Optical, composition, durability, and environmental properties of the microwave plasma-assisted sputter-deposited silicon nitride

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Lindsay, Connor and Garcia Nuñez, Carlos and Fleming, Lewis and Brinkley, Ian and Pomfret, Jonathan and Mazur, Michal and Kot, Malgorzata and Zhu, Wenzhong and Saunders, Kirstin and Reid, Stuart and Herguedas, Elen and Redondo-Cubero, Andres and Gibson, Des (2026) Optical, composition, durability, and environmental properties of the microwave plasma-assisted sputter-deposited silicon nitride. Applied Optics, 65 (5). A176-A186. ISSN 1559-128X (https://doi.org/10.1364/ao.578043)

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Abstract

A study is presented of the optical, mechanical, composition, durability, environmental, and structural properties of silicon nitride thin films deposited at room temperature using a vertical axis rotating drum-based microwave plasma-assisted sputter system. The deposited material composition was investigated using both X-ray photoelectron spectroscopy (XPS) and elastic recoil detection analysis with time of flight (ERDA-TOF). The results indicate that the layers present a uniform composition with thickness and despite the incorporation of impurities, the Si/N ratio remains close to stoichiometric Si 3 N 4 . The deposited material provides homogeneous low dispersion—with a refractive index of approximately 1.98 over a wide transmittance range (350 nm to 5 µm). Additionally, the single layer silicon nitride was found to be durable with a hardness, Young’s modulus, and compressive stress of 31 GPa, 240 GPa, and −454MPa, respectively. The coating was subjected to and passed external surface environmental tests covered by MIL-C-48497A durability requirements (adhesion, abrasion, and temperature/humidity cycling) and MIL-C-675C (para 4.5.9) salt spray. Moreover, 10,000 wipes on the TS1888 (para 5.4.3) sand slurry abrasion test were achieved with no visible signs of damage. A silicon nitride/silica multilayer durable broadband visible anti-reflection coating is demonstrated, passing the same range of durability and environmental tests as single layer silicon nitride.

ORCID iDs

Lindsay, Connor, Garcia Nuñez, Carlos, Fleming, Lewis, Brinkley, Ian, Pomfret, Jonathan, Mazur, Michal, Kot, Malgorzata, Zhu, Wenzhong, Saunders, Kirstin, Reid, Stuart ORCID logoORCID: https://orcid.org/0000-0002-9728-3507, Herguedas, Elen, Redondo-Cubero, Andres and Gibson, Des;
CORE (COnnecting REpositories)