Heat treatment of glassy carbon implanted with cesium at room and high temperatures

Abstract

The effect of annealing temperature on the surface morphology and on the diffusion of cesium ions implanted into glassy carbon (Sigradur® G) is reported. The samples were implanted with 360 keV cesium ions to a fluence of 2 × 1016 ions/cm2 at room temperature, at 350 and at 600 °C. The room temperature implanted samples were isochronally vacuum annealed for 1 h at temperatures from 200 to 600 °C. All samples were studied by Rutherford backscattering scattering (RBS) and scanning electron microscopy (SEM).

During implantation a strong redistribution of the cesium ions towards the surface is observed, which occurs already at room temperature and enhances at elevated temperatures. However, almost no cesium ions are lost in that process. Contrary, annealing at elevated temperatures results not only in a diffusion and redistribution of cesium, but also in a significant sublimation/evaporation of cesium into the vacuum. This suggests that during implantation some meta-stable compound is formed which prevents a cesium loss. SEM pictures of the samples show that implantation and subsequent annealing strongly influence the surface structure of the glassy carbon.