Mechanisms of sputtering of Si in a Cl2 environment by ions with energies down to 75 eV

Sputtering of Si in a Cl2 environment by Ar+ and Xe+ ions with energies down to 75 eV has been investigated. Mass spectra and time-of-flight distributions of the sputtered species have been measured. Under 75-eV Ar+-ion bombardment of the Si target, SiCl, SiCl2, SiCl3, and/or SiCl4 are sputtered. When increasing the ion energy the SiCl4 contribution decreases in comparison with SiCl. This is caused by the fact that the newly formed Si-Cl compounds are sputtered at a high rate compared to the rate of SiCl4 formation. Time-of-flight distributions indicate that under 100-eV Ar+-ion bombardment the species are not sputtered by a collision-cascade mechanism. The spectra can be fitted by Maxwell--Boltzmann distributions at a high (>2000 K) temperature. Increasing the Ar+-ion energy to approximately 250 eV the time-of-flight spectra of the sputtered species change from Maxwell--Boltzmann-like into spectra as expected for a collision-cascade mechanism. For low-energy Xe+ ion bombardment the sputtered species also show Maxwell--Boltzmann time-of-flight distributions. The change from Maxwell--Boltzmann to collision-cascade distributions occurs at higher ion energies than for Ar+-ion bombardment. The results obtained for low ion energies are discussed in terms of evaporation from an ion-induced hot spot