(low pressure reactive / dusty plasmas)plasmasfroids.cnrs.fr/img/pdf/cpi_kovacevic.pdf · e....

E. Kovacevic, GREMI Orléans, 08.07.2010

Mass spectroscopy(low pressure reactive / dusty plasmas)

E. Kovacevic


Outline

1. Introduction : method and devices

2. What can mass spectrosopy tell us about:

a) plasma chemistry

b) plasma response to the formation of the nanoparticles

3. Some other possibilities – TIMS, MBMS…

4. Conclusions, useful links and hints


Introduction

• An old method: 1st idea 1886, E. Goldstein, 1st experiment 1899 W.

Wien, 1st mass spectrometer J. J. Thompson

• charged particle passing through a magnetic field -deflected along a circular path on a radius proportional to the mass to charge ratio, m/e.

• steps: ionization-acceleration-separation-detection

Replica of J.J. Thompson's third mass spectrometer.


Mass spectrometers

1. Ion Source (electron or chemical ionization)

2. Mass Analyzer

ions are sorted and separated according to their mass to charge ratio.

3. Detector

Types:1. By ionization: MALDI (Matrix Assisted Laser Desorption/Ionisation); ICP-MS, glow

discharge,field desorption(FD), fast atom bombardment (FAB), thermospray,

atmospherical pressure chemical ionization (APCI), secondary ion mass spectrometry

(SIMS),spark ionization, thermal ionization …

2. By mass analyzer (either static or dynamic fields, and magnetic or electric fields):

sector field , time of flight, quadrupole, quadrupol ion trap, Fourier transform ion

cyclotron resonance…

3. By detector: electron mulitiplier, Faraday cups, ion-to-photon detectors, microchanel

plate detectors…


Introduction: common type ms

Example: Balzers PPM 420,

Manual, Günther Peter


Some important parameters

m/z= a.m.u. (in some other fields- Dalthons)

Analysers characteristics:

• Mass resolving power: resolution

ability to distinguish two peaks of slightly different m/z.

• Mass accuracy

the ratio of the m/z measurement error to the true m/z (ppm or milli mass units)

• Mass range

the range of m/z amenable to analysis by a given analyzer

• Linear dynamic range

range over which ion signal is linear with analyte concentration.

• Speed

the time frame of the experiment, the number of spectra per unit time

Cracking pattern!!!!!!!


Experimental set-up

Positioning:

sideway,

through the electrode,

ex-situ( gas extraction)…

Laser light scattering by the dust


Plasma chemistry: neutralsions source on

24 25 26 27 28 29

0

2000

4000

6000

plasma on

plasma off

Co

unts

(s)

m/e

0 10 20 30 40 50 60

100

1000

10000

plasma on

plasma off

Counts

(s)

m/e

Overview mass spectra

0 20 40 60 80

102

103

104

105

cp

s

Time (s)

5 W

16 W

32 W

64 W

mass 26- acetylene

Time resolved behavior of

acetylen precursor

(acetylen depletion)

(all examples for: C2H2:Ar= 8:0.5 sccm, p=0.1mbar, P=5-64W, RF CCP)


Plasma chemistry: neutrals

(ion source on)

0 40 80 120 160

1000000

H2C

2H

2

dust formation

plasma on

co

un

ts / s

t / s

100000

1000000

0 5 10 15 20 25 30 35 400

1x105

2x105

3x105

4x105

5x105

6x105

7x105

8x105

9x105

0.0

2.0x104

4.0x104

6.0x104

8.0x104

1.0x105

1.2x105

1.4x105

mass 4

0 c

ps

Time (s)

16W

26

40

mass 2

6 cps

Temporal behavior for:

precursor (26) and carrier gas (40)

Temporal behavior for:

precursor (26) vs product (H2; 2)

Berndt et al. Contributions to Plasma Physics, 2009 (rev)


0 40 80 120 160

10000

100000

co

un

ts / s

t / s

mass 50 (C4H

2)

The ignition of the plasma leads to

the formation of larger molecules as

for example C4H2 (mass 50).

Plasma chemistry: neutrals

ion source on

1.0 1.5 2.0 2.5 3.0 3.5 4.00.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4 mass 50

mass 78

CO

UN

TR

AT

E (

no

rma

lize

d)

Messung

The production rate of these

molecules is also affected by

the formation of dust particles.


Positive ions

ions source off!!!

0 25 50 75 100 125 150

0

2500

5000

7500

10000

12500

15000

17500

C10

H4

+

C8H

4

+

C6H

5

+

C6H

4

+

C6H

2

+

C4H

3

+

C4H

2

+

ArH+

Ar+

C2H

2

+

Co

unts

/sec

m/e

0 10 20 30 40 50 60 70 80 90 100

102

103

104

0 10 20 30 40 50 60 70 80 90 100

102

103

104

105

cps (

for

nitro

ge

n b

uffer)

Argon as buffer

cps (

for

arg

on b

uffe

r)

mass (m/e)

Nitrogen as buffer

Argon-acetylene plasma Nitrogen-acetylene plasma

(same conditions)

Kovacevic et al 2009, J.Appl.Phys.


Negative ions

• Positive ions - accelerated by the sheath field

(orifice floating, grounded, negative bias –last one can disturb plasma)

• Negative ions - confined in the bulk

extraction complicated!

• In DC glow discharges – simple

extraction through an orifice in the anode (see literature)

• In RF discharges sheath must be (locally) cancelled

Experimental tricks:

1. positively biased extraction orifice (disturbs plasma)

2. pulsed plasma, detection in the afterglow

See e.g. E. Stoeffels et al. J. Vac. Sci & Technol.A 5,2109, (2001) , Hollenstein et al. J. of Vac.Sci.&Technol.A-

14, 535, (1996), J. Meichsner et al. Contrib. Plas. Phys. 25, 503 (1985), Leukens, A. 1998, Doctoral Thesis,

L Overzet et al. Jpn. J. Appl. Phys. 36, 2443 (1997) …


Plasma answer to the dust particle formation

0 10 20 30 40 50 60 70 80

0.00

0.02

0.04

0.06

0.08

0

1

2

3

4

5 FTIR Scattering, 5000cm

-1

Abso

rba

nce

Time/min

Ar plasma on

off

C2H

2 added

dust forms!dust forms!

Elektron density

Ele

ctr

on

de

nsity/ cm

-3 x

10

9

off

dust forms!

Time resolved behavior of

scatter IR and electron density

0 200 400 600 800 1000 1200 1400 1600 1800

103

104

105

cp

s

time (s)

C2H

2 (26) neutrals

Time resolved behavior of the neutrals:

mass 26 (acetylen)

Dust particles change the plasma characteristics

20 40

0.00

0.02

0.04

0.06

0.08

0.10

Abso

rba

nce

/a.u

.

Time/min.

20 40

0

10000

20000

30000

40000

50000

60000

Cou

nts

/s

ions (40)scattering


Plasma answer to the dust particle formation* ion source off!

20 30 40 50 60 704.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

me

an

ene

rgy

t / min.

0 4 8 12 16 20

0,0

5,0x105

1,0x106

1,5x106

2,0x106

2,5x106

Ar plasma 52s after C

2H

2 admixture

dust, 5 min after acetylene admixture

Ion flu

x/c

ps

energy/eV

Energy spectra : fast escaping ions Energy spectra: time developement

∫ ∫ dEEfdEEEf )(/)(

Max= dust free

Ref: Kovacevic et al, Berndt et al 2003,2009; Stefanović et al NJP2003,PPCF2005; Denysenko et al Phys Plas. 2006, Hippler et al J. Phys D2007


10 15 20 25 30 35 40 45 50

1

10

100

1000

10000 N2-->N

2

+-->N

++NN-->N

+

Counts

/sec

Electron Energy (eV)

IBackground

IPlasma ON

IPlasma OFF

1. Threshold:

Ionisation of N-atoms

N + e-→→→→ N+ +2 e-

2. Threshold:

Dissociative ionisation of N2

N2 + e-→→→→ N+ + N + 2 e-

TIMS

Threshold Ionisation Mass-Spectroscopy: radicals, metastables

D.Douai, J. Berndt, J. Winter , J. Appl. Phys. 2002Example:HIDEN HALPSM 300


MBMS

Modulated Beam Mass-Spectroscopy: radicals, metastables

0 10000 20000 30000 40000 50000 60000 70000 80000

3400

3600

3800

4000

4200

4400

4600

4800

5000

Beam component

Chopper ein

cou

nts

/ s

t/ms

nbackground

Beam component

background component

Ionisation chamber

D.Douai, J. Berndt, J. Winter , J. Appl. Phys. 2002

P1

P2P3

Example:HIDEN HALPSM 300


Impurities

Spectrum can be contaminated in

different ways, e.g. by the oil from the

vacuum pump

For more see e.g.

John F. O’Hanlon, “A User’s Guide to

Vacuum Technology,” John Wiley &

Sons, New York, 1989.0 20 40 60 80 100

0

200

400

600

800

1000

1200

1400

1600

H20

+

Coun

ts/s

ec.

Time/min.

Water (impurities): from discharge

chamer, from mass spectrometer


Conclusions• Powerful tool for the dusty plasma analysis:

Plasma chemistry+plasma response to the formation of dust particles

• Not a straightforward method

Literature, links:• http://www.massbank.jp, NIST webbook.org

• http://www.dmoz.org/Science/Chemistry/Analytical/Mass_Spectrometry/

• http://library.med.utah.edu/masspec/elcomp.htm

• http://www.dmoz.org/Science/Chemistry/Analytical/Mass_Spectrometry/

• HMDSO: e.g. Magni et al.2001, J. Phys. D: Appl. Phys 34 87

• SiH4: e.g. C Hollenstein et al 1994 Plasma Sources Sci. Technol. 3 278

• Effects of positioning: works of S. Radovanov (NIST group)

• Acknowledgments:

J. Berndt, I. Stefanovic, D. Douai, J.Winter, L. Boufendi, Ch. Hollenstein, E&W Stoffels

Balzers (Infineon ag), HIDEN, SIMION


http://simion.com/

Calculation of fields

and ion trajectories

(low pressure reactive / dusty plasmas)plasmasfroids.cnrs.fr/img/pdf/cpi_kovacevic.pdf · e....

Documents