EUV spectra from the NIST EBIT
Transcript of EUV spectra from the NIST EBIT
EUV spectra from the NIST EBIT
D. Kilbane and G. O’SullivanAtomic and Molecular Plasma Physics group, UCD, IrelandAtomic and Molecular Plasma Physics group, UCD, Ireland
J. D. Gillaspy, Yu. Ralchenko and J. ReaderNational Institute of Standards and Technology,
Gaithersburg, MD 20899, USA
The 17th ADAS WORKSHOP23 – 25 September 2012Château de Cadarache
Outline
Motivation
EBIT • Experimental set up• Collisional-radiative modeling of plasma
EUV SpectraGadolinium
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• Gadolinium• Dysprosium • Tungsten
‘Potential lowering’ of 4fn ions
Summary
Motivation
Atomic and Plasma Theory• Hf, Ta, W, Au ions
advance atomic / plasma codespredict trends in atomic structure
Next-Generation
Lithography
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ITER• Diagnostics of hot
plasmas in fusion devices
• Modeling of sources at 6.x nm
NIST Electron Beam Ion Trap (EBIT)
EBIT creates, traps and excites HCI
Electron beam• collides with, ionizes and excites atoms• monoenergetic, width ~60 eV• tuneable, 1 - 30 keV• radius ~30 µm• density ~1011 cm-3
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• density ~10 cm
Ions are trapped• radially by space charge• axially by electrodes and magnetic field
EUV radiation• from the ions is observed with a flat
field grazing incidence spectrometer
http://physics.nist.gov/ebitGillaspy Phys. Scr. T 71 99 (1997)Blagojević et al. Rev. Sci. Instrum. 76 083102 (2005)
Collisional-Radiative Modeling
Atomic Data –Flexible Atomic Code (FAC)
• Relativistic potential to solve the Dirac eqn (CI and QED):
energy levels, radiative decay rates,
CR model –NOMAD
• non-Maxwellian time-dependent CR plasma code
• ~103 levels/ion
All important physical processes in the EBIT plasma
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energy levels, radiative decay rates, radiative recombination cross sections
• e- ion collisions are treated with distorted wave/Coulomb Born-exchange approx:
electron impact excitation, de-excitation, ionization cross sections
Gu Can. J. Phys. 86 675 (2008)Ralchenko and Maron J. Quant. Spectrosc. Radiat. Transfer 71 609 (2001)
• ~103 levels/ion typically 6-8 ions several million transitionsruns in minutes
• one free parameter – charge exchange CX between ions and neutrals
EBIT Spectra of Gd
Ion IP (eV)Rb-like 936Kr-like 1100Br-like 1142Se-like 1189As-like 1233Ge-like 1320Ga-like 1369
0
2×104
0
2×104
2×104
Cou
nts
(AD
U)
0.974
1.047
1.120
RbRb
Kr
KrKr
Br
BrBr
Br
0
5×104
0
1×105
1×105
Cou
nts
(AD
U)
1.320
1.378
1.450
Ge
Ge
Ga
Ga Ga
Ga
Rb-like to Cu-like gadolinium ion spectra
Ga-like 1369Zn-like 1481Cu-like 1531
Kilbane et al. accepted Phys. Rev. A (2012)Rodrigues et al. At. Data Nucl. Data Tables 86 117 (2004)
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0
0
2×104
0
5×104
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Wavelength (nm)
0
5×104
Cou
nts
(AD
U)
1.170
1.242
1.278
Br
Se Se
Se
As
AsAs
0
0
2×105
0
2×105
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Wavelength (nm)
0
1×105
7 7.2 7.4 7.6 7.8 8
Cou
nts
(AD
U)
1.520
1.588
1.697
Cu
Zn
Ga
Cu
GaCu
Zn
EBIT Spectra of Gd
Ge-like Gd ion
CR database of singly + doubly excited 4s24p2, 4p4, 4s24d2, 4s4p3, 4s24p4d, 4s24p4f, 4s4p24d, 4s4p24f, 4s24p5l, 4s4p25l, 4s24p6l, 4s4p26l
Energy levels of all singly, doubly, triply and quadruply excited n=4 complex 0
2
4
6
8
Cou
nts
(104 A
DU
)
EXP: 1.320 keV
second order
As
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Kilbane et al. accepted Phys. Rev. A (2012)
and quadruply excited n=4 complex 4s4d3, 4s4f3, 4d4, 4f4 4p24d2, 4p24f2 and 4p24d4f
CR database is updated with new energies of the lowest levels
Excellent agreement between measured and simulated spectra e.g. Se, As, Ge-like
0
4 5 6 7 8 9 10 11 12 13 14 15 16 17Wavelength (nm)
0
0.5
1
1.5
2
2.5
Em
issi
vity
(ar
b.un
its)
TH: 1.28 keV
Se
Ge
As
GeAs
As
Se
Gadolinium Data Tables
59 new lines: 4s-4p , 4p-4d and 4d-4f transitions ranging from 6.630 nm to 17.279 nm (mostly E1)
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Kilbane et al. accepted Phys. Rev. A (2012)Suzuki et al. J. Phys. B 45 135002 (2012)
‘Forbidden lines’Kr-like (9.726 nm) (M2)4p6(4p4
+)0 – 4p54d(4p3+,4d+)2
Se-like (9.684 nm) (M2)4s24p4(4p2
+)2 – 4p34d(4p+,4d+)4
Se-like (7.826 nm) (M2)4s24p4(4p2
+)2– 4p34d((4p-,4p2
+)3/2,4d-)0
Spectra were calibrated with known lines of Ba, Xe, C and O ions – accuracy 0.003 nm
Cu-like linesNIST EBIT NIFS9.086 nm 9.091(2) nm7.527 nm 7.524(2) nm
Next-Generation EUV Lithography at 6.x nm4d-4f + 4p-4d UTAs
Intense emission due to overlap of many open 4d and 4f subshell ions
Churilov identified Gd and Tb in LPPs and spark discharges
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7
7
7
7
7(a)La
15+
Ce16+
Pr17+
Nd18+
Pm19+
Sm20+ 14
15
16(b)
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Churilov et al. Phys. Scr. 80 045303 (2009) Kilbane and O’Sullivan Phys. Rev. A 82 062504 (2010)
4 5 6 7 8 9 100
7
7
7
7
7
7
7
7
7Eu
21+
Gd22+
Tb23+
Dy24+
Ho25+
Er26+
Tm27+
Yb28+
Lu29+
Wavelength (nm)gA
(10
13 s
−1)
50 55 60 65 70 7510
11
12
13
Z
E(eV)
Spectra of Gd and Dy at 6.x nm
Ag-like4d104f – 4d94f26.7423, 6.7465, 6.7884 nm
Pd-like4d10 – 4d94f 6.7636 nm
Ag-like4d104f – 4d94f26.6437, 6.5967, 6.2587, 6.3125 nm
Pd-like4d10 – 4d94f 6.2778 nm
DysprosiumGadolinium
2468
0.609
5
10
150.684
5
10
150.720
10 0.800
Cou
nts
(10
AD
U)
32
4
6 0.588
4
6
8
100.607
Cou
nts
(10
AD
U)
310
Sugar et al. J. Opt. Soc. Am. B 10 799, 1321, 1977 (1993)
Rodrigues et al. At. Data Nucl. Data Tables 86 117 (2004)
Gd Ion IP (eV)
Ag-like 358
Pd-like 565
Rh-like 601
Note: Very low current ~5 mA at 0.609 keVAbsence of strong resonant transitions
Dy Ion IP (eV)
Ag-like 423
Pd-like 664
Rh-like 702
5
0.800
5
100.877
6.4 6.6 6.8 7 7.2 7.4 7.6 7.8Wavelength (nm)
5
10
15 0.913
Cou
nts
(10
AD
U)
2
4
6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8Wavelength (nm)
2
4
6
8
10 0.653
Cou
nts
(10
AD
U)
Spectra of W
W Ion IP (eV)
Ag-like 881.4
Pd-like 1132.2
Rh-like 1179.9
Ag-like 4d104f – 4d94f2
5.1457, 5.0895, 4.8729, 4.9403 nm
Pd-like 4d10 – 4d94f4.8948, 5.9852 nm
Rh-like 4d9 – 4d84f4.9856, 4.9785, 4.9938,
2
3
4 0.849
4
6
8
10 1.025
Cou
nts
(10
AD
U)
3
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Sugar et al. J. Opt. Soc. Am. B 10 799, 1321, 1977 (1993)
Kramida and Shirai At. Data Nucl. Data Tables 95 305 (2009)
Strong resonant transitions observed at lower beam energies in Pd-like ions
Note: Feature observed at ~4.5 nm at 1.03 and 1.15 keV at the Berlin EBIT is absent
Biedermann et al. Phys. Scr. T 92 85 (2001)
4.9856, 4.9785, 4.9938, 5.0265 nm
2
4
4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6Wavelength (nm)
2
4
6
8
10
121.137
Cou
nts
(10
AD
U)
‘Potential Lowering’ of 4fn ions
Metastable states
• Many low lying excited states of Ag-like ions are populated by collisions
• These metastable states remain well populated
• Beam energy required to 0
100
200
300
400
500
600
700
800
900
1000
Ene
rgy
(eV
)
4s24p64d10nl
4d104f
4d105s
4d105p
4d105d
4d105f
4d105g4d106s4d106p
4d106d4d106f
4d106g4d106h
4s24p64d94fnl
4d94f2
4d94f5s4d94f5p
4d94f5d
4d94f5f
4d94f5g
IP=881.4 eV
Ag−like W
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• Beam energy required to generate excited states of Pd-like ions is reduced
0 Ag−like W
0
100
200
300
400
500
Ene
rgy
(eV
)
4s24p64d10nl
4d104f4d105s
4d105p
4d105d
4d105f
4d105g
4d106s4d106p
4d106d4d106f
4d106g4d106h
4s24p64d94fnl
4d94f24d94f5s
4d94f5p
4d94f5d
4d94f5f
4d94f5g
IP=358 eV
Ag−like Gd
Summary
EUV spectra of Gd, Dy and W ions from the NIST EBIT
• 59 new lines identified in Rb-like to Cu-like gadolinium
• ‘Potential lowering’ observed in 4fn ions
• Uses:
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• validate atomic / plasma codes predict trends in atomic structure
• model EUV sources for next-generation lithography
• diagnostics of hot plasmas in fusion devices such as ITER
Thanks
The Atomic Spectroscopy Group at NIST
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Acknowledgement : This work was supported by Science Foundation Ireland under grant number 07/IN.1/I1771 and in part by the Office of Fusion Energy Sciences of the U.S. Department of Energy.
The 17th ADAS WORKSHOP23 – 25 September 2012Château de Cadarache