Pentacene is currently the standard bearer in the expanding field of organic semiconductors due to its relatively high electrical mobilities (rivalling amorphous silicon) and low production costs.  One of the most successful methods of producing flat, ordered, thin films of pentacene is hyperthermal deposition. A simplistic view of hyperthermal deposition treats the deposition “event” or collision separately to longer timescale diffusional/thermal processes. The local effects of the collision are typically on the order of pico-seconds whereas thermal diffusion is a continuous process occurring over the lifetime of the film. In effect the deposition events are instantaneously altering the initial configuration in which the long term processes are taking place but not altering their intrinsic rates due to a rapid thermal equilibration.

We perform a statistical study of the collision event of an incident pentacene molecule in the proximity of a pentacene(010) step edge to relate molecular scale processes to experimentally observable data and features such as adsorption probabilities and AFM morphologies. Previous examples of this approach include a study of the trapping dynamics of ethane molecules on the Si(100) surface at comparable incident energies using empirical potentials.

We use the non-reactive empirical MM3 potential to model the collision of pentacene molecules in the proximity of a pentacene(010) step edge using molecular dynamics. The MM3 potential was used because it is known to accurately model organic molecules in both gaseous and crystalline forms and because of it's transferability to other organic molecules of interest. We show the process of hyper-thermal deposition of pentacene molecules to be sensitive to all variables studied, namely incident energy, incident angle, orientation upon impact and point of impact (in relation to a step edge) and quantified these effects. We have observed direct insertion events at energies of 1eV and above and the subsequent interstitials which are formed in the crystal.  The sticking probabilities calculated are in good agreement with experimental values.