Point-defect properties of, and sputtering events in, the {001} surfaces of Ni₃Al. II. Sputtering events at and near surfaces

Abstract

Atomic recoil events at and near {001} surfaces of Ni₃Al due to elastic collisions between electrons and atoms have been simulated by molecular dynamics to obtain the sputtering threshold energy as a function of atomic species, recoil direction and atomic layer of the primary recoil atom. The minimum sputtering energy occurs for adatoms and is 3.5 and 4.5 eV for Al and Ni adatoms on the Ni–Al surface (denoted ‘M’), respectively, and 4.5 eV for both species on the pure Ni surface (denoted ‘N’). For atoms within the surface plane, the minimum sputtering energy is 6.0 eV for Al and Ni atoms in the M plane and for Ni atoms in the N surface. The sputtering threshold energy increases with increasing angle, θ, between the recoil direction and surface normal, and is almost independent of azimuthal angle, ϕ, if θ<60°; it varies strongly with ϕ when θ>60°, with a maximum at ϕ = 45° due to ⟨{110}⟩ close-packed atomic chains in the surface. The sputtering threshold energy increases significantly for subsurface recoils, except for those that generate efficient energy transfer to a surface atom by a replacement collision sequence. The implications of the results for the prediction of the mass loss due to sputtering during microanalysis in a FEG STEM are discussed.

Acknowledgements

The authors would like to thank Professor I. P. Jones and Mr B. B. Tang of the University of Birmingham for valuable discussions during the course of collaborative research, and the UK Engineering and Physical Sciences Research Council for provision of financial support.

Notes

‡Present address: Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6158, USA.

†Present address: Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.

†Present address: Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.

Additional information

Notes on contributors

D. J. Bacon *

‡Present address: Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6158, USA. †Present address: Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.