Influence of porosity and pore size on sputtering of nanoporous structures by low-energy Ar ions: Molecular dynamics study.

Graphical abstract Highlights • Presence of nanosized pores can enhance the sputtering. • Ion irradiation of nanoporous structures can cause the collapse of pores in near-surface layers. • As a result of pore collapse, a continuous solid layer is formed on the material surface. • Excess surface energy per unit volume is a key parameter to determine the probability of pore collapsing. Abstract In this paper we have carried out molecular dynamics simulation of the low-energy Ar ion irradiation of nanoporous homogeneous material with different porosity and pore sizes. Our results demonstrate that in a model with small pores (R pore = 0.8 nm) and relatively low (22%) porosity, the pores at near-surface layers collapsed due to the ion bombardment, whereas in a model with larger pores (R pore = 2.8 nm) and higher (44%) porosity no significant structural changes occurred under the same irradiation conditions. To study thermal stability of porous structures and to reveal the effects of both the pore radius and the porosity on pore collapsing, our nanoporous structures were subjected to gradual heating. The simulation results demonstrate distinct mechanisms of structural changes in the nanoporous materials depending on the value of the excess surface energy per unit volume. [ABSTRACT FROM AUTHOR]