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 radiofrequency-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 Angstrom 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 approximately5-microm 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