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

Abstract

During the course of atomic transport in a host material, impurity atoms need to surmount an energy barrier driven by thermodynamic bias or at ultra-low temperatures by quantum tunneling. In the present article we demonstrate using atomistic simulations that at ultra-low temperature transient inter-layer 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 ultra low temperatures. The outlined novel transient atomic exchange mechanism could be of general validity. We find that the source of ultra-low 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 few eV. The mechanism is driven by the local thermalization of the Al(111) surface in a selforganized manner arranged spontaneously by the system without any external stimulus. The core of the short lived thermalized region reaches the local temperature of ∼ 1000 K (including few tens of Al atoms) while the average temperature of the simulation cell is ∼ 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 behaviour is possible in other materials as well.

Anomalous atomic transport in driven systems: Ion-sputtering induced enhanced intermixing and cratering in Pt/Ti

“…Taken together, the present findings and our recent results indicate [15,33,36] that the transient enhanced intermixing in the bulk is more widespread in nature than previously thought.…”

“…The G03 code is well suited for molecular calculations, hence it can be used for checking pair-potentials [33]. We find that the fitted interpolated TB-SMA potential nearly perfectly matches the ab initio one [36] hence we are convinced that the TB-SMA model accurately describes the heteronuclear interaction in the Ti-Pt dimer.…”

“…The detailed description of other technical aspects of the MD simulations are given in Refs. [15,33,37,39,40].…”

“…The parameters of the crosspotential have been obtained by nonlinear least square fitting the interpolated crosspotential given in Ref. [15,33] to ab initio diatomic calculations. The notations used for the parameters are the same as given in Refs.…”

“…There are also a growing number of evidences emerged in the last decades that anomalous nanoscale broadening of interfaces or long-range diffusity tail in the impurity concentration profile occur during ion-irradiation or sputtering [16][17][18][19][20][21]15,[22][23][24][25][26][27][28][29][30][31], sputter deposition and thin film growth [32,33] or cluster burrowing [36]. In these cases it can be shown that the magnitude of diffusivity of impurities is beyond the energy range of the implanted ions or clusters [17,15,36].…”