Preparation and Characterization of Bilayer

Reflectance Standards for the EUV

David D. Allred1, Zach Strother2, and Nicole Brimhall1;

1BrighamYoung University, 2 Georgia Institute of Technology

BYU researchers have addressed the following concerns for those who would do VUV/EUV (Vacuum/Extreme Ultraviolet) optics in a conventional laboratory as opposed to a synchrotron facility:

1.Standards (now)

2.Mirror cleaning and storage. E. Strein discussed

3.Modeling

4.Sources/ spectrometers

I discuss the first in detail while not neglecting the final.

Outline1. Image- Goal 30.4 nm high & 58.4nm low2. Since Image 3. What is a standard?

1. Why?2. Robust, stble, cleanable, cheap and readily

fabricated and characterized etc.

4. Examples1. SiO2 on Si wafer2. Si on Ru

5. High Harmonic source.

IMAGE Mission http://image.gsfc.nasa.gov/

Launched Mar 25, 2000• Had 4 instruments • The Extreme Ultraviolet Imager was

designed to study the distribution of cold plasma in Earth's plasmasphere by imaging the distribution of He+ ions through their emission at 30.4 nm. (resonant scattering of light from solar corona. B. R. Sandel, A. L. Broadfoot, J. Chen, C. C. Curtis, R. A. King, T. C. Stone, R. H. Hill, J. Chen, O. H. W. Sigmund, R. Raffanti, David D. Allred, R. Steven Turley,  D. L. Gallagher, “The Extreme Ultraviolet Imager Investigation for the IMAGE Mission,” Space Science Reviews 91, 197-242 (2000).

EUV Pictures

EUV of May 24, 2000 bright aurora and plasmasphere tail

High Reflectivity Multilayer Mirror for He-II Radiation at 30.4nm in

Solar Physics Application• Jingtao Zhu, Zhanshan Wang, Shumin Zhang,

Hongchang Wang, Wenjuan Wu, Bei Wang, Yao Xu, Zhong Zhang, Fengli Wang, Lingyan Chen Institute of Precision Optical Engineering (IPOE), Tongji University, Shanghai 200092, China &

• Hongjun Zhou, Tonglin Huo• Attempt the a-periodic solution to reduce R at

58.4 nm but the minimum was at ~62 nm

What is a standard?

1. Why have one?

2. What should it be like?

1. Robust, stable, cleanable, cheap and readily fabricated and characterized etc.

2. Simple

Standards: Determining the optical properties of materials in the range (8 to 80 nm) would be benefited from stable, reliably, easy-to-prepare and characterize mirrors being available to researchers. Simple, single-surface mirrors with high

reflectance over broad spectral ranges, analogous to the role that materials like Al and Ag fill in the IR and visible, do not exist.

Multilayers are often used in lower wavelengths ranges to calibrate optical systems but these are expensive, are not broadband and often unstable.

• In place of these we are developing bilayers which exhibit strong interference fringes as a function of reflectance angle for large portions of the spectra. They show large interference fringes near the Brewster’s angle and acceptably large reflectance at near-normal incidence.

Recent attempts. Preparation and characterization of the standards.

1. Thermally oxidized Si

2. Ru/Si on Si

One class of standards is thermally oxidized silicon wafers, that is 20-40 nm thick SiO2 on Si.

These shows large fringes in the ~8 to 30 nm range. These wavelengths are of particular interest to us.

Looking at dirty samples.

• Genetic algorithm to come up with material combinations

• Another class is sputtered Ru-Si bilayers which can exhibit strong interference fringes at 30.4 and acceptable performance at 58.4 nm.

Bilayer: Silicon (400A) / Ruthenium (200A)

Si (400A)Ru (200A)------------------ SubstrateSiO2(20 A)Si (1 mm)

Reflectance at 304

Clearly no interference fringes at 584, but still good results at 304.

Schematic-

Extreme Ultraviolet Polarimeter Utilizing Laser-Generated High-

Order Harmonics• Nicole Brimhall, Matthew Turner, Nicholas

Herrick, David D.

• Allred, R. Steven Turley, Michael Ware, and Justin Peatross

• Submitted to Rev. Sci. Instr.

Summary

1. VUV is tough.

2. What is a standard?1. Robust etc.

3. Examples1. SiO2 on Si wafer

2. Si on Ru

4. High Harmonic source.