Basic questions related to electron-induced sputtering in the TEM

Although the theory of high-angle elastic scattering of fast electrons is well developed, accurate calculation of the incident-energy threshold and cross section for surface-atom sputtering is hampered by uncertainties in the value of the surface-displacement energy E-d and its angular dependence. We show that reasonable agreement with experiment is achieved by assuming a non-spherical escape potential with E-d=(5/3) E-sub. where E-sub is the sublimation energy. Since field-emission sources and aberration-corrected TEM lenses have become more widespread, sputtering has begun to impose a practical limit to the spatial resolution of microanalysis for some specimens. Sputtering can be delayed by coating the specimen with a thin layer of carbon, or prevented by reducing the incident energy; 60 key should be sufficiently low for most materials. (C) 2009 Elsevier BM. All rights reserved.