Transmission electron microscopy study on FeSi₂ nanoparticles synthesized by electron-beam evaporation

We have synthesized epitaxially grown iron disilicide (FeSi₂) nanoparticles using an electron-beam evaporation technique and characterized them by transmission electron microscopy (TEM). An Fe film was deposited on a Si(100) substrate, followed by thermal annealing at 1073 K for 2 h. It was found that epitaxially grown nanoparticles with an average size of ∼ 10 nm were formed just beneath the Si surface, suggesting that the deposited Fe atoms diffuse into the substrate. Every single phase of nanoparticles was examined in detail by TEM observation, nanobeam electron diffraction, and energy-dispersive x-ray spectroscopy. Plan-view and cross-sectional TEM observations revealed that these nanoparticles consist of α-, α-, and γ-FeSi ₂. It was found that the morphology of nanoparticles is closely related to the phases. The α and β phases consist of angled hemisphere and asymmetric triangle-shaped nanoparticles, respectively, while the γ phase consists of hemispherical or columnar-shaped nanoparticles. These particle morphologies are discussed with respect to the lattice mismatches between the particles and the matrix.