We attempt to give a logically coherent definition of the term "sputtering threshold," and establish criteria which may determine an experimental threshold. The Silsbee chain mechanism and the experimentally observed preferred direction of emission from single crystals are used to establish a threshold theory. Two models are required, one generally applicable when the mass ratio is less than one, and another when it is greater than one. Single-crystal threshold laws are obtained, and polycrystalline laws follow for face-centered cubic crystals by averaging the single-crystal forms. An approximate technique for the evaluation of surface atomic binding energies is presented so that the thresholds can be compared with experimental results. In all cases the theoretical thresholds are less than or comparable to experimental "thresholds."

• Received 27 January 1961

DOI:https://doi.org/10.1103/PhysRev.122.1421