Fluoride thin film formation with low optical absorption by gas cluster ion beam assisted deposition
✍ Scribed by S. Nakazawa; N. Toyoda; K. Mochiji; T. Mitamura; I. Yamada
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 491 KB
- Volume
- 261
- Category
- Article
- ISSN
- 0168-583X
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✦ Synopsis
Gas cluster ion beam (GCIB) shows characteristics of low-energy irradiation effect and dense energy deposition. GCIB-assisted deposition is expected to be used for high-quality fluoride film formation, although these films are sensitive to damage by ion irradiation. In this study, LaF 3 and MgF 2 films were deposited by SF 6 -GCIB-assisted deposition. When the acceleration voltage was 3-7 kV, the deposited LaF 3 film had a high packing density, small columnar structure, and very flat surface. The average roughness of the LaF 3 film surface was 0.25 nm by the surface smoothing effect of the GCIB. The LaF 3 film density showed 5.90 g/cm 3 , which was very close to the theoretical density of crystalline LaF 3 . The refractive index (n) of the LaF 3 film increased from 1.62 to 1.72 with an increase in the ion current density. The extinction coefficient (k) was 1 • 10 À3 at a wavelength of 193 nm. By the deposition of a thin layer of Al 2 O 3 (extinction coefficient: 5 • 10 À3 ) on the quartz substrate as an interfacial film, a strong adhesive fluoride film was obtained.