Transcript EELS analysis of carbon structures

EELS analysis of carbon
structures
Gergely Kovách
MTA MFA
Nanotube seminar
2005. 05. 09.
Electron spectroscopy
-EELS, electron energy loss is characteristical to the material
-XPS, binding energy of C1s (284.6eV, 285.4eV) core level
electron, energy loss of core level electron
Electron energy loss in solids
a – zero loss
d – surface plasmons
b – fonons
e – bulk plasmons
c – band transitions
f – inner shell absorption edge
Hybridization of C atoms
-Energy difference in hybridized orbitals
-Broadening of  bonds
-Also valid for amorphous structure
-Pre edge feature in C1s-2p absorption
1s-2p(*)
Core level absorption spectra of C
samples
DLC
Graphite
Evap. C
STEM at 100 kV
sp2/sp3 obtained from peak intensity
J. Yuan, Micron 515 (2000)
Polarization of 1s-2pz transition
Anisotropic response of 1s-2p dipole transition -> difficulties in quantitative analysis
sp2/sp3 ratio:
Plasmon energy shift
sp2/sp3 ratio:
using reference material
normalized intensity [cps]
1.4
1.2
1
(c) Ar bomb.
0.8
0.6
(b) He bomb.
0.4
0.2
(a)
Polycristalline
diamond
0
0
5
10
15
20
25
30
35
energy loss [eV]
40
45
50
55
60
sp2/sp3 ratio:
C1s binding energy
Own measurements
EELS of 500eV electrons
7000
6000
intensity [arb. unit]
5000
4000
Nanotube
3000
HOPG
2000
HOPG impl.
1000
0
0
10
20
30
Energy loss [eV]
40
50
60
References
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J. Robertson, Mat. Sci. and Eng. R 37 (2002) 129-281
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Milne, J. Koskinen Phys. Rev. B 48, 4777–4782 (1993) Phys. Rev. B 48, 4777 (1993)
R.F.Egerton, Electron Energy-Loss Spectroscopy in the Electron Microscope (1986)
J. Bruley, L.M. Brown and S.D. Berger. Inst. Phys. Conf. Ser. 78 (1985), p. 561.
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J. Yuan, L.M. Brown, Micron 31 (2000) 515
G. Kovach, H. Csorbai, G.Z. Radnoczi, et al., Mat. Sci. Forum 414-4: 127-132, 2003
Properties of high-density amorphous carbon films deposited by laser ablation
S. Rey et. al. Appl. Phys. A 71 433 (2000)
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http://prola.aps.org/abstract/PRB/v48/i7/p4777_1
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