Sputter yields of surfaces with nanoscale textures: Analytical results and Monte Carlo simulations

We find the spatially averaged sputter yield Y analytically for non-planar surfaces that have slowly varying surface heights h 1/4 h(x, y). To begin, nonlocal effects like redeposition of sputtered material and secondary sputtering are neglected. We show that the leading order corrections to Y are proportional to the spatial averages of (partial derivative h/partial derivative x)(2) and (partial derivative h/partial derivative y)(2). The constants of proportionality can be written in terms of the first and second derivatives of the sputter yield of a flat surface with respect to the ion incidence angle 0. For a range of 0 values, Y is a decreasing function of the amplitude of the surface texture. We also determine how the contribution of redeposition to Y depends on the amplitude and characteristic lateral length scale of the surface morphology. As a test of our theory and to quantify the roles of redeposition and secondary sputtering, we performed Monte Carlo simulations of sputtering from Si targets with sinusoidal surfaces by 1 keV Ar thorn ions. The theory agrees remarkably well with our Monte Carlo simulations. Our simulations also lead to the notable result that atoms that are sputtered and then strike the surface can themselves cause significant sputtering. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/5.0137324

Automated summary

In this study, we analytically determine the average sputter yield Y for non-planar surfaces with slowly varying heights. We neglect nonlocal effects such as redeposition of sputtered material and secondary sputtering. Our analysis reveals that the leading order corrections to Y depend on the spatial averages of the square of the height gradients in the x and y directions. The constants of proportionality can be expressed in terms of the derivatives of the sputter yield for a flat surface with respect to the ion incidence angle.