Energy dependence of bombardment effect of 10-540-keV C ions on a Si surface

Narumi, Kazumasa; Naramoto, Hiroshi*; Yamada, Keisuke; Chiba, Atsuya; Saito, Yuichi; Takahashi, Yasuyuki*; Maeda, Yoshihito

We have measured Si sputtering yield as a function of energy and the number density of Si atoms displaced from the lattice site as a function of ion fluence for 10-540-keV C ions. Si sputtering yields were determined by measuring thickness change of an amorphous layer, which had been prepared by 200-keV Ar irradiation, with Rutherford-backscattering spectrometry. The sputtering yield has the maximum, ca. 600 per C ion, around 100-keV. Comparing with the monatomic-ion-induced sputtering yield predicted by the linear-cascade theory by Sigmund, nonlinear effect on sputtering yield has been found: It depends on the ion energy and is very large around the energy where the sputtering yield has the maximum. The areal density of Si atoms displaced from the lattice site was determined from the area of a surface peak of backscattering yields of 2-MeV He ions. Fluence dependence of the areal density of the disordered Si atoms shows monotonic increase at lower fluence; then, it reaches a constant depending on the energy at higher fluence. Assuming a cylindrical volume, the volume affected by single-C-ion bombardment has been determined from the fluence dependence. Energy dependence of the thickness and the cross section of the damaged volume will be discussed.