Effect of chemical bonding on positive secondary-ion yields in sputtering

We have studied the effect of chemical bonding on the emission of positive secondary ions from solid surfaces in static mode sputtering. In all the three systems investigated, N-Si(100), O-Si(100), and O-Ge(111), the Si+ and Ge+ yields were enhanced by at least 2 orders of magnitude. X-ray photoemission showed that the ion yields were linearly related to the amount of surface nitrides or oxides formed during the reactions. The ion yields were site specific and showed emission-velocity and angle dependences. The results are compared to the predictions of a recently proposed bond-breaking model. © 1987 The American Physical Society.