Analytical Capabilities of a Pulsed RF Glow Discharge Plasma Source with GD-OES

Analytical Capabilities of a Pulsed RF Glow
Discharge Plasma Source with GD-OES

Celia OLIVERO
Applications GD-OES lab manager
Celia.olivero@horiba.com
Horiba Jobin Yvon 16-18 rue du canal
91165 Longjumeau Cedex, France

© 2012 HORIBA Scientific. All rights reserved.

Introduction to the Technique


History and Context
 The analytical Glow Discharge Optical Emission Spectrometry was invented
in Europe by researchers from the Steel Industry
 For many years it has been primarily applied to the metal industry
 The developments made in the last 12 years (RF, pulsed RF, pulsed RF with
automatic matching) have drastically changed the situation
 Pulsed RF GD-OES is now a flexible tool for thin and thick films analysis of
conductive/non conductive materials
 In parallel the EU project coordinated by HJY (www.emdpa.eu) has led to
the development of the Plasma Profiling TOFMS™ that couples the same
pulsed RF plasma source to a Time of Flight Mass Spectrometer and offers
complementary possibilities
 We will present today the analytical capabilities of GD-OES


GD: Principle of Glow Discharge
 When the voltage
 Low pressure gas increases the cell
begins to glow and the
 2 electrodes cathode is sputtered.
 Power supply  The glow is not uniform.
 Physical separation of
sputtering (near
cathode) and excitation
zone (near anode)


View of the HJY GD « source »

External sample mounting
Sample is the cathode
Pulsed RF power: Conductive and non
conductive materials
Control of crater shape: atomic layer by
atomic layer


Source Design principle

windo
w
vacuum Ar

λ

4mm crater
Anode
Vacuum

R Sample
F
Cooling


Pulsed RF source

 Both conductive and non conductive samples
and layers
 Stable signals from the start: Surface! analysis
 Simple: one source optimized
 One calibration for composites (bulk and layered
samples, conductive and non)
0.9

0.8

0.7

0.6
P
0.5 S
Si
0.4 Ni
Cr
0.3

0.2

0.1

0.0
2

5

2

2

9

1
:25

:01

:28

:54
:0

:2

:0

:3

:4

:5
09

09

11

11

14
08

10

10

11

13


Pulsed RF: details
RF Pulsed Source -Short duration (30 μs to 1 ms)
- Various repetition rates (duty cycles)
- Possibility to use high instantaneous
powers (> 60 W) for sensitivity
-Possibility to use soft conditions for
plasma cleaning
- Ph. Belenguer, et al. Spectrochim. Acta B 64, 7 (2009) 623-641.

Main Advantages for OES: Example: PVD deposition of
- Low average power magnetic layer on PET
(analysis of heat-sensitive
materials)
- Tunable (Slower) sputtering
rate
- Control on the crater shape
- Improved depth resolution


Light Collection and Simultaneous analysis
(polychromator)

High Dynamic Detector

Rowland circle Secondary slit

Sample
Lens

Grating Primary slit

Spectrometer Source


Flexibility of the monochromator

 N+1 element in depth
profile
 Measurement of
additional elements
for bulk
 Spectrum acquisition


Monochromator: spectrum of a sample and
comparison to libraries


HJY GD-OES: GD-Profiler2

Sample position

Spectral range from H
121nm to K 766nm
All elements of periodic
table

Targets of materials characterization

Bulk Analysis Depth Profiling

Fe
Weight % Cr Ni

Px5
N
Cr

Depth (Micrometers)


Main features
Characteristics of pulsed RF GD-OES instruments
 All elements of periodic table

 Fast sputtering (15-150nm/s)

 Depth Profile and Bulk

 Thin and thick films

 Atomic information

 No isotopic information except for deuterium

 Excellent depth resolution


What materials?
 Conductive and non conductive
 Solid materials (resistant to few bars locally)
 Bulk
 Coated: single or multi
 Flat on analysis surface (curved surface
possible with special accessory use)
 Min size: > 3mm
 Typical analysis surface: over 4mm diameter


What Questions are answered by rf GDS?

 What elements are present in the sample?
 At what concentration levels?
 Is the sample homogeneous in depth?
 Were any coatings or surface treatments applied to the sample?
 Where is this surface defect coming from?
 How many coatings have been applied?
 How thick are the coatings? What is the coating weight?
 What are the competitors doing ?
 Is there any contamination at the interface?
 Any oxidation or corrosion of the sample? How this material reacts
to corrosion?
 Any diffusion in the coatings?

 GD will tell within seconds to minutes !


Typical result:
Complex multilayer coating (quali)

Distribution of the
elements as function of
time (depth) =>
qualitative

Multilayer TiN/TiAlN on Stainless steel

Same quantified (in At%)


Quantification basis

 GD is a comparative technique.
 Calibration needed.
 Calibration in GD can be done using a
multimatrix approach correcting for
Sputtering Rate.

 The GD sputtering efficiency is sample
dependant.
 Depth Profile: Sputtering rate usually
changes with the depth.


Quantification: Simple

ci q M = k i I i
where The measured
intensity for a
– ci composition given element is
– qM sputtering rate proportional to its
concentration in
– Ii intensity the plasma
– ki constant


Sputter Rate Correction
Multimatrices Calibration for Cr
Aluminum Base
SR 0.1 Iron / Steel Bases
SR 0.4
Sputter Rate
Concentration %

Zinc Base
SR 1.2

Lead Base
SR 2.0
10% Cr

IAl IFe IZn IPb Light Intensity


Aluminum Base
Which Concentration of Cr should give
SR 0.1 Iron / Steel Bases
the same light in a material having a SR 0.4
SR = 1?
Concentration %

Virtual Base
SR 1
Apply Sputter Rate
Correction to this point Zinc Base
SR 1.2

Conc. X SR Lead Base
SR 2.0
10% Cr

IAl IFe IZn IPb Light Intensity


SR X

Only ONEof Unknown Sample
Analysis Cr Calibration Curve
Concentration %

Valid for Multimatrices Virtual Base
SR 1

Virtual Cr
Concentration

Light Intensity
IX

Analysis of Unknown Sample
Fe Cr Ni Mn
Virtual
Virtual Cr %
Virtual Virtual
Fe % Ni % Mn %
I Fe I Cr I Ni I Mn
Virtual Concentration
Fe . SR 50 % Fe . SR + Cr . SR + Ni . SR + Mn . SR = 75 %
Cr . SR 10 %
Ni . SR 10 % All the elements within the unknown
Mn . SR 5 % sample have the SAME SR
Total (Conc. X SR) = 75 %
Real Concentration (Fe + Cr + Ni + Mn) . SR = 75 %
Fe = 50 % / 0.75 = 66.67 %
SR = 75 % / (Fe + Cr + Ni + Mn)
Cr = 10 % / 0.75 = 13.33 %
Ni = 10 % / 0.75 = 13.33 % Sum of Concentration = 100 %
Mn = 5 % / 0.75 = 6.67 % Sum Normalization
Total (True Conc.) = 100 % SR = 75 / 100 = 0.75

Illustration: Calibration for bulk.
Mo in stainless steels with 2mm anode


Calibration for depth profiling.
Multimatrix calibration


Applications


Bulk: precious metal samples with GD spots

Control of Product quality

Bulk: precious metal LOD


Some applications in automotive

Application Description
Base metals Chemical composition of all metals and alloys (Fe, Al, Zn,
Mg ..)
Li batteries Control of electrodes
Ceramic coatings Engine antiwear coatings *
Zn coatings All Zn coatings can be characterised (ISO norm)
Thermal treatments Nitruration, etc
Organic coatings (Bonazinc Composition and behaviour of the coatings *
etc)
Phosphatations Control of phosphatations
DLC coatings Hard coatings used for instances in Formula 1
Corrosion studies Identification of defects, studies of new processes *
Cataphoresis Control of cataphoresis bathes and coatings *
Glasses UV protection coatings on glasses *
Benchmarking Comparative study of all parts of competitive cars *
Plastics Coatings on plastics *
Electronic parts Control of suppliers, defects
Painted car bodies In depth analysis of a car body down to 200 microns *
* indicates presence of non conductive layers. They count for more than 50% of the work done in an automotive
laboratory.


GD : Help for industry and for research

 Selection of right material for application
 Control of preadjustment of surface before process
 Selection and control of right nitriding parameters
 GD complementary to other surface techniques
 Speed of analysis is crucial for multiparametric research


Thick coatings:Thermal treatment on steel


Depth Profile: Carbonizing and nitriding steel

100

80 Fe
Carbonizing
Concentration / at%
and nitriding 60

40
C(× 3) Ni
Steel
20
N(× 2)
0 1 2 3
Depth / um


Nitro-carburizing
Overlay Good / Bad Process
N
Weight %

Fe
Fe Fe
Bad

N N
C N x 10
Good
C x 10
Fe
N
N C
N
C
C

Depth (Micrometers)


Paint on car (1)


Paint (zoom)


Paint quantified


Applications: typical interests in coated material

Composition
Composition (%)

100
40

60

80
20
0
Protective coating

0.0
Native oxide (few nm) 10-100 nm

0.5
Corrosion protection
Tribological improvement

1.0

Depth
Depth µm)
1.5
Complex coating

(
2.0
Structure: Multilayer, Gradient,..
10-1000 nm
Elemental Composition

2.5
Interface details

3.0
Layer Intermixing
Compound formation

3.5
100 nm
Intermediate layer
Adhesion improvement
Element Inter-diffusion
Substrate protection 1 mm

Substrate
Element Inter-diffusion

39

Ionic implantation
Implanted sample

Disorganized region Crystaline region
“Oxide” Atoms implanted Metallic atoms

Courtesy of AIN Spain


Successive implantation of C and N

100

90

80 Fe
70
N
60
% At

50

40
C
30 Cr

20

10

0
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6

Profundidad (µm)

Courtesy of AIN Spain


Thin layers. PVD coating. 107 layers 20nm CrN/TiN
Overlap of 2 measurements


Multilayers: depth resolution issue

 Mirror for X ray
Alternance Mo/B4C/Si
60 periods 60 periods

Each layer (Mo or Si) is Substrate
6.97nm thick

Sample used for a RR experiment prepared by
Prof. Tolstoguzov on depth resolution (by SIMS
mainly). OES results presented at the SIMS 2011
conference


Qualitative profile


Zoom on qualitative profile


Example on thin Anodised Al
(nm)

120 3% B
Cr

240
bubbles

Al substrate


Speed of analysis
10

Cr

8
Note the Cr
peak Al
Intensity (V)

6
B

4 O
O*7

2
H
P Cu

0
0 5 10 15
Time (s)

Thin anodised Al analysis


Analysis Time issue

(a) SIMS (b) GD-OES
Vacuum time : Vacuum time:
1hour No
Analysis time: Analysis time:
3 hours 15 seconds
Total Time:
4 hours

Surface of 150 nm Al2O3 film (with a Cr marker of ~ 2nm) formed on highly
flat Al by anodic oxidation

Analysis by (a) SIMS and (b) GD-OES.

Shimizu et al. Spectrochimica Acta B 58 (2003) 1573-1583

48 /14

Surface issue: Electrolytic Cu plate

Surface contamination by
rinsing water


Rf GD for surface studies
•Sample preparation
Mirror-finished, high purity aluminium,
electropolished in perchloric acid-ethanol
bath, then rinsed. Post-electropolishing
immersion treatment in a chromic acid-
phosphoric acid solution to remove the
thin Cl- doped surface film remaining after
electropolishing. Finally, the specimen
was rinsed in distilled water and warm air-
dried. A new hydrated oxide surface,
about 4 nm thick, is developed on the
surface after the previous treatments.
•Result description
The rf GD-OES depth profile shows the
oxide was hydrated throughout, in
agreement with XPS studies. However, in
addition, rf GD-OES shows copper
enrichment in the aluminium just below
the oxide.


Sub nm resolution. Adsorbed molecule


Sub nm resolution (BTA benzotriazole)


Pulsed operation with synchronized acquisition
RF
RF 75 µs
40 W
No pulse 5 W Pulse
time time
0.6 ms


Cationic exchange

Deep Craters in
Thick Glass

Over 80 µm, Flat Crater


Coatings on Glass
Repro: 2
measurements
overlaid

New pulsed
RF source


Importance of Pulsed Operation for Coatings on Glass

Precise
measurements of
major and traces (for
instances Na). No
diffusion induced
during
measurement.


CIGS: Quantified Depth Profile


Lower sputtering rate in pulsed mode

normal pulsed

→ Electric coating (CrO) on Steel ： 100 nm. In pulse mode, a C peak
in the CrO layer is detected. This peak is also seen in XPS.


Double layer of polymers

Follow up
of C, H,
molecular
band CH
and
elements
(here Cu)


Thick Organic Layers
Access to Embedded Interfaces

Patent filed
105 µm organic layer
sputtered in 12 min !
Flat crater
No chemicals !

Applications: PV
(measurement of
encapsulated cells),
DVD profiles…


Coated polymer films: multilayered InOx/Ag


GD as Cleaning tool


Rf GD as sample preparation technique
for microscopy

 Plasma sputtering. Plasma density (1014cm-3)
 Low energy of the Ar ions in GD : 50eV =>
nearly no surface damage
 No surface charge with RF
 No priviledged direction of the incident ions
onto the surface
 Use for SEM: no chemicals use
 Turn preferential sputtering into an advantage


Sample
Preparation for
SEM/TEM


Stainless steel, mirror polished
SEM view : part of GD spot inside


Zoom on crater bottom:
constrasts shows all
different phases

GD-OES for EBSD (Electron Backscatter Diffraction)

EBSD is an analysis technique that measures
crystal information near sample surface (at the
order of a few tens of nm). Therefore sample
surface condition of the area of interest is a very
important factor. A sample surface needs to be
clean and flat to do EBSD analysis.
Grain A Electron beam
× No good EBSD result can be obtained from a
insufficiently prepared sample surface
Sample surface
Grain B
EBSP
○ Electron beam

Sample surface
Grain A Grain B
EBSP


Complementary technique


GD and SEM
500

400
100% 100% 100%
x% y% z%

Intensity (V)
X
Cr
Cr Y
Ti
Ti Z
Cr
Cr 300

200
0.5 µm 0.5 µm 0.5 µm
100

100% 0
Substrate
Si 0 2 4 6 8 10 12 14
Si
Sputtering time (s)
Concentration (%)

Quantification

Depth (µm)


Raman microanalysis within a GD crater
Laser : λ = 514nm P=0,8mW

CrIII peak
Laser


High temperature oxides
Comparison SNMS/GD

Courtesy FZJulich


Recent researches conducted in GD OES
 CIGS solar cells characterisation
 Interactions plasma/surfaces
 RF GD plasma characterisation through modelling and electrical
measurements
 Use of GD plasma for Scanning Electron Microscope
 D analysis and control of H migration through D investigation in various
high temperature oxides
 Pulsed plasma nitriding control
 Instrumentation development: RF coupling improvement on non
conductors
 Li batteries (special device developed)
 Cr speciation with GD OES (ratios Cr/O)
 Fuel Cells control

 These researches have been done within phD thesis or are part of
advanced works in major industries; They are not exhaustive but only
here to give an idea of the variety of possible applications of GD.


More info on GD

Recent Books
Marcus:
“Glow Discharge Plasmas in Analytical
Spectrometry”
Wiley, November 2002

Nelis and Payling:
“Practical Guide to Glow Discharge
Optical Emission Spectroscopy”
Royal Society of Chemistry, Cambridge, 2003

Web
www.emdpa.eu
www.glow-discharge.com


Conclusions
 Pulsed RF GD OES is an analytical technique with many
potentials
 Fast analysis : We will be pleased to run some samples for you
free of charge under non disclosure agreement if required and
evaluate the potential of the techique for your research
 Large samples needed (about 2*2cm)
 Complementarity to other techniques
 Feel free to contact us

 celia.olivero@horiba.com
 patrick.chapon@horiba.com

Contact in Brazil: Philippe.ayasse@horiba.com
HORIBA Scientific
HORIBA BRASIL
Av. das Naçoes Unidas 21735 Jarubatuba 04795-100 Sao Paulo SP-Brasil
Tel. +55 11 5545-1595 Fax +55 11 5545-1570 Mobile +55 11 9458 3205


Analytical Capabilities of a Pulsed RF Glow Discharge Plasma Source with GD-OES

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