LIGHT-EMISSION FROM A SI TARGET DURING ION-BEAM SPUTTERING

The intensities of optical spectral lines from excited sputtered atoms under Kr+ ion bombardment of a Si target have been measured as a function of oxygen and nitrogen partial pressure. Si I lines are found to be quite sensitive to the presence of O-2 as expected, but not to N-2 up to the pressure of about 10(-5) mbar. Above 10(-5) mbar light intensities tend to fall with increasing oxygen pressure, but to rise with increasing nitrogen pressure. The beam-off transients of Si I lines at different oxygen coverages are also studied. From the pressure and time dependence of Si I spectral lines, the sputtering yield of adsorbed oxygen atoms on the Si surface is determined; the value is found to be close to unity for 300 keV Kr+ ion bombardment.