Transcript The Effects of Oxidation on the Index of Refraction of Uranium Ultraviolet

The Effects of Oxidation on the
Index of Refraction of Uranium
Thin Films in the Extreme
Ultraviolet
Heidi Dumais
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“EUV” In General
5 – 30 nm
Applications:
– Photolithography
– Microscopy
– Astronomy
ssues:
– Absorption
– Vacuum
– Multilayers
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Magic of Multilayers
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Measurements at ALS
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IAA in the EUV
• U in IMAGE mission mirror didn’t reflect as predicted
• CXRO predicts optical constants from IAA, best at high
energies
• Does it work for U in XUV?
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Samples for R and T Measurements
Contamination
x0
x
• Compute reflectance and/or
transmission by iterating through
thin film layers = Parratt
UOx Sample
q
SiO2
Si Deadlayer
Si Diode
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Procedure
1. Fit R runs to Parratt (vary index and thickness) →
thickness
2. Fit T runs to model (vary alpha) → beta
3. Fit T runs to Parratt (vary n) → n
4. Fit R runs to Parratt (vary thickness) → better
thickness
5. Lather, rinse, repeat
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Thicknesses
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Imaginary Index
9
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Compared to in situ U measurements
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Real Index
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Conclusions
• Imaginary Part:
– Naturally oxidized looks like higher oxide, U3O8
– Higher oxide peaks shift toward higher energy
• Real Part:
– Needs some finagling
• Need to relate electronic structure from indices
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Acknowledgements
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R.S. Turley and D.D. Allred
Rocky Mountain NASA Space Grant Consortium
Zephne Larsen, Keith Jackson, and Alison Wells
Eric Gullikson, ALS staff and DOE
Brigham Young University Physics & Astronomy
Department
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