LOW-ENERGY ION IRRADIATION OF H-TERMINATED SI(001) - HYDROGEN SPUTTERING, BEAM-INDUCED (2X1) RECONSTRUCTION, AND SI EPITAXY

Low energy (15-50 eV) noble gas ion irradiation at low temperatures ( < 300 degrees C) enables formation of a Si(001)-2 X 1 surface reconstruction that has been hydrogen-terminated by a hydrofluoric acid dip prior to irradiation. Using 15 eV He+ irradiation, a (2 X 1) reconstruction can be formed at temperatures as low as 50 degrees C, the lowest temperature ever reported for formation of this reconstruction. The (2 X 1) reconstruction occurs as a result of surface hydrogen removal by sputtering and recoil implantation into the silicon substrate. Molecular dynamics simulations of low energy irradiation of a hydrogen-terminated silicon surface indicate that chemically-enhanced physical sputtering of silicon occurs in addition to physical sputtering of hydrogen. The hydrogen sputtering yield is found to be strongly dependent on surface hydrogen coverage. The results suggest that low energy ion irradiation can be used to tailor the hydrogen coverage, and thus also the chemical reactivity of the silicon surface.