Island-type growth of Au-Pt heterodimers: direct visualization of misfit dislocations and strain-relief mechanisms

Abstract

Structural and analytical characterization related to the formation mechanism of Au-Pt heterodimers from polyhedral Pt nanocrystals is reported. The observation of specific lattice strain effects and the emergence of misfit dislocations point to the relevance of the Stranski-Krastanov growth mode as a means of explaining the previously reported dimerisation reaction between Au and Pt. Two size-dependent strain relief mechanisms were identified. For dimers grown from 4.7 nm seeds, the mechanism is related to bulk lattice strain accumulation at {111} planes along with lattice relaxation effects on other crystalline planes. However, for dimers grown from 11.2 nm seed sizes, the formation of misfit dislocations proved to be a highly efficient mechanism by which to release interface mismatch strain. Nanoscale chemical mapping at Au-Pt interfaces also revealed Au-Pt alloying to be unlikely under the mild temperature conditions employed in this work for Au-Pt heterodimer synthesis.