti (4+)

Ti (3+)

Ti (2+)

Ti-suboxides

Chemical shift in XPS: a tool

to recognize

chemical

compounds

UHV ambient•

Why a need for UHV?–

10-8

to 10-10

mbar

•

Surface contaminationat 10-6

mbar, a monolayer of gas is adsorbed onto solid surface in about one second

•

Scattering of photoelectrons

XPS spectrometer

Complex, ultra high vacuum instrument:

•

X-ray sources, •

electron

energy

analyser,

•

ion gun, •

neutralizer,

•

sample manipulator•

p ~ 10-10

mbar

X-ray sources for XPS•

X-ray tubes (laboratory):–

Mg anode, E=1253.6 eV, FWHM=0.70 eV

–

Al anode, E=1486.6 eV, FWHM=0.85 eV

Quartz monochromator

(FWHM ~ 0.25 eV)

•

Synchrotron radiationtunable

energy, high flux, high monochromaticy, very

small

spot X-ray

beam

(<100 nm)(Synchrotron

Elettra

at Trieste

(IT)

ApplicationsStudies of phenomena at surfaces and interfaces:

•

oxidation, •

adhesion,

•

adsorption, •

contamination,

•

segregation, •

diffusion,

•

surface

functionalization•

reactions

at internal

interfaces

•

thin

films•

…

Effect

of the valence state of titanium ions on hydrophilicity

of

ceramics in Ti-O

system

•

TiO2

: photocatalytic

and

superhydrophilic

effects

•

To study

effect

of

valence states

of

Ti-atoms

on WCA

•

TiO2

ceramic was prepared from TiO2

powder sintered in air, •

reduced TiO2-x

ceramic from TiO2-x

powder sintered in Ar/H2•

Ti2

O3

ceramic from mechano-

chemically activated Ti2

O3

powder sintered in Ar/H2

.

•

All powders were sintered at 1400 oC

for 2 hoursSEM image of TiO2−x powder and (b) X-ray powder-diffraction

pattern of TiO2−x powder.

D. Kuščer et

al., Journal of the European Ceramic Society 28 (2008) 577–584


Inte

nsiti

es (a

.u.) O KLL

O 1s

Ti 2p

C 1s

Ca 2p

Mg KLL

Ti 3p

Si 2p

Ba 3d

Ti LMM

TiO2

TiO2-x

Ti2O3

Effect


of

ceramics in Ti-O

system

D. Kuščer et


455460465470475

Binding Energy (eV)

Nor

mal

ized

Inte

nsiti

es(a

.u.) Ti 2p Ti4+

Ti3+

TiO2

TiO2-x

Ti2

O3Ti3+/Ti total

9 %

14 %

0 %

D. Kuščer et


Effect


of

ceramics in Ti-O

system

Effect


of

ceramics in Ti-O

system

454456458460462464466468470

0

500

1000

1500

2000

2500

3000

Ti 2p spekter, vz. 2, TiO2-x

Vezavna energija (eV)

Sign

al (i

mpu

lzi/s

)

3+ 3+

4+

4+

D. Kuščer et


-

The

presence

of

Ti(3+) at surface

is related

to a significant

decrease

in water-contact

angle.

-

Wettability

of

ceramics

in the

TiO

system

can

be

improved

by

introducing Ti(3+) at the

ceramic

interface.

TiO2-xTi 2p

18

26

67

0

10

20

30

40

50

60

70

80

Ti2O3 TiO2-x TiO2

Wat

er c

onta

ct a

ngle

(deg

ree)

Surface subsurface

•

Very

often

information

from

subsurface region

needed.

•

Depth

profiling: –

Angle

resolved

XPS: depth

up to 10 nm

–

Ion sputtering: depth

up to 500 nm

Ion sputter depth profiling

OVERLAYER

SUBSTRAT

EL. OR X-RAY BEAM

Schematic representation of the beginning of the AES/XPS depth

profiling analysis.

ION BEAM

XPS depth

profiling

with

high

depth resolution

Cr-oxide Cr-oxideCr-metalCr-metal

Ni Cr

O

Cr

Ni Cr

Si

XPS depth

profile ofNi(30 nm)/Cr(30 nm)/Cr2O3(30 nm)/Ni(30 nm)/Cr(30 nm)/Si structure

depth

Ion sputter depth profiling•

Techniques:–

XPS or Auger

electron

spectroscopy

–

AES

•

Information:–

Depth

distribution

of

elements

in layer

of

thickness

of

about

100 -

500 nm

•

Requirements

for–

Good

depth

resolution, sample

rotation

(invented

by

prof. Zalar

in 1985 in our

laboratoy)

•

Drawback: destructive

method, reduction

of

Ti valence states

•

Alternative techniques–

TEM, RBS, FE-SEM, GDOES, SIMS

Hydrothermal

synthesis

of

anatase layer

on Ti6Al4V implants

-

V

has been reported to be cytotoxic-

Al has been suggested to be neurotoxic

N. Drnovšek et

al., Surface & Coatings Technology 203 (2009) 1462–1468

TiO2

layer present at the surface:• it

has some bioactive properties

• to prevent diffusion of toxic metal

ions into the

body

Non

treated After

24h at pH=8, 150 oC, with

TiO2

addition

Hydrothermal

synthesis

of

anatase

layer

on Ti6Al4V implants

SEM images of HT treated Ti6Al4V specimens with TiO2

addition. (a) pH=8 (natural). The surfaces of the substrate are covered with a thick layer of large anatase

crystals.

(b) pH=11. The size of anatase

crystals is reduced.

Sample

preparation:

at different pH values with or without the addition of TiO2

(anatase

powder) or Ti(OH)4

in water

suspension

or NaOH

or NH4

NO3

solution

Result: different

morphologies of anatase

crystals and different thickness of the oxide layer


Inte

nsity

(a.u

.)

Ti 2p

Ti 2p1/2

Ti 2p3/2

E=458.8 eV(TiO2

)

XPS spectrum of Ti 2p obtained on the surface of the sample treated by HT in the NaOH

soultion

N. Drnovšek et



Inte

nsity

(a.u

.)

C 1s

Ti 3p

Ti 3s

N 1s

O 1s

Ti 2pTi 2s

V 2p

Al 2p

Ar 2p

Surface

At depth~ 750 nm

XPS spectra

obtained on the surface and

at depth

of

750 nm

of the sample treated by HT in the NaOH

soultion

Difference

in presence

of

metals: V and

Al not detected

at surface

N. Drnovšek et


Depth

profiles

of

TiO2

/Ti6Al4V

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90

Sputtering Time (min)

Con

cent

ratio

n (a

t.%)

C (at.%) O (at.%) Al (at.%) Ti (at.%) V (at.%)

O

Ti

CV

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90


Con

cent

ratio

n (a

t.%)


O

Ti

C

V0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100


Con

cent

ratio

n (a

t.%)

C1s O1s Al2p Ti2p V2p

O

Ti

AlCV

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40


Con

cent

ratio

n (a

t.%)


O

Ti

AlC

V

- Thick layer of TiO2 after treatment of Ti6Al4V in TiO2 suspension

- No Al found in TiO2 layer

- Low amount of V incorporated in the anatase structure

Non-treated HT-treated

in Ti(OH)4

suspention

HT-treated

in TiO2

suspention HT-treated

in NH4

NO3

solution

OSSEOINTEGRATION AND REJECTION OF A TITANIUM SCREW

Grega

Klančnik

et

al., Materiali

in tehnologije

/ Materials and technology 44 (2010) 5, 261–264

Titanium screw –

rejected implant

0

5

10

15

20

25

30

35

40

0 50 100 150 200 250 300 350 400Depth (nm)

Con

cent

ratio

n (a

t.%)

P C Ca N Ti O Fe Mg Al Si

O

C

Ti

N

Si

Al

CaMg

Fe

Ti

P

Orthopaedic

screw

removed from

patient

due

to irritation

Screw

was

for

one year

in metacarpal

bone

Surface of screw was nitrided (TiN)

Formation of hydroxyapetite (Ca, P, O)

Si and Al (to reduce friction)


Titanium screw –

rejected implant

0

1

2

3

4

5

0 50 100 150 200 250 300 350 400Depth (nm)

Con

cent

ratio

n (a

t.%)

P C Ca N Ti O Fe Mg

P

Ca

Mg

Fe

Grega

Klančnik

et

al., Materiali

in tehnologije


Orthopaedic

screw

removed from

patient

due

to irritation

Screw

was

for

one year

in metacarpal

bone


Titanium screw –

rejected implant

•

Surface contamination:–

Fe (iron containing steel tool)

–

Si and Al (to reduce friction)

•

Accumulation of Fe and Al can cause inflammation, irritation and rejection of Ti-

screw

Grega

Klančnik

et

al., Materiali

in tehnologije


Orthopaedic

screw removed from patient

due to irritation

Screw was for one year in metacarpal bone

Conclusions

•

XPS is suitable technique for characterization of surface chemistry on model and realistic samples yielding information on surface composition and chemical state of elements.

•

In combiantion

with ion sputtering XPS and

AES techniques

can provide information of

distribution of elements in subsurface region

Characterization

of

Ti-based surfaces

with

X-ray

photoelectron

spectroscopy

Janez KovačJožef Stefan InstituteLjubljana, Slovenia

E-mail: [email protected]

mailto:[email protected]

Characterization of Ti-based surfaces with X-ray ... Workshop Slovenia/BioTiNet_Kovac.pdf · X-Ray...

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