1 The Effects of Oxidation on the Index of Refraction of Uranium Thin Films in the Extreme Ultraviolet Heidi Dumais

2 “EUV” In General 5 – 30 nm Applications: – Photolithography – Microscopy – Astronomy Issues: – Absorption – Vacuum – Multilayers

3 Magic of Multilayers

4 Measurements at ALS

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? 5

6 Samples for R and T Measurements Compute reflectance and/or transmission by iterating through thin film layers = Parratt Si Diode Si Deadlayer SiO 2 UO x Sample Contamination x0x0 x 

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 7

Thicknesses 8

Imaginary Index 9

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Compared to in situ U measurements 11

Real Index 12

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Conclusions Imaginary Part: – Naturally oxidized looks like higher oxide, U 3 O 8 – Higher oxide peaks shift toward higher energy Real Part: – Needs some finagling Need to relate electronic structure from indices 14

15 Acknowledgements 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