Download ppt

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.
Outline
1. Image- Goal 30.4 nm high & 58.4nm low
2. Since Image
3. What is a standard?
1. Why?
2. Robust, stble, cleanable, cheap and readily
fabricated and characterized etc.
4. Examples
1. SiO2 on Si wafer
2. 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)
------------------ Substrate
SiO2 (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 HighOrder 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. Examples
1. SiO2 on Si wafer
2. Si on Ru
4. High Harmonic source.