Potential sputtering of hydrogen atoms on various surfaces with slow highly-charged ions

Several recent findings on a new sputtering mechanism of hydrogen with slow highly-charged ions are discussed. The sputtering yields of protons were proportional to q∼5 for q≲10 independent of the surface condition for both untreated and well-defined surfaces, where q is the charge state of the ion. This q∼5 dependence started to level off for q≲10. The yield for the Si(100)1×1–H surface was ten times larger than that for the Si(100)2×1–H surface although the stoichiometric hydrogen abundance of the former is only twice that of the latter. The key quantity to govern the yield is proposed to be surface roughness, which also influences the energy distribution of sputtered protons. These findings were consistently explained with a pair-wise potential sputtering model involving two successive electron transfers which follow the classical over barrier mechanism.