Sputtering of organic molecules by clusters, with focus on fullerenes

Abstract

Energetic cluster beam bombardment of organic samples involves a number of physical and chemical effects that are interconnected in a complex manner. In this labyrinth for the scientist's mind, molecular dynamics (MD) simulation constitutes our Ariadne's thread, because it provides the time-resolved microscopic view of the desorption process that is needed to interpret experiments. By combining molecular ion yield and energy distribution measurements with MD simulations, it is possible to explore desorption and ionization from thin organic films and polymers. Recent results show that the overall dynamics and, to a large extent, the details of the cluster-induced sputtering process are well described using a simpler coarse-grain prescription instead of a full atomistic model, allowing us to speed up computations and leap towards larger systems and higher projectile energies. In this article, we first describe some of the characteristic mechanisms of energetic cluster and especially fullerene projectile bombardment of organics. Then, open issues arising from recent experimental investigations are addressed, such as the importance of specific chemical reactions and ionization processes that are outside the scope of the model. Finally, the discussion highlights cases where the predictive nature of the simulations should be used to facilitate the work of experimentalists, such as testing the properties of new cluster projectiles.