Course I.a. XPS Basics

8/18/2019 Course I.a. XPS Basics

1/120


2/120

The slides are readable on rints

of ! or " slides er #$ sheet

%


3/120

Course I.

Surface analysis by XPS

Basic aspects

&ith ac'no(legments of contributions from

)hristine *uont and +ichel enet

Paul G. Rouxhet

Prof. emeritus, Université catholique de LouvainLouvain-la-Neuve, Belgium

[email protected]

1st Colombian Seminar on Surface Science

Bucamaranga, 23-27 November 2015


4/120

XPS - Basic aspects

Sco!e " #$%sical !rocess & instrument &

c$emical information & surface selectivit% ' global vision an( critical min(

-ra/s and electrons

0ssence of P

2nstrumental asects3eatures of a P sectrum

4uantification

)hemical shift

Time line

$

+.5. enet, ).). *uont-illain, P.. 6ou7het

)#S anal%sis of bios%stems an( biomaterials

in +edical alications of colloids 8ed. 0. +ati9evic:,

ringer, Ne(-;or' %-

Practical reference: close to the course, can be forwarded on request


5/120

Incident Attenuation Primary Secondary emission

particle emission 6adiat. rela7ation #uger effect

#! ? e #! # ? hν #! # ? e

#bsortion s. Photoelectron s. 3luorescence #uger ea's

Surface anal. Elemental anal. in P sec.

hν

-6a/ imaging -ra/ filter

Transmission 0lectr. microrobe #uger sec.

electron micr . Element anal. Surface anal. 0lectr. energ/ + space resolut. + space resolut.

e loss sec. imaging imaging

-ra/ source canning

electron micr.

orpholog!, imaging

-ra/s and electrons

@


6/120

!

"lectron orbitals

hell subshell AA l 8< to n-1: ml 8- l < ?l:

n orbital shae

angular moment orientationd % -%, -1,


7/120

>

EEEEEEEEEFero binding levelEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

E

d @A% EEE E

d A% EEE EEEE

A% EEE EEE + series E

1A% EEE EEEEEE E

s 1A% EEE EEEEEE

% A% EEE EEE E%A% EL222 E

% 1A% EEE EEEEEE L series E%1A% EL22 E

%s 1A% EEE EEEEEE E%s EL2

1s 1A% EEE EEEEEE G series E1s EG E E EE

ccupation /ame XPS pea0s X-ray X-ray

in X-ray absorption emissions ectrosco ed es lines

Gα1Gα%

Gβ

-ra/s and electrons


8/120

=

EEEEEEEEEFero binding levelEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE E

d @A% EEE E %$=$

d A% EEE EEEE > %@=@

A% EEE EEE

1A% EEE EEEEEE @$ @@$ E

s 1A% EEE EEEEEE " =@<

% A% EEE EEE >%1 1@%11% ==


9/120

"

3e Gα, >.11 - 1

3e Gβ, >.11 -


10/120

2on1ersion bet3een ener,y and 3a1elen,th of photon

0 C h ν C h c A λ C !.! 1


11/120

11

1%$


12/120

1%

EEEEEEEEEFero binding levelEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE E

d @A% EEE E %$=$

d A% EEE EEEE > %@=@

A% EEE EEE

1A% EEE EEEEEE @$ @@$

s 1A% EEE EEEEEE " =@<

% A% EEE EEE >%1 1@%11% ==


13/120

1

Photoemission

h ν

Principle

Photoelectron $s

(ith 'inetic energ/ "0

0ssence of P


14/120

1$

) o u n t s

Kemisherical electron

energ/ anal/Fer

0lectron multilier 6etardation

stage-ra/s

E "

e

amle

) o u n t s

hemisherical electron

energ/ anal/Fer

electron multilier retardation

stage-ra/s

E "

e

samle

"0 4 hν + "b

"b electron binding energ/

ea' characteristic of a given element

elemental analysis

GoomanMs aro7imation binding energ/ C energ/ required to remove e

from energ/ level to ∞ assuming no rearrangement of other electrons

0ssence of P


15/120

f


16/120

1!

"ner,y le1els of selected elements

0ssence of P

0 f P


17/120

1>

Global 1ie3 of photoelectron spectroscopy

Information related to energ/ levels

- anal/tical asects elemental comosition

atom environment chemical functions

- theoretical chemistr/ electron energ/ levels

molecular orbitals

0nerg/ levels - core, (ith -ra/ XPS, 0)#

- e7ternal, (ith UH 5PS

0ssence of P

0 f P


18/120

1=

From principle to measurement

"06 4 "0 + Φsp + "c

4 hν

+ "b + Φsp + "c

-

Φs sectrometer (or' function, (or' sent to bring efrom Fero attraction b/ the samle to entrance of anal/Fer

0c

case conductor C <

case of insulator, samle charging

0ssence of P

0 f P


19/120

1"

$


20/120

%<

P & d' (

'

d'

P & d'

θ

2ontribution of a layer of thic0ness d8 at depth 8

) concentration of hotoelectron emitor in homogeneous solid

P constant for a given element and level 8robabilit/ of electron emission:

and for a given e7lored area

#ttenuation 4 C e7 8- F A λ cos θ:

X-ray

hν

e

0ssence of P


21/120

0ssence of P


22/120

%%

P & e78-' Aλ cosθ:

P &

P &

FAλ cosθ

<

1

%

$

P & e78-' Aλ cosθ:d' P & λ cosθC

2ontributions of increasin, depths

assuming that ) is constant

!

=!

"@

"=

cumulated

0ssence of P

∫ ∞

0

0ssence of P


23/120

%

P & e78-' A λ cosθ:

P &

P &

FA λ cosθ

<

1

%

$

P & e78-' A λ cosθ: d' P & λ cosθC

2ontributions of increasin, depths

!

=!

"@

"=

cumulated

2f the solid has a homogeneous comosition, things haen

as if the ea' (as due to a la/er of thic'ness λ cos θ and the hotoelectron intensit/ (as not attenuated

0ssence of P

∫ ∞

0

0ssence of P


24/120

%$

Illustration< oxidation of ,ermanium0ssence of P

0ssence of P


25/120

%@

θ C


26/120

XPS - Basic aspects

-ra/s and electrons

0ssence of PInstrumental aspects

vacuum

-ra/ source

energ/ anal/Fer

detectionsurface charging

miscellaneous

%!

Hacuum


27/120

Gratos #7is Ultra

Hacuum

%>

Hacuum


28/120

to reduce

• inelastic collisions bet(een hotoelectrons and gas molecules

• detector, gauges degradation 8electrical discharges:

• surface contamination 8:

/eed of 5ltra =i,h >acuum conditions

#im 1 Pa

Practice Q1


29/120

2oolid,e tube

ource

%"

ource


30/120

1.$=!,! eH 1.%@,! eH

Source 3ithout monochromator

N.B. Sther less common anodes r 81@1.$ eH:R i 81>".! eH:R

#g 8%"=$ eH:R Ti 8$@1


31/120

? " :e>;

I

1

1$=>

Gα1,%

Gα,$

Gβ

X-ray emission spectrum from an aluminum source

bremsstrahlung

1.$=!,> eH 2nt %A

1.$=!, eH 2nt 1A

ource

*ue to

slo(ing do(n of e in

the atom atmoshere

Gα,$ due torela7ation of #l??J

1

R di ti filtource


32/120

? " :e>;

2

1

1$=>

Gα1,%

Gα,$

Gβ

bremsstrahlung

1@!< eH

0mission sectrum of aluminum

#bsortion sectrum of aluminum absortion edge G

Radiation filter ource

%

S t llit d t thource


33/120

x 103

8

10

12

14

16

18

20

570 560 550 540 530 520 510Binding Energy (eV)

S 1sdue to G

α1,%

Gα@,!

Gβ

Gα,$

Satellites due to the source

', source

ource

"b

G α1,% 0'C h ν - 0b

#α

(*@

6eal 0s' C h νs - 0b #arent 0b

a C h ν - 0s'

C h ν - h νs ? 0b

∆ C 1< eH

etc

0ba

due to

33

ource


34/120

Source 3ith monochromator

#l

#l Gα1,%

election of (avelength through diffraction b/ a cr/stal

8BraggMs la(:

remo1es #α(*@

sharpens #α

$*&

ource

$

ource


35/120

"ffect of monochromati8ation

C 1s on #ol%*et$%lene tere!$t$alate - #/

+onochromatisation reduces the (idth of Gα1,% line,

Gα% contribution is drasticall/ reduced

2 n t en s i t / 8 a. u. :


36/120

#nal/Fer


37/120

2oncentric =emispherical Analy8er :2=A-=SA:

0lectrons of energ/ 0 in9ected tangentiall/ in

circular orbits of radius 6

/

2

2

2

1

2121 )(

R R

R RV V e E

p−

−=

#nal/Fer


38/120

0lectrons (ith lo(er or higher energ/ than 0

ath radius smaller or larger than 6


39/120

0

0ntrance and e7it slit (idth

0ffective resolution ∆0eff C 8∆0A∆6: &

C 80A % 6


40/120

)

o u n t s

Kemisherical electron

energ/ anal/Fer

0lectron multilier 6etardation

stage-ra/s

E "

e

amle

)

o u n t s

hemisherical electron

energ/ anal/Fer

electron multilier retardation

stage-ra/s

E "

e

samle

"0

0'det C 0ass C 0' - 0ret

)onstant anal/Fer energ/ mode V

0ass constantR 0' s(et b/ s(eeing 0ret

resolution constant in recorded spectrum $<

#inetic ener,y analysis

/

#nal/Fer


41/120

2 1


42/120

$%

Pea's height normaliFed

A r b i t r a r y u n i t

! 1

Pa energy 20 eV

544 542 540 538 536 534 532 530 528

Binding Energy (eV)

Pa energy 20 eV

2"0 280

Binding Energy (eV)

A r b i t r a r y u n i t

0 C %< eH

0 C $< eH

0 C %< eH

0 C $< eH

P0T

$s 2 $s

"ffect of "pass on spectrum resolution

/

#nal/Fer


43/120

"lectrostatic input lens

• Transfer a magnified image of the

anal/sed area from the samle lane

to the entrance slit lane of theanal/Fer

• +ore free sace around the samle

• 6educe image distortion

• #cts as a retardation stage

0'det C 0' - 0ret 6etarding otential

$

#nal/Fer


44/120

'a,netic lens

amle immersed in

a magnetic field

• amle to be suorted at some distance

from the electrostatic lens

• Kigh collection efficienc/ 8high collection angle:

• Kigh satial resolution

• The current trough the lens is varied according to 0'Gratos #7is ultra

$$

#nal/Fer


45/120

S7/gen lasma treated ol/str/rene

@

1<

1@

%<

%@

<

@

$<

$@

@<

%"! %"% %== %=$

Binding 0nerg/ 8eH:

2 $s

=ybrid mode combination of

electrostatic end magnetic lens

"lectrostatic mode

electrostatic lens onl/

Gratos #7is Ultra

ith ma,netic lens< hi,her intensity and impro1ed resolution

2omparison bet3een lens modes

hi,her efficiency of char,e stabilisation de1ice

45

A l d b b d d #nal/Fer


46/120

Analy8ed area 1ersus bombarded area

X-ray e-

X-ray e- X-ray e- X-ray e

-

Bombarded

area

Sld generation 2 1

Gratos #7is Ultra

H 0)#L#B %@


47/120

Analysed area 1ersus Bombarded area

2oncern

- #nal/Fed sot siFe

- Hariation of ta'e off angle - change of Fone anal/Fed

- Possibilit/ to e7loit focused -ra/to avoid degradation of sensitive samles

8dislacement of samle osition during anal/sis:

$>

"ffect of spot si8e on spectrum #nal/Fer


48/120

2 1


49/120

#nal/Fer


50/120

#inetic ener,y scale

0M'C h ν - 0b - Φs

Φs (or' function of sectrometer

*etermination C calibration of 8ero of 0' scale

2S #g d@A% C !=.%> ±


51/120

XPS - Basic aspects

-ra/s and electrons

0ssence of PInstrumental aspects

vacuum

-ra/ source

energ/ anal/Fer

detection

surface charging

miscellaneous

@1

Sample char,in,urface charging


52/120

-ra/se-

Sn conductors "2 4 E Sn insulators "2 E

????????

-ra/se-

Sample char,in,

h ν, hoton energ/ 0', electron as roduced0M', electron as measured Φs, (or' function0), charging term

0M'C h ν X 0b - Φs - 0) 0'C h ν X 0b - 0)

@%


53/120

2har,e stabili8ation

ther de1ices according to manufacturer

Flood ,un flooding the surface (ith lo( 'inetic energ/ electrons 82:

"2 E

2 1


54/120

2har,e stabilisation (ith 2har,e Balance de1ice

Gratos #7is Ultra

#agneti$ %ie&d &ine

Sa'&e

*$ued +*t*e&e$tr*n

Se$*ndary

e&e$tr*n

returning t*

a'&e

,nder%*$ued

+*t*e&e$tr*n

V

neg

C+arge ba&an$e &ate

-.ray

"ntrance Slit

e-

54

a, #dventitious carbon on stainless steel


55/120

2 $s

0b C %=$.= eH

a, d e ous ca bo o s a ess s ee

+onochrom., charge stabiliFer S33

2onductin, sample "2 ≈ E

----------------------------------------------------------

-Pol/8eth/lene terehthalate: X P0T

Insulatin, sample

b, Not monochrom. (ithout flood gun

"2 ≈ C.H e>

c, +onochrom. ? charge stabiliFer C ≈ - e>

d, +onochrom. ? charge stabiliFer

C ≈ - $.@ e>

----------------------------------------------------------

-

e, +onochrom. ? charge stabiliFer

'ixed sample 2nsulating ? )onducting

iffer.charg. C

≈

- $E e> C

≈

E e> JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ EE JJJ @@

S l h iurface charging


56/120

Sample char,in,

0'C h ν X 0b - 0)

Problem variation of 0) - accross the samle

- as a function of time

ea' broadening

distortion

shift

)fr )ourse 2,)

@!

+iscellaneous


57/120

Po3der in trou,h

Trough

8internal

diam. $ mm:

Pol/acetal

c/linder

*eth

+iscellaneous


58/120

Po3der in trou,h

Trough

8internal

diam. $ mm:

Pol/acetal

c/linder

Po3der sensiti1e to air exposure

isooctane

isooctane

sectro

*eth


59/120

ecimen holder

*ouble sided adhesive tae8conductive or insulating:

+assive or Po(dered

Specimen on holder

ther preparation methods<

dr/ing (ith a flu7 of nitrogen gas

cells freeFe-dr/ing

adsorbed biomolecules

ecimen holder

*ouble sided adhesive tae8conductive or insulating:

+assive or Po(dered

@"

+iscellaneous


60/120

Gratos #7is Ultra

'ulti samples bar

2opper Stub

!<

+iscellaneous


61/120

Sputterin, 3ith ion ,un

Bombardment of samle (ith a beam of argon ions

suttering - surface cleaning

- comosition rofile

*anger alteration of anal/Fed Fone

!1

Remo1in, or,anic contamination+iscellaneous


62/120

2 n t en s i t / 8 a. u. :

%"% %"< %== %=! %=$ %=% %=<Binding 0nerg/ 8eH:

2on suttering

K 2arbide K

before

after

2 $s

Remo1in, or,anic contamination

tainless steel cleanedV b/ ion suttering

!%

+iscellaneous


63/120

Ion Gun

2amera on SA2

=eatin,)2oolin,

de1ice in F"%

:$DEL2)-$CDL2;

Par0in, facility

2atalyst 2ell

2atalyst 2ell

!


64/120

!$

XPS - Basic aspects

Photons and electrons

P elemental anal/sis (ith surface selectivit/

2nstrumental asects

3eatures of a P sectrum

core hotoelectron ea's and bac'ground #uger ea's

energ/ scale referencing

valence band

addtional features

Pea's and bac'ground


65/120

/a'e

C 1

P*

28300

#

3011

Area

3757"6

At

10000

x 104

0

5

10

15

20

25

30

35

40

C P S

1000 800 600 400 200 0

Binding Energy (eV)

Sur1ey spectrum of polystyrene

2 $s

bac0,round

"b"0

te due to hotoelectrons(ith same origin as the ea'

but having undergone

inelastic collisions

!@

Pea's and bac'ground


66/120

Sur1ey spectrum of colla,en*free+e-(rie( !o(er

1<

%<

<

$<

@<

!<

><

1


67/120

Bac0,round 1ariationPea's and bac'ground


68/120

!=

JJ

J

S 1 s

S G L L

S

)

1

i % s

i %

7 1<$

<

@

1<

1@

%<

%@

<

S 1 s

S G L L

S

)

1 s

i % s

i %

7 1<$

<

%

$

!

=1<

1%

1$

1!

1=

1


69/120

oublets

Glass

<

@

$<

$@

@<

@! @% $= $$Binding 0nerg/ 8eH:

)a %

2a &p$)&

2a &p()&

0lectron energ/

levels

1s

%s

%1A%

%A%

!"

Relaxation by Au,er emission#uger ea's


70/120

><

Photoemission

:XPS;

6ela7ation

Au,er "lectron"mission

8#0, #0:

-ra/

3luorescence

GL1L%,

h ν

or

1s

Relaxation by Au,er emission

#uger ea's


71/120

>1

#uger ea's


72/120

Position of Au,er pea0s in XPS spectrum

"60*#%% 4 "b*# + "b*%$ + "b*%& + Φsp + "c

energ/ liberated

energ/ consumedmeasuredkinetic energy

>%

& dislacement of energ/ levels

uon formation of a doubl/ ioniFed atom

#uger ea's


73/120

Position of Au,er pea0s in XPS spectrum

does not depend on hν

"60*#%% 4 "b*# + "b*%$ + "b*%& + Φsp + "c

energ/ liberated

energ/ consumedmeasuredkinetic energy

E’k = hν - Eb – Φsp – Ec

>

Illustration< Stre!tococcus t$ermo!$ilus


74/120

-ra/ source +g,

not monochromatiFed

1%@$ eH

-ra/ source #l,monochromatiFed

1$=> eH

2 n t e n s i t / 8 a . u . :

8eH:

8eH: b :e>;

:e>;

:e>;

atch

#uger vs hotoelectrons2nfluence of source

0' and 0b scales

ea' osition

bac'ground

>$

#uger ea's


75/120

2 n t e n s i t / 8 a . u . :

8eH:

8eH: b :e>;

:e>;

:e>;

Au,er parameter

α

4 "0*Au,er:#%%; + "0*XPS:#;

α

6 4α

hν

4 "0*Au,er:#%%; "b*XPS:#;

α

+odified #uger arameter

α

*s compared with E b of photoelectrons,

$ more sensitive to chemical state

$ independent of calibration of

the 'ero of energ! scale

>@

0nerg/ scale referencing


76/120

2onductin, sample< "c 4 E

Calibration of energ% scale using a stan(ar( *u, Cu

Use of an identified ea' 0bJ determination of Φs

Fero of 0' scale direct conversion of 0'M to 0b

Use of several identified ea's chec' of energ/ scale linearit/

Insulatin, sample< "c M E and particular to the sample

Calibration of b scale

Use of an identified ea' of the samle 0bJ

determination of Φs ? 0) conversion of 0'M to 0b

)ommon ractice ) 1s of alihatic h/drocarbon

2-:2*=; set at &[email protected] e>

measured

0b C h ν X 0' C h ν X 0'M X Φs X 0c 'no(n

>!



77/120

Polylactic acid

2-8),K: Y %=$,= eH

67eamson and 7riggs, #8849>>



78/120

67eamson and 7riggs, #8849

Polystyrene

) alihatic

Y %=$,= eH

) aromatic

Y %=$,! eH

Accuracy of "b>=



79/120

'altodextrin

7 1<%

@

1<

1@

%<

%@

2 $s

2-8),K:

2-S

O &NH*( e>

S-2-S

%"% %"< %== %=! %=$ %=

Binding 0nerg/ 8eH:

2$s

>"



80/120

Glass

iS%? organic surface

contaminants

%

$

!

=

1<

1%


81/120

Halence band


82/120

Polyethylene cross-lin0in,

θ

4 &EL

θ

4 CEL

Binding energ/ 8eH:

2 n t e n s i t / 8 a . u . :

Pol/eth/lene treated b/ lasma ischarge in nitrogen

2nfluence of angle of

hotoelectron collection cross-lin0in,

occurs at the outer surface

=%


83/120

=

XPS - Basic aspects

Photons and electrons

P elemental anal/sis (ith surface selectivit/

2nstrumental asects

3eatures of an P sectrum

core hotoelectron ea's and bac'ground #uger ea's

energ/ scale referencing

valence band

additional features

Illustration< Stre!tococcus t$ermo!$ilus

#dditional features


84/120

=$

2 n t e n s i t / 8 a

. u . :

-ra/ source #l,

monochromatiFed

atch

#uger vs hotoelectrons2nfluence of source

0' and 0b scales

ea' osition,

bac'ground

satellites

! !

-ra/ source +g,

not monochromatiFed

Source satellites #α(*@

#dditional features


85/120

=@

'ultiplet splittin,

Spin couplin,

bet(een unaired electron left in a core level

and

unaired electron in the outer shell number

multilication or broadening of P ea's of transition elements

ossible information on coordination

Sh 0 0

#dditional features


86/120

Sha0e-up pea0s

)ombination ofhotoe9ection of electron from atom

and

e7citation of valence electrons

discrete energ/ loss

satellite at higher 0b

Example: π $π transition of aromatic pol!mers

=!

Sh 0 0

#dditional features


87/120

Sha0e-up pea0s

2 $s of polystyrene

x 104

2

4

6

8

10

12

C P S

300 2"0 280

Binding Energy (eV)

2-8),K;

sha0e up

*oes not aear

if aromaticit/ is destro/ed b/ o7idation

as roduced b/ lasma surface o7idation

=>

Sha0e-up pea0s#dditional features


88/120

==

7 1<

@

1<

1@

%<

%@

<

@


89/120

JJ

J

S 1 s

S G L L

S

)

1

i % s

i %

7 1<$

<

@

1<

1@

%<

%@

<

S 1 s

S G L L

S

)

1 s

i % s

i %

7 1<$

<

%

$

!

=1<

1%

1$

1!

1=

1


90/120

"<

2 n t e n s i t / 8 a

. u . :

-ra/ source #l,

monochromatiFed

-ra/ source +g,

not monochromatiFed

"ner,y loss pea0s

*iscrete features

modulation

of the bac'ground steaffecting

all the ea's of the hase

Pea0 tails

#dditional features


91/120

Pea0 tails

2 $s of ,raphite

%"> %"$ %"1 %== %=@ %=%

Binding 0nerg/ 8eH:

2 n t e n s i t /

8 a . u . :

#ttributed to interactions

bet(een ositive core hole

and conduction electrons

2 $s of polymers containin, saturated hydrocarbon chains

e.g. ol/eth/lene

Hibrational fine structure hotoelectron energ/ loss

due to vibrational e7citation "1

Illustrati1e summary


92/120

"%

P sectrum of alumina

on (hich mol/bdenum

o7ide (as deosited

The intensit/ scale (as

changed b/ a factor .@

at 0b C $@< eH

Illustrati1e summary


93/120

XPS - Basic aspects

-ra/s and electrons

0ssence of P

2nstrument

3eatures of a P sectrum4uantification

from comle7 realit/ to ractice

arameters

aroaches

"

)omle7 realit/


94/120

Schematic representation

"$


95/120

)omle7 realit/


96/120

dAa

flux of photons

in direction

cross section of photoioni8ation

robabilit/ of emission of an

electron (hen a hoton hits the

element

factor of

anisotropy,

varies (ith γ,

deends on orbital

amount of element #

[ ] [ ] [ ] *a *a

;

*a * *a *a


97/120

dAa

[ ] [ ] [ ] *a *a

;

*a * *a *a


98/120

[ ] [ ] [ ] *a *a

;

*a * *a *a


99/120

[ ] [ ] [ ] *a *a

;

*a * *a *a


100/120

Assumption nL$

- surface lanar and homogeneous along 7 and /

- average values of 5, L #a, T #a 8little variation according to 7, /, , :

( ) z z C ’

R DT L J I Aa A Aa Aa Aa Aa Aa Aa d)$*(ex% 0 $S θ λ σ θ ∫ ∞

=

irradiated

areaaccounts for the difference

bet(een irradiated area

and area of collecting

hotoelectrons

roughness factor

For different elements of a ,i1en sample < * S* f:θ

;* R* are the same

use ratio of intensities IAa ) IBb

p ,

1


101/120

( ) z z C ’ R DT L J I Aa A Aa Aa Aa Aa Aa Aa d)$*(ex% 0

$S θ λ σ θ ∫ ∞

=

B Bb Bb Bb Bb

A Aa Aa

Bb

Aa

C T L

C T

I

I

λ σ

λ σ *a *a >= cos θ

cos θ

i 4 sensiti1ity factor

B Bb

A Aa

C iC i=

same for * et 7

1


102/120

Photoionisation cross section σ

. =. ScofieldKartree-later subshell hotoioniFation cross-sections at 1%@$ and 1$=> eH

5. 0lectron ectrosc. 6elat. Phenom. = 81">!: 1%"-1>

Anisotropy factor %

L #a C 1 ? O 8angle magique:

1


103/120

ransmission function of analy8er

*eends on instrument, on 0ass and on 0' often considered of the form

4 0 "p T"p ) "0Un 3ith E n $

Providing 0ass is the same for all ea' records

Aa ) Bb 4 T"0 Bb ) "0 AaUn

The value of n deends on the instrument.

The uncertaint/ on the value of n is lo(er if the ea's anal/Fedcorresond to close 0' values

07erimentall/ determined values T ma/ be rovided

b/ the sectrometer

manufacturer 1


104/120

Inelastic mean free path λ

0valuations of absolute values can be found or comuted 8literature:

*eends on 0' and on the matri7

1


105/120

λAa ) λBb 4 T"0 Aa ) "0 BbUm

*ifferent values of m reorted in the literatureR frequentl/ around .

2mact of uncertaint/ lo(

if the ea's anal/Fed corresond to close 0' values,

1


106/120

2onsiderin, the analy8ed 8one as homo,eneous

C most common ractice, using sensitivit/ factors Based on

assumtion 1

assumtion % intellectual contradiction

comosition of the surface la/er as seen b/ P V

106

5se of sensiti1ity factors3o 3ays

#roaches


107/120

"1aluated by first principles approach

"mpirical 1alues

*etermined (ith standards

guarantee regarding surface comosition

Tabulated values related to a given element

valid for one t/e of sectrometer Ex. )agner, ? #s ta"en as reference spectrometrer with n A #

3o 3ays

Bb Bb Bb Bb

Aa Aa Aa Aa

T L

T L

λσλσ

= Bb

Aa

i

inm

Bbk

Aak,

Bb

Aa

E

E −

÷÷

σσ

=

1

Sur1ey of approaches

#roaches


108/120

2onsiderin, the analy8ed 8one as homo,eneous

C most common ractice, using sensitivit/ factors Based on

assumtion 1

assumtion % intellectual contradiction

comosition of the surface la/er as seen b/ P V

Simulatin, data

on the basis of h/othetical models of the comle7 solid

often using data collected (ith several ta'e off angles θ - *ata C intensit/ ratios need of absolute values for arameters

- *ata C absolute intensities additional need to ta'e into accountdetails regarding -ra/ beam, hotelectron collection

as the samle is being tilted

See course 11 and 1,&

108

Analy8ed area 1ersus bombarded area

e X-ray e-

#roaches


109/120

X-ray e-

X-ray e- X-ray e- X ray e

Bombarded

area

Sld generation 2 1

ThetaAigma robe

Gratos #7is Ultra

H 0)#L#B %@<

50SL 5P-"


110/120

XPS - Basic aspects

-ra/s and electrons

0ssence of P

2nstrumental asects


4uantification

)hemical shift

11<

)hemical shift

"ffect of oxidation sta,e


111/120

1

Binding 0nerg/ 8eH:

SiESiI>

Si &p

θ C


112/120

11%

h i f t

h i f t


113/120

ol/8vin/l trifluoroacétate:

"ffect of electrone,ati1ity of surroundin, atoms

3ormal o7idation stage ) 1 -%

)% <

) ?

)$ ?113

"ffect of first and second nei,hbour

)hemical shift


114/120

ol/8trifluoroéth/lacr/late:

"ffect of first and second nei,hbour

3ormal o7idation stage

) 1 -%

)% -1

) -1

)$ ?

)@ ?

114

Selecti1ity to chemical functions

P l 8éth lZ té é ht l t :

)hemical shift


115/120

7 1<

@

1<

1@

%<

%@

<

@


116/120

@

1<

1<

%<

7 1<

%

@

1<

1@

%<

%@

<Poly :%-serine;

7 1<

%

%

$

!

=

1<

1%

1$

1! 7 1<

%

%

$

!=

1<

1%

1$1!

1=

7 1<

%

$

!

=

1<

1% 7 1<%

%<

<

$<

@<

!<

><

=< 7 1<=<

"<2olla,en

7 1<

=<

"<

1

@

1<

1@

%<

%@

<

@

%"% %"< %== %=! %=$ %=%Binding 0nerg/ 8eH:

2 n t e n s i t /

8 c o u n t s A s :

2-8),K:S-2-S

2-8),K:

2-8),K:

2-8),K:

)-/K%?

2-S

2-S

2-N

2-S

2-N?

2-N

SC2-S

SC2-N

SC2-S

SC2-S

SC2-N

)-/K

)-/K

)-/K

)-/K%?

6$/

)-K

C)-N

C)-N

P--

)-

S-)C

P--)

SC)--)

PC

/ $s

116

XPS Basic aspects


117/120

XPS - Basic aspects

-ra/s and electrons

0ssence of P

2nstrumental asects


4uantification

)hemical shift

Time line

11>

=istorical sur1ey of physical concepts

Time line


118/120

Source . /enet 11=

teinhardt 6, erfass 05. [X-ra/ Photoelectron Sectrometer$D$

ime line for XPSTime line


119/120

for chemical anal/sis\, *nal.&hem. 1"@1R &( 1@=@-1@"


120/120

1st P sectrometer in Belgium U)L X 5.5. 3riiat$C$

3irst commercial sectrometer 8Ke(lett Pac'ard X U#:$H

#ngle 6esolved P 8#6P:, elius et al.$CE

3irst -ra/ monochromator U. elius ] G. iegbahn$C&

+ultitechnique s/stems$CC

3ocused -ra/ beam and scanning imaging 8Q1@

Course I.a. XPS Basics

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Transcript of Course I.a. XPS Basics