Exploring the Energetic Deposition of Pentacene on Pentacene through Molecular Dynamics Simulations

We use molecular dynamics simulations to explore in detail the factors affecting the behavior of an incident pentacene molecule colliding with the pentacene (010) step edge. We examine the effect of molecular orientation in conjunction with incident kinetic energy ( E i ) and angle (θ i ) of the incoming molecule and proximity of the collision of the incoming molecule to the step edge in determining the relative contributions of fundamental mechanisms such as insertion, ejection, and interlayer transport. We find that to maximize 2D growth through experimentally controllable parameters, E i and θ i, the molecular orientation within the beam must be controlled. For θ i = 0°, when the momentum of the incident molecule is aligned along the long axis of the molecule, downward interlayer transport of the incident molecule is dominant for all hyperthermal energies. When the molecular orientation is random, higher energies must be employed to achieve the same degree of downward interlayer transport. For nonzero values of θ i, the mechanism for 2D growth moves away from direct insertions, thus reducing the bias on molecular orientation.