Self-organized transient facilitated atomic transport in Pt/Al(111)

During the course of atomic transport in a host material, impurity atoms need to surmount an energy barrier driven by thermodynamic bias or at ultralow temperatures by quantum tunneling. In the present article, we demonstrate using atomistic simulations that at ultralow temperature, transient interlayer atomic transport is also possible without tunneling when the Pt/Al(111) impurity/host system self-organizes itself spontaneously into an intermixed configuration. No such extremely fast athermal concerted process has been reported before at ultralow temperatures. The outlined novel transient atomic exchange mechanism could be of general validity. We find that the source of ultralow temperature heavy particle barrier crossing is intrinsic and no external bias is necessary for atomic intermixing and surface alloying in Pt/Al, although the dynamic barrier height is a few eV. The mechanism is driven by the local thermalization of the Al(111) surface in a self-organized manner arranged spontaneously by the system without any external stimulus. The core of the short lived thermalized region reaches the local temperature of approximately 1000 K (including a few tens of Al atoms), while the average temperature of the simulation cell is approximately 3 K. The transient facilitated intermixing process also takes place with repulsive impurity-host interaction potential leading to negative atomic mobility; hence, the atomic injection is largely independent of the strength of the impurity-surface interaction. We predict that similar exotic behavior is possible in other materials as well.