Effect of substrate temperature on the microstructure and properties of Be₂C films: Aim to advance its applications as ICF ablator

Beryllium carbide films were deposited on quartz substrates by DC reactive magnetron sputtering of beryllium in the mixture of CH₄-Ar plasma. The influence of substrate temperature on the composition, microstructure and optical properties were characterized by suitable analytical techniques. Experimental results revealed that the composition is independent of substrate temperature and all films are mainly composed of Be₂C. Untextured polycrystalline Be₂C coatings with smooth surface (Ra < 4 nm) were obtained at low substrate temperature (85–175 °C), while it evolved into porous columnar crystal structure with rougher surface as the temperature increasing. These films exhibited fine grains (<26 nm) and high densities. High speed deposition (>220 nm/h) of Be₂C films was realized in this work, representing the current highest deposition rate by reactive magnetron sputtering. The optical measurements showed an average transmittance ∼40% in visible region and ∼84% in near-infrared region for Be₂C films. The optical bandgap, evaluated by Tauc's method, was about 1.9 eV despite of substrate temperature. This work represents a significant step toward preparing high quality Be₂C films and benefits the application of Be₂C as ICF ablator. - Highlights: • Be₂C films are efficiently prepared by DC reactive magnetron sputtering. • The microstructure is subjected to the substrate temperature while composition is not. • High quality (R_a < 5 nm, ρ ∼ 2.13 g/cm³) Be₂C films are obtained at proper temperature. • The optical bandgap of polycrystal Be₂C films are firstly investigated and are ∼1.9 eV.