Determining the Optical Constants of EUV Reflectors Jedediah Johnson Dr. David Allred

Talk Outline Background physics/applications Background physics/applications Project Motivation Project Motivation Previous measurement techniques Previous measurement techniques Current sputtered diode research Current sputtered diode research

Reflectors in EUV range EUV range is about Å EUV range is about Å General Challenges: General Challenges: - hydrocarbon buildup - absorption - high vacuum needed Complex index of refraction: Complex index of refraction: ñ=n+ik

EUV Reflectors Light interacts principally with electrons. Light interacts principally with electrons. More electrons = higher the theoretical reflectance. More electrons = higher the theoretical reflectance. High density desired. High density desired.

Applications of EUV Radiation EUV Lithography Images from and Soft X-ray Microscopes Thin Film or Multilayer Mirrors EUV Astronomy The Earth’s magnetosphere in the EUV

Optical Constants Precise optical constant data allows scientists to engineer reflectors for specific projects. Precise optical constant data allows scientists to engineer reflectors for specific projects. R+T+A=1 R+T+A=1

Optical Constant Determination from Transmission Measurements CXRO has compiled optical constants which were usually measured from transmission measurements and Kramers-Kronig analysis

Kramers-Kronig Analysis Integral evaluated from zero to infinity (approximations introduced) Numerical methods or complex analysis required

Computer and Measured Reflectance vs. Wavelength Differences in the measured reflectance of thorium and the reflectance computed from CXRO constants call into question the accuracy of currently published data.

Simultaneous Reflection and Transmission Measurements

First data acquired with new diodes

Comparison with previous transmission window data

Conclusions We believe our methods will provide the most accurate optical constant measurements in the EUV. We believe our methods will provide the most accurate optical constant measurements in the EUV. Remainder of data taken in March 2005 must be analyzed and fit. Remainder of data taken in March 2005 must be analyzed and fit.

Acknowledgments BYU XUV Research Group colleagues BYU XUV Research Group colleagues Dr. David D. Allred Dr. David D. Allred Dr. R. Steven Turley Dr. R. Steven Turley BYU Physics Department Research Funding BYU Physics Department Research Funding