Detection of anisotropy in the optical constants of quartz crystals for soft X-rays

In the PTB, methods for determining the optical constants of materials with synchrotron radiation have been established

Comparison of the measured reflections for the crystal directions (100) and (001) at a fixed angle of incidence θi around the Si L2,3 absorption edges. The lower map shows the respective anisotropy. © PTB

Quartz is an important substrate material for semiconductor structures and is used in a wide variety of industrial fields, for example as a substrate for various mirrors, nanostructures or other functional surfaces features. For the development of new optical components and the corresponding modeling of the light-matter interaction, the accurate knowledge of optical material parameters is of exceeding importance.

In recent years, methods for determining the optical constants of materials with synchrotron radiation have been established in the PTB. A cooperation of the PTB (working groups 7.14 EUV Nanometrology, 7.12 EUV Radiometry and 7.24 X-ray Spectrometry) with the National Institute for Standards and Technology (NIST) in the U.S. has now resulted in improved data sets for the optical constants of quartz in the spectral range of soft X-rays. The values reconstructed from reflectance measurements not only extend the existing literature with detailed data at the silicon and oxygen absorption edges, but also substantiate the postulated anisotropy of the quartz crystal. The results were confirmed by simulations using the ab-initio Bethe-Salpeter equation developed at NIST. These simulations are critical to better predict the fine structure at the edges and opens new possibilities for chemical analysis. This new dataset is part of the ATMOC initiative for the development of a European optical constants database which is being driven by PTB.

Publication:

The anisotropy in the optical constants of quartz crystals for soft X-rays
A. Andrle, P. Hönicke, J. Vinson, R. Quintanilha, Q. Saadeh, S. Heidenreich, F. Scholze, V. Soltwisch
J. Appl. Cryst. 54, 1-7 (2020)
 

Contact:

Physikalisch-Technische Bundesanstalt
Dep. 7 Temperature and Synchrotron Radiation

Anna Andrle
7.14 EUV-Nanometrology
Email: Anna.Andrle(at)ptb.de

Press release PTB, 18 March 2021