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.