Experimental evidence for a nonparabolic nanoscale interface shift during the dissolution of Ni into bulk Au(111)

Abstract

We report experimental evidence for the violation of the ``diffusional parabolic law'' ($x\ensuremath{\propto}{t}^{0.5}$, where $x$ is the interface shift and $t$ is time) as predicted recently by computer simulation [Z. Erd\'elyi et al., Phys. Rev. B 69, 113407 (2004)] for a binary system with restricted mutual solubility. Using x-ray photoelectron spectroscopy we investigated the shift of the interface between a thin Ni layer (3 nm) deposited under UHV conditions on top of a Au(111) single crystal during its thermally driven dissolution into the Au substrate. From the temporal evolution of the $\mathrm{Ni}\text{\penalty1000-\hskip0pt}2p$ and $\mathrm{Au}\text{\penalty1000-\hskip0pt}4f$ core level intensities at various fixed temperatures, a power law could be extracted for the time dependence of the interface shift $(\ensuremath{\propto}{t}^{{k}_{c}})$ with exponents in the range of 0.6--0.7. Thus, clear experimental evidence is provided that the kinetics of such a shift might differ from the well known parabolic law if restricted to the nanometer scale.