Detection by sputtering of deformed areas hidden under a surface

A sensitive method of visualization by sputtering of deformed areas buried under a surface is developed. The effect of varying the lattice constant and binding-energy of surface atoms of binary disordered alloys on the sputtering of areas deformed by a concentrated load was examined using molecular dynamics. The calculation was carried out for Cu87Sn13, Ni97Fe3 and Fe97Ni3 alloys, which are used for manufacturing of coins and items with marking signs. Experimentally and by MD simulations of energy and angular distributions of sputtered particles, we have shown that the best conditions for detection of deformed areas, buried under a surface, occur in the case of irradiation by inert gas ions of sufficiently large mass (Ar+, Kr+) with energy of 7-10 keV, when the sputtering yield is close to its maximum value. We suggest using an inclined ion beam, near the maximum of the angular dependence of the sputtering coefficient. This leads to reduction of the time necessary for ion irradiation, and to an increase in clarity of the obtained image due to a cumulative effect in the narrow near-surface layers of the target. Using the recommended parameters of sputtering has allowed us to reveal a destroyed image on a bronze coin and images of completely ground off marking numbers on steel objects.