Surface structure of silicon carbide irradiated with helium ions with monoenergy and continuous energy distributions

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Abstract
Silicon carbide was irradiated at room temperature and 600 °C with helium ions with monoenergy (3–100 keV) and continuous energy distribution ranging from 0.5 keV to 20 keV up to a total dose of 1×1019 ions/cm2 using an ion accelerator controlled by a microcomputer. For room temperature irradiation, porous structures appear on the surface of samples irradiated to dose of ∼5×1018 ions/cm2, and the damaged layer is easily removed from underlying undamaged layer by ultrasonic vibrations. On the other hand, for target temperature of 600 °C, such porous surface structures are not observed, which is due to thermal annealing. It has been shown that the surface deformation depends strongly not only on the implantation profile, but also on irradiation modes of helium ions. Flaking is completely avoided by prebombardment of helium ions with continuous energy distribution, which deliberately produces a pathway for gas release. In order to simulate wall erosion due to helium bombardment, silicon carbide was also irradiated with a Maxwellian distribution. No blistering or flaking is observed for an average energy of 3 keV.