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E. Kovacevic, GREMI Orléans, 08.07.2010
Mass spectroscopy(low pressure reactive / dusty plasmas)
E. Kovacevic
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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.
E. Kovacevic, GREMI Orléans, 08.07.2010
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…
E. Kovacevic, GREMI Orléans, 08.07.2010
Introduction: common type ms
Example: Balzers PPM 420,
Manual, Günther Peter
E. Kovacevic, GREMI Orléans, 08.07.2010
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!!!!!!!
E. Kovacevic, GREMI Orléans, 08.07.2010
Experimental set-up
Positioning:
sideway,
through the electrode,
ex-situ( gas extraction)…
Laser light scattering by the dust
E. Kovacevic, GREMI Orléans, 08.07.2010
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)
E. Kovacevic, GREMI Orléans, 08.07.2010
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)
E. Kovacevic, GREMI Orléans, 08.07.2010
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.
E. Kovacevic, GREMI Orléans, 08.07.2010
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.
E. Kovacevic, GREMI Orléans, 08.07.2010
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) …
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
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
E. Kovacevic, GREMI Orléans, 08.07.2010
http://simion.com/
Calculation of fields
and ion trajectories