Specifics of Damageability of the Silicon Single Crystal under Exposure of Powerful Plasma Streams and Fast Helium Ions

摘要

The results of experiments on the impact of fast helium ions (E_i ～ 100 keV) and helium plasma (v ～ 2 × 10~7 cm/s) on a silicon single crystal plate in the Vikhr plasma focus (PF) installation with radiation power density in the range of q ≈ 10~6-10~7 W/cm~2 are presented. It is shown that, at low values of q = 10~6-10~(11) W/cm~2, the damageability of silicon is due to its surface sputtering mainly in the zone of mechanical defects, while with more intense irradiation (10~8＜ q ≤ 10~(11) W/cm~2) the processes of melting and evaporation of the surface layer occur with the formation of structural defects in the form of waves, flows, bubbles, craters and microc-racks. The specific nature of damage of the Si plate at high power density and a large number of pulsed beam-plasma impacts (q ≥ 10~9 W/cm~2, N = 50) is described. It is associated with the formation of a brittle fine-crystalline surface layer, which is easily separated from the base material and disintegrates in the form of a powder of particles of micron and nanoscale size. This result is a consequence of the action of thermal stresses in combination with the implantation of helium ions into the material as well as the possible influence of shock waves generated in the Si target during hard irradiation regimes. The presence of copper, carbon, and nitrogen on the silicon surface after its beam-plasma treatment, as well as an increase in the electrical resistivity on the irradiated side and backside of the plate, is noted. The results obtained are discussed taking into account the features of the experiments in the PF setup.