Potential sputtering of protons from hydrogen- and H2O-terminated Si(100) surfaces with slow highly charged ions

A potential sputtering mechanism of hydrogen has been studied for impacts of slow highly charged Xeq+ ions (<5 keV, q = 4-12) on well-defined H-terminated and water-saturated Si(I 0 0) surfaces. It was found that the sputtering yields of protons were proportional to q(gamma) (gamma similar to 5) for both the Si(1 0 0)2 x 1-H and Si(1 0 0) 1 x 1-H surfaces, although the absolute yield for the Si(1 00)1 x 1-H surface was 10 times larger than that for the Si(1 00)2 x 1-H surface, i.e. the sputtering efficiency per one H-Si bond for the Si(1 0 0) 1 x 1-H surface is five times larger that for the Si(1 0 0)2 x 1-H surface. The proton sputtering efficiency from a H-O-Si bond was extracted from measurements of the water-saturated surface, which was similar to8 times larger than the H-Si bond of the Si(1 0 0)2 x 1-H surface. An effective distance of the proton from its substrate was proposed to be the key parameter to govern the yield, which also influences the energy distributions of sputtered protons. These findings are consistently explained with a pair-wise bond-breaking model induced by a double electron capture, where the classical over barrier process plays an essential role. (C) 2003 Elsevier Science B.V. All rights reserved.