Light Ion-Beam Irradiation Damages in the Amorphous Films of Si<sub>3</sub>N<sub>4</sub>-SiC System Prepared by Plasma CVD

Abstract

For the application to first wall materials of fusion reactor, irradiation damages of Si3N4-SiC amorphous films that were prepared by plasma CVD method have been investigated experimentally by use of an intense pulsed light-ion beam. The ionbeam irradiation was carried out by using a magnetically insulated diode of flat-type, where an external transverse magnetic field was applied to insulate the motion of electrons. The inductively calibrated diode voltage was being kept constant at 650kV, and the dose rate of the beam was 1013 ions cm-2 shot-1 (H+ ion). The content of the H+ ion found to be more than 80%, and the remainder consisted of C+, C2+, C3+ and H2+ ions. From the changes of surface texture, film thickness, composition, and cross-sectional views, we evaluated these irradiation damages. Blistering for SiN1⋅42(-Si3N4) film, flaking for SiC1⋅04(-SiC) film and the intermediate texture between blistering and flaking for SiN0⋅65C0⋅62 film were observed after the irradiation, A ccording to the observation of cross section of the films, the irradiation damage was limited in the surface layer, and peeling off of the whole film from the substrate (316 stainless steel) did not occur. Erosion rate (the decrease in film thickness per one shot of irradiation) was in the range from 0.46 to 0.73μm shot-1, where the SiN1⋅42 film showed the smallest rate. N and C contents in the films were found to have decreased, and Si content was found to have increased by EPMA measurements.