An approach to calculate sputtering rates in glow discharges by using a new crater volume evaluation method

摘要

The determination of sputtering rates is, commonly, an important parameter in glow discharge analyses. In particular, in those quantification procedures where the emission yield plays an important role in calibrations, the correct calculation of such value becomes crucial. The volumetric methods to calculate the sputtering rates (they offer a higher accuracy than the gravimetric ones) aim to measure the crater volume created in the sample during the analysis. The standard approximation assumes the crater as a cylinder and so it is mandatory to achieve crater shapes with a flat bottom and walls perpendicular to it. But in practice, craters show many times a convex (or concave) bottom which depends on the measurement conditions. In this work is presented a new approach to determine the crater volume based on a numerical model which calculates the crater volume from a 2D profile. Eight craters were made in a stainless steel at different experimental conditions (to obtain varied crater shapes) and the values offered by the model (a computer software) were compared with those obtained using an optical profilometer. The discrepancy between methods is lower than 15%. Moreover, 68 crater volumes were calculated by using a mathematical approximation to the crater profile (fitting it by analytical functions and integrating) and were compared with those reported by the numerical model, giving rise to discrepancies below than 5% in most cases. (C) 2007 Elsevier B.V. All rights reserved.