Lutetium aluminum garnet

Lutetium - aluminum - garnet ( LuAG for short, English lutetiumaluminium garnet ) is an artificially produced crystalline compound with the chemical composition Lu ₃ Al ₅ O ₁₂ . Yttrium-aluminum-garnet (YAG) and yttrium-iron-garnet (YIG)are similar in structure and also artificial.

properties

LuAG is a colorless material with a high refractive index (2.1 at 193 nm wavelength ). Furthermore, it shows a comparatively high transparency in the ultraviolet (UV) spectral range. The absorption coefficient at 193 nm is 1.1 to 1.4 cm ⁻¹ .

LuAG has the same crystal structure as the more well-known YAG, that is, it crystallizes with the highest degree of symmetry in the cubic crystal system (crystal class cubic- hexakisoctahedral ). However, the density of LuAG at 6.71 g / cm³ is higher than that of YAG (4.55 to 4.65 g / cm³), which is caused, among other things, by the replacement of the yttrium ions by the heavy lutetium ions. As a result, it shows better scintillation properties.

LuAG doped with cerium shows scintillation with luminescence in the visible spectral range. This makes it a candidate as a detector material for detecting high energy photons .

use

Due to its high transparency in the UV range, LuAG is suitable as a material for UV lenses, for example for high-quality lens systems in photolithographic exposure systems such as steppers and scanners . Due to the proximity of the band gap (6.9 eV corresponds to 176.7 nm) to the currently used wavelength of 193 nm ( ArF - excimer laser ) in photolithography, LuAG must be available in a highly pure form, because even minor impurities would be absorbed in it Let the spectral range increase noticeably and the material would no longer be suitable for this application.

Individual evidence

1. ↑ ^{a b c} Yayi Wei, Robert L. Brainard: Advanced processes for 193-nm immersion lithography . SPIE Press, 2009, ISBN 978-0-8194-7557-2 .
2. ↑ ^{a b} Chris A. Mack Gabriel Y. Sirat, Michael Goldstein: Uniaxial Crystal Last Optical Element for Second- and Third-Generation Immersion Lithography ( Memento of November 3, 2013 in the Internet Archive ). 4th International Symposium on Immersion Lithography, 8. – 11. October 2007 Keystone, Colorado ( Memento of November 3, 2013 in the Internet Archive ) (poster; with further material properties).
3. ↑ John H. Burnett: High-index materials for 193 nm immersion lithography . In: Proceedings of SPIE . San Jose, CA 2004, pp. 611-621 , doi : 10.1117 / 12.600109 .
4. ↑ Kamran Said Karim: Manufacture of polycrystalline scintillators for positron emission tomography (PET) . Forschungszentrum Jülich, 2010, ISBN 978-3-89336-610-1 , p. 27 .
5. ↑ Nerine J. Cherepy, Joshua D. Kuntz, Thomas M. Tillotson, Derrick T. Speaks, Stephen A. Payne, BHT Chai, Yetta Porter-Chapman, Stephen E. Derenzo: Cerium-doped single crystal and transparent ceramic lutetium aluminum garnet scintillators . In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment . tape 579 , no. 1 , July 21, 2007, p. 38-41 , doi : 10.1016 / j.nima.2007.04.009 .
6. ↑ Lutz Parthier, Gunther Wehrhan, Frank Seifert, Marcus Ansorg, Tilo Aichele, Christoph Seitz: High-Index Lens Material LuAG: Development Status and Progress ( Memento of the original from November 3, 2013 in the Internet Archive ) Info: The  archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . 2008 SEMATECH Litho Forum, 12.-14. May 2008, Bolton Landing (Lake George), NY ( Memento of the original from February 28, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (Lecture; including images of a LuAG single crystal and the crystal structure).