The effects of oxygen and nitrogen adsorption on secondary ion energy spectra

Abstract

The detailed variation of the energy spectra of ions sputtered from pure materials as the partial pressure of reactive gas changes was studied. The results show that the contribution of secondary ions from reacted versus clean surfaces varies smoothly as the gas pressure (and thus coverage) is increased for most surfaces. Sudden changes in the energy spectra are observed for Ni, Co, and W in the presence of oxygen, apparently corresponding to incorporation of oxygen into the surface lattice. The energy spectra are therefore very sensitive to changes in the surface, and should be very useful in oxidation or adsorption studies. The analytical consequences of changes in the energy spectra are discussed. As the spectra change, the transmission coefficients (bandpass efficiencies) for the ions alter, thereby affecting the apparent signal intensities. The optimum analytical condition is deduced from the data.