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Open AccessArticle

Improving Thickness Uniformity of Mo/Si Multilayers on Curved Spherical Substrates by a Masking Technique

1
MOE Key Laboratory of Advanced Micro-Structured Materials, No.1239 Siping Road, Shanghai 200092, China
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Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
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Sino-German College of Applied Sciences, Tongji University, Shanghai 200092, China
*
Author to whom correspondence should be addressed.
Coatings 2019, 9(12), 851; https://doi.org/10.3390/coatings9120851
Received: 17 November 2019 / Revised: 8 December 2019 / Accepted: 10 December 2019 / Published: 12 December 2019
In this work, a masking technique was used to improve the thickness uniformity of a Mo/Si multilayer deposited on a curved spherical mirror by direct current (DC) magnetron sputtering with planetary rotation stages. The clear aperture of the mirror was 125 mm with a radius of curvature equal to 143.82 mm. Two different shadow masks were prepared; one was flat and the other was oblique. When using the flat mask, the non-uniformity considerably increased owing to the relatively large gap between the mask and substrate. The deviation between the designed and measured layer thickness and non-uniformity gradually reduced with a smaller gap. The second mask was designed with an oblique profile. Using the oblique mask, the deviation from multilayer thickness uniformity was substantially reduced to a magnitude below 0.8% on the curved spherical substrate over the clear aperture of 125 mm. Multilayers still achieved a smooth growth when deposited with obliquely incident particles. The facile masking technique proposed in this study can be used for depositing uniform coatings on curved spherical substrates with large numerical apertures for high-resolution microscopes, telescopes, and other related optical systems. View Full-Text
Keywords: layer uniformity; magnetron sputtering; shadow mask; multilayer; curved substrate layer uniformity; magnetron sputtering; shadow mask; multilayer; curved substrate
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MDPI and ACS Style

Zhang, Z.; Qi, R.; Yao, Y.; Shi, Y.; Li, W.; Huang, Q.; Yi, S.; Zhang, Z.; Wang, Z.; Xie, C. Improving Thickness Uniformity of Mo/Si Multilayers on Curved Spherical Substrates by a Masking Technique. Coatings 2019, 9, 851.

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