Application of an extended linear cascade model to the sputtering of Ag, Au, and Pt by heavy atomic and molecular ions

Sputtering yields of Ag, Au, and Pt have been measured for monatomic and polyatomic ions of P, As, Sb, and Bi over the energy range 10–250 keV. It is shown that the energy dependence of the sputter yield follows the energy dependence of the surface deposited energy FD(0) when the calculated FD(0) values are obtained from a Monte-Carlo simulation. Using the Monte-Carlo values, the observed sputtering yield is found to obey the linear model of Sigmund at low FD (0), but deviates significantly at high FD (0). It is proposed that the high sputtering yields observed (up to ∼800) and the region of nonlinear dependence on FD (0) can in part be accounted for by assuming that a critical sputtering yield exists, above which surface topographical features, such as craters, can be formed. Assuming all the sputtered atoms originate from a hemispherical crater geometry of radius hs, it is found that much better agreement between measured and calculated values occur if the total energy considered in calculating the sputtering yield is taken as ℱhs0FD(x)dx. It is also demonstrated that the associated topography developed, plus a possible contribution from an effectively reduced surface binding energy, which may occur as the result of a collision spike and multimer emission, could play a significant role such that the measured sputtering yield would be higher than the revised calculated values which are still appropriate to a planar surface and a full binding energy.