Macromolecular Sample Sputtering by Large Ar and CH4 Clusters: Elucidating Chain Size and Projectile Effects with Molecular Dynamics

This article reports the latest developments of our theoretical studies of gas cluster bombardment of model macromolecular samples using molecular dynamics simulations. Here, we perform a detailed comparison of the effects of the sample molecular weight, the Ar cluster incidence angle (45° vs 0°), and the cluster nature (CH4 vs Ar) on the soft sputtering of polymeric samples. The results of Ar cluster-induced sputtering and fragmentation at 45° incidence for molecular targets with three different molecular weights (282, 1388, and 14002 amu) indicate a pronounced influence of that parameter beyond 1000 amu, which is explained by the extra energy needed to form fragments from longer chains and to overcome mechanical entanglement. An excellent agreement is found between the computed statistics of sputtering and the available experimental data for similar molecular weights. The variance of the sputtering and polymer fragmentation results with changing beam parameters is explained via the microscopic analysis ...