Lattice Mismatch in Crystalline Nanoparticle Thin Films*

Abstract

For atomic thin films, lattice mismatch during heteroepitaxy leads to an accumulation of strain energy, generally causing the films to irreversibly deform and generate defects. In contrast, more elastically malleable building blocks should be better able to accommodate this mismatch and the resulting strain. Herein, that hypothesis is tested by utilizing DNA-modified nanoparticles as “soft,” programmable atom equivalents (PAEs) to grow a heteroepitaxial colloidal thin film. In heteroepitaxial systems with lattice mismatch, elastic strain energy accumulates within the deposited thin film with the addition of each layer. To explore the energetic stability of a heteroepitaxial PAE thin film, a mathematical model based on mean field approximation was used to calculate theoretical PAE interaction potential energies. The impact of lattice mismatch on PAE thin-film energy was investigated by calculating the potential energy of coherently assembled PAE thin films subjected to various amounts of lattice mismatch strain.