Platinum is added to thermal barrier coatings (TBCs) as it is observed empirically to extend their lifetime, but the mechanism by which Pt acts is unknown. Since Pt has been proposed to alter diffusivities in NiAl, a key component of TBCs, we use first-principles quantum mechanics calculations to investigate atomic level diffusion mechanisms. Here, we examine the effect of Pt on five previously...

Point defects in semiconductors play a decisive role for the functionality of semiconductors. A detailed, quantitative understanding of diffusion and defect reactions of dopants is required for advanced modelling of modern nanometer size electronic devices. With isotope heterostructures which consist of epitaxial layers of isotopically pure and deliberately mixed stable isotopes, we have studie...

A semiempirical interatomic potential for Fe was used to calculate the diffusivity in bcc Fe assuming the vacancy and interstitial mechanisms of self-diffusion. Point-defect concentrations and diffusivities were obtained directly from molecular dynamics MD simulations. It was found that self-diffusion in bcc Fe is controlled by the vacancy mechanism at all temperatures. This result is due to th...

The commonly used partial differential equations for point defect diffusion are reviewed. Special attention is given to the initial conditions of the point defect concentrations. Our numerical simulations clearly show that the assumption of initially equidistributed point defect concentrations at process temperature is justified only for a very special choice of parameters. A more general treat...

Current dopant diffusion theory is based on dopant-point-defect interaction, and assumes that the number of dopant-defect pairs is much smaller than the unpaired dopant concentration. In cases where a large number of excess defects are created from implantation damage, this may no longer be a valid assumption. A new derivation of the dopant and defect equations is presented which is valid for a...