Chemical analysis of surfaces and organic thin films

by means of SIMS

Secondary ion mass spectrometry (SIMS)

– Static SIMS (SSIMS) vs. dynamic SIMS –

Cu (111) surface 1 ps after the

bombardment with a Cu atom having

an energy of 5 keV.

(H.M. Urbassek: Molecular-dynamic

simulation of sputtering. Nuclear Instru-

ments and methods in Physics Research,

VOL B 122 (1997), S. 427-441)

1 2 3 4 6 8 10

10

10

10

10

10

10-1

-2

-3

-4

-5

-6

rel. yield

culster size (Ag)

experiment

n

Monte Carlo

moleculardynamis (500 ps)

moleculardynamic(nascent)

X+ + -

surface

ion gun

beam of primary ions

of the sample

desorbed neutral particle

desorbed anion

desorbed cation

shock wave

X+ + -

ion gun

desorbed

desorbed anion

desorbed cation

shock wave

SNMS

SIMS

SIMS

mass analyzer m/z

neutral particle

Quadruple secondary ion mass spectrometer

detector

alternating voltage

Sector field secondary ion mass spectrometer

detektorH

Secondary ion mass spectrometry (SIMS)

– Units to separate (molecule) ions of different masses –

Sector field secondary ion mass spectrometer

– NanoSIMS 50 (Cameca, Paris, France) –

Si- BSi-

silicon doped with boron,

line width 0,14 µm,

acquisition time: 16 min (ONERA, France)

sample

extractor

tube

+

reflector

detector

Ar ions

pulsed

22

kin t

s

2

mv

2m

E

+--

Ar+

U = 10 kV Ekin

+-0

+

J.C. Vickerman

Charles Evans

A. Benninghoven

Static secondary ion mass spectrometry (SSIMS)

– Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) –

Time-of-Flight Seconday Ion Mass Spectrometry (ToF-SIMS)

– Pulsed primary ion beam –

x/y deflector

lense

extraction unit

anode

gas inlet

ion source

90° deflector

focus

sample

lense

buncher deflector

buncher

puls length 59...1888 ps

sample deflector

2 2

kin t

s

2

m v

2 m

E

20 40 100 140 160 180 200

m/z [amu] 50 100 150 200

count rate

C 2 H 2 + SiO

+

C +

polystyrene fingerprint spectrum

C 2 H 3 +

C H 3 +

C H 2 +

C H 3 +

Si , + C 2 H 4

+

C 2 H 5 +

C 3 H 3 +

,

C 3 H 5 +

C 3 H 7 +

C 4 H 5 +

C 4 H 7 +

C 4 H 9 +

C 5 H 5 +

C 6 H 5 +

C 7 H 7 +

C 8 H 9 +

C 9 H 7 +

C H C H 2

Time-of-Flight Seconday Ion Mass Spectrometry (ToF-SIMS)

– Spectral information –

Time-of-Flight Seconday Ion Mass Spectrometry (ToF-SIMS)

– Excellent mass resolution – PTFE after its treatment in a hydrogen plasma –

69.0 81.0 119.0 .5 .6 .6

CF 3 + C 2 F 5

+ C 2 F 3 +

C 6 H 9 +

unmodified PTFE

69.0 81.0 119.0 .6 .6 .5 m/z [amu]

C 5 H 9 +

C 6 F 2 H 2 +

CF 3 + C 2 F 3

+ C 2 F 5 + C 6 H 9

+

C 5 H 7 N +

F

F

H H

H +

plasma-treated PTFE

m/z measured mm calculated mc = |mm-mc|

CF3+ 68.9873 68.9952 0.0079

C5H9+ 69.0695 69.0717 0.0022

C2F3+ 80.9888 80.9952 0.0064

C6H9+ 81.0645 81.0717 0.0072

C2F5+ 118.9858 118.9920 0.0062

C6H9F2+ 119.0659 119.0685 0.0026

All values were given in [amu]

Fragmentation mechanisms

– e.g. Polymers with aromatic units –

CH2 CH CH3

C CH2

103 amu

- H- H

- ethylene 27 amu

77 amu

39 amu

- ethylene

51 amu

- propylene (41 amu)

CH2 CH CH3

CH2 CH CH2

77 amu- phen- H

51 amu

39 amu- H2

128 amu

152 amu

178 amu

m/z [amu]60 80 100 120

Polystyren auf SilberAg107

Ag109 HC CH2

Cl

m/z [amu]500 700 900 1100

x 13

m = 14,014 amu (CH

HC CH2

+

Poly(4-chlorstyren)

-

2)

Fragmentation mechanisms

– e.g. Polymers with aromatic units –

Polystyrene on silver substrate

Poly(4-chloro styrene)

Analysis of additives in polymers

– No chance for XPS –

600 640 68060 180100 140 220 260 300

277233

m/z [amu]

637

HO

H3C

CH2 CH2 C

O

CH2CH2O CH2CH2 O C

O

CH2CH2 OH

CH3

O

Irganox 245

600 640 68060 180100 140 220

235

191

m/z [amu]

HO CH2 CH2 C

O

O CH2(CH2)4CH2 O C

O

CH2CH2 OH

Irganox 259

595

[M–H]-

[M–H]-

Analysis of additives, impurities, modifiers etc.

Application note of ToF-SIMS

– Grafting of styrene and maleic anhydride on polyolefin surfaces –

There are polystyrene sequences

[Sty-Sty-Sty] ?

There are maleic anhydride sequences

[MSA-MSA-MSA] ?

There are hydrolyzed maleic anhydride

groups?

C H 2 C H

O O O

H H C H 2 C H

+ monomers, + initiator

m/z [amu]160 180 200

147

152

161

165

203

205178

207

215

217233

150 170 190 210 220

152

165

178

205 C CH CH2C

207 C CH CH3CH

147 H2C CH2 CH2

C

O+

161 H2C CH2 CH2 CH2

C

O+

203 HC CH2

OO

CH2

CO

C

CH

215 HC C CH2 CH

CO

C

CH2

O O

217 CH CH2 CH

CO

C

CH2

O O

H2C

233 HC C CH2 CH CH2

C CO O

OH OH

20 m/z [amu]40 60 80

x 200 200 µm

15.02 amu 22.99 amu 29.04 amu 38.97 amu 62.94 amu 77.04 amu

281.08 amu197.00 amu91.06 amu

low count rate high count rate

50 µm

Imaging-ToF-SIMS

– Laterally structured poly(-benzyl glutamate) –

20 m/z [amu]40 60 80

x 200 200 µm

15.99 amu 26.02 amu 31.97 amu 32.98 amu 89.08 amu 89.12 amu

163.12 amu 196.96 amu 213.03 amu 394.01 amu 394.08 amu

Total ion image and linescan high count rate

Imaging-ToF-SIMS

– Laterally structured poly(-benzyl glutamate) –

Summary

SSIMS [ToF-SIMS]

SSIMS is a method oriented to detect and analyse molecules on the surface of samples

analysis of molecule species [chemical structure and mass of the polymer's repeating units

type of monomer

non-quantitative surface analysis [semi-quantitative surface analysis],

analysis of end groups Endgruppen determination of molar masses and molar mass

distributions on surfaces

analysis of additives, impurities, modifiers etc. [traces can be detected],

analysis of structural changes caused by surface mofication, functionalization, and aging.