Threshold energy for sputtering of monoatomic surfaces with noble gas ions

Sputtering has revolutionized nano- and micro-scale manufacturing, but can cause wear in crucial components in contact with plasmas. To control sputtering, a critical but elusive quantity is the threshold energy for sputtering initiation, often obtained from empirical extrapolation of sputtering yield data that have large uncertainties at low ion energies. Using molecular dynamics simulations, we quantify the sputtering threshold energies of monoatomic surfaces under the bombardment of noble gas ions at normal incidence angle across a broad range of ion-target combinations. We relate the resulting threshold energies to the ion-target properties through an evolutionary algorithm for symbolic regression, and show a strong functional dependence on the nucleus charge governing ion-target repulsion and the target density, in addition to the heat of sublimation and ion-target mass ratio in prior semi-empirical models. This new data-driven formulation improved predictions by an order-of-magnitude, and is applicable to crystalline and amorphous targets.