Plasma-Deposited Beryllium Carbide Coatings for Application to Inertial Confinement Fusion

Composite coatings containing beryllium are prepared by plasma-enhanced chemical vapor deposition at a substrate temperature as low as 250°C in a radio-frequency-induced cylindrical plasma reactor. Diethylberyllium is used as the precursor together with hydrogen as a coreactant gas. These coatings are characterized by Auger electron spectroscopy (AES), X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, electrical resistivity, and thermogravimetric analysis. AES indicates that the composition of the coatings reaches a steady level at a depth of 300 Å from the surface and maintains a constant composition throughout the thickness of the coatings. The characterization studies establish the dominant phase to be Be₂C. The coatings are also resistant to oxidation and hydrolysis in dry/moist air unlike bulk Be₂C. It is found that the coatings deposited close to the diethylberyllium inlet contain amorphous beryllium that is homogeneously dispersed in a Be₂C matrix. Films of ~5-m thickness with an acceptable permeability to H₂ are prepared. These coatings meet some of the major requirements of the ablator material for inertial confinement fusion target capsules.