Influence of CH4–Ar ratios on the composition, microstructure and optical properties of Be2C films synthesized by DC reactive magnetron sputtering

Abstract

Beryllium carbide (Be₂C) films were first deposited on optical quartz substrates by DC reactive magnetron sputtering on a beryllium target with variable CH₄–Ar ratios. The influence of CH₄–Ar ratios on the composition, microstructure and optical properties were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscope, atomic force microscopy, scanning electron microscope and UV-vis spectrum. The main component in the films prepared at lower CH₄–Ar ratios (<5%) was Be₂C, while hydrocarbon (CH) films were formed at higher CH₄–Ar ratios (>15%). The films exhibited a nanocomposite structure consisting of Be₂C nanocrystals (3 to 5 nm in size) embedded in amorphous hydrocarbon matrices. A smooth surface and columnar structure on the cross-sectional view were revealed. Besides, the depositing rates reached ∼125 nm h⁻¹, which were significantly higher than that of RF reactive magnetron sputtering. High transparency (>50%) of the Be₂C films in the visible region as well as an even higher transparency (>80%) in the near-infrared region were demonstrated. Finally, the dispersion of the optical constants of Be₂C films is presented, and the optical bandgaps were evaluated to be ∼2 eV. The good properties of Be₂C films prepared by DC reactive magnetron sputtering showed that this material could be a potential candidate for application to inertial confinement fusion targets.