Hafnia and silica film structures deposited by electron-beam evaporation

Background

Striated composite materials (SCM) are of interest since the material properties of the composite are different than those of the constituent materials, and they are a potential technique to create modified material mixtures with high laser-induced–damage thresholds. This approach has been successfully demonstrated for ion-beam-sputtered films, although the apertures are somewhat limited and thin-film stresses are typically high. Meanwhile, evaporated coatings have been used extensively and successfully for large-aperture, high-fluence laser coatings, but there are significant challenges depositing composite coatings for evaporated films.

Technology Overview

Researchers at the University of Rochester developed an approach to enable the deposition of SCM layers by using an electron-beam evaporation process in existing systems. This is done by simultaneous evaporation from two different electron-beam sources, but shielding the substrate such that deposition from only one source at a time is received. By rotating the substrate through the deposition zone above each source, the deposition of the two materials can be quickly alternated. This is very different than co-deposition of material mixtures, since individual control of the spatial uniformity of each material is maintained, enabling a uniform distribution of the material properties as well. By controlling the deposition zone size, evaporation rate, and substrate-rotation speed, the relative material content and SCM thickness can each be controlled.

Benefits

These films fabricated using hafnium dioxide and silicon dioxide—tested at 1053 nm with 600-fs pulses—exhibited intermediate refractive indices, with improved laser-induced damage thresholds and a more-compressive film stress relative to hafnia monolayers, suggesting that the use of such layers may significantly improve both the stress-induced deformation and LIDT of large-aperture, high-fluence components. Additionally, the ability to tailor the refractive index of the film would enable deposition of unique coating designs that are typically not easy with standard coating materials, and the increased film density—together with a shift to a more-compressive stress—could make this a viable approach to deposit coatings for low-humidity environments without risk of tensile stress failure.

Applications

Monolayer coatings

URV Reference Number: 3-20077
Patent Information:
Category(s):
Nanotechnology
For Information, Contact:
John Fahnervihtelic
Senior Licensing Manager
University of Rochester
585.276.6600
john.fahner-vihtelic@rochester.edu
Inventors:
James Oliver
Keywords: