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

© 2012 HORIBA Scientific. All rights reserved.

Analytical Capabilities of a Pulsed RF Glow

Discharge Plasma Source with GD-OES

Celia OLIVEROApplications GD-OES lab manager

[email protected] Jobin Yvon 16-18 rue du canal

91165 Longjumeau Cedex, France

© 2012 HORIBA Scientific. All rights reserved.© 2012 HORIBA Jobin Yvon. 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

Low pressure gas 2 electrodes Power supply

When the voltage increases the cell begins to glow and the cathode is sputtered.

The glow is not uniform. Physical separation of

sputtering (near cathode) and excitation zone (near anode)


External sample mounting

Sample is the cathode

Pulsed RF power: Conductive and non conductive materials

Control of crater shape: atomic layer by atomic layer

View of the HJY GD « source »


Arvacuum

Vacuum

window

Cooling

Anode

SampleRF

λ

Source Design principle

4mm crater


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)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

08:25

09:02

09:25

10:01

10:28

11:02

11:32

11:54

13:49

14:51

P

S

Si

Ni

Cr


RF Pulsed Source

Pulsed RF: details

-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

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

- Ph. Belenguer, et al. Spectrochim. Acta B 64, 7 (2009) 623-641.

Example: PVD deposition of magnetic layer on PET


Light Collection and Simultaneous analysis

(polychromator)

Source

Lens

Primary slitGrating

Secondary slit

High Dynamic Detector

Rowland circle

Sample

Spectrometer


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

Spectral range from H 121nm to K 766nm

All elements of periodic table

Sample position


Depth ProfilingBulk Analysis

Wei

ght

%

Depth (Micrometers)

Cr

Cr

Ni

N

P x 5

Fe

Targets of materials characterization


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)

Multilayer TiN/TiAlN on Stainless steel

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


Same quantified (in At%)


Quantification basis

GD is a comparative technique. Calibration needed. Calibration in GD can be done using amultimatrix approach correcting forSputtering Rate.

The GD sputtering efficiency is sampledependant. Depth Profile: Sputtering rate usuallychanges with the depth.


Quantification: Simple

iiMi Ikqc

where

– ci composition

– qM sputtering rate

– Ii intensity

– ki constant

The measured intensity for a

given element is proportional to its concentration in

the plasma


Sputter Rate Correction

Co

nce

ntr

atio

n %

Aluminum BaseIron / Steel Bases

Zinc Base

Lead Base

Light Intensity

10% Cr

SR 0.1SR 0.4

SR 1.2

SR 2.0

Multimatrices Calibration for Cr

IAl IFe IZn IPb

Sputter RateSputter Rate



Co

nce

ntr

atio

n %

Aluminum BaseIron / Steel Bases

Zinc Base

Lead Base

Light Intensity

10% Cr

SR 0.1SR 0.4

SR 1.2

SR 2.0


IAl IFe IZn IPb

Virtual BaseSR 1

Which Concentration of Cr should give the same light in a material having a

SR = 1?

Apply Sputter Rate Correction to this point

Conc. X SR

Which Concentration of Cr should give the same light in a material having a

SR = 1?

Apply Sputter Rate Correction to this point

Conc. X SR



Co

nce

ntr

atio

n %

Light Intensity


Virtual BaseSR 1

X S

R

Only ONE Cr Calibration Curve Valid for Multimatrices

Analysis of Unknown Sample

I X

Virtual Cr Concentration


Sputter Rate CorrectionAnalysis of Unknown Sample

Fe Cr Ni Mn

I Fe I Cr I Ni I Mn

Virtual Fe %

Virtual Cr %

Virtual Ni %

Virtual Mn %

Virtual ConcentrationFe . SR 50 %

Cr . SR 10 %

Ni . SR 10 %

Mn . SR 5 %

Fe . SR + Cr . SR + Ni . SR + Mn . SR

Total (Conc. X SR) = 75 %

= 75 %

(Fe + Cr + Ni + Mn) . SR = 75 %

All the elements within the unknown

sample have the SAME SR

SR = 75 % / (Fe + Cr + Ni + Mn)

Sum of Concentration = 100 %

SR = 75 / 100 = 0.75

Real ConcentrationFe = 50 % / 0.75 = 66.67 %

Cr = 10 % / 0.75 = 13.33 %

Ni = 10 % / 0.75 = 13.33 %

Mn = 5 % / 0.75 = 6.67 %

Total (True Conc.) = 100 %

Sum Normalization


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 etc)

Composition and behaviour of the coatings *

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


1 2 3

20

40

60

80

100

0

Depth / um

Con

cent

ratio

n / a

t%Fe

NiC(× 3)

N(× 2)

Steel

Carbonizing and nitriding

Depth Profile: Carbonizing and nitriding steel


Nitro-carburizingW

eig

ht

%

Depth (Micrometers)

Overlay Good / Bad Process

N x 10

C x 10

Fe

N

N N

N

Fe

C

C

CN

N

C

FeFe Bad

Good


Paint on car (1)


Paint (zoom)


Paint quantified


39

Protective coatingNative oxide (few nm)Corrosion protection

Tribological improvement

Complex coatingStructure: Multilayer, Gradient,..

Elemental Composition Interface details

Layer IntermixingCompound formation

Intermediate layerAdhesion improvementElement Inter-diffusion Substrate protection

SubstrateElement Inter-diffusion

10-1000 nm

100 nm

1 mm

10-100 nm

0.00.5

1.01.5

2.02.5

3.03.5

0 20 40 60 80

100

Composition (%)

Depth (m

)

Dep

th

Composition

Applications: typical interests in coated material


Metallic atoms “Oxide” Atoms implanted

Disorganized region

Implanted sample

Crystaline region

Ionic implantation

Courtesy of AIN Spain


0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,60

10

20

30

40

50

60

70

80

90

100

Cr

Fe

N

C

% A

t

Profundidad (m)

Successive implantation of C and N

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

Each layer (Mo or Si) is 6.97nm thick

Substrate

60 periods

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

Al substrate

240

(nm)

3% B

Cr

bubbles

120


Speed of analysis

O*7

0

2

4

6

8

10

0 5 10 15

Time (s)

Inte

ns

ity

(V

)

Cr

B

O

Al

PH

Cu

Note the Cr peak

Thin anodised Al analysis


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

SIMSVacuum time :

1hourAnalysis time:

3 hoursTotal Time:

4 hours

(a) (b) GD-OESVacuum time:

NoAnalysis time:

15 seconds

48 /14

Analysis Time issue


Surface issue: Electrolytic Cu plate

Surface contamination by rinsing water


Rf GD for surface studies•Sample preparationMirror-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 descriptionThe 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

PulseNo pulse

0.6 ms

75 µsRF

time

RF

time5 W

40 W


Deep Craters in

Thick Glass

Over 80 µm, Flat Crater

Cationic exchange


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


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

normalnormal pulsedpulsed

Lower sputtering rate in pulsed mode


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 craterNo 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)

Grain ASample surface

Grain B

Electron beam○

EBSP

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.No good EBSD result can be obtained from a insufficiently prepared sample surface

Grain A

Sample surfaceGrain B

Electron beam×

EBSP


Complementary technique




SubstrateSubstrate

XX YY ZZx% x% CrCr

y% y% TiTi

z% z% CrCr

SiSi

100% 100% CrCr

100% 100% TiTi

100% 100% CrCr

100% 100% SiSi

0.5 0.5 µmµm

0.5 0.5 µmµm

0.5 0.5 µmµm

Sputtering time (s)

Inte

nsi

ty (

V)

100

200

300

400

500

2 4 6 8 10 12

00

14

Depth (µm)Depth (µm)

Con

cen

trati

on

(%

)C

on

cen

trati

on

(%

)

QuantificationQuantification

GD and SEM


Laser

Laser : λ = 514nm P=0,8mW

CrIII peak

Raman microanalysis within a GD crater


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

Webwww.emdpa.euwww.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

[email protected] [email protected]

Contact in Brazil: [email protected] Scientific

HORIBA BRASILAv. 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


Thank you

© 2012 HORIBA Jobin Yvon. All rights reserved.

Technology

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