Effect of annealing on optical properties of thin films with β-FeSi2 quantum dots

Reactive deposition epitaxy was used to prepare β-FeSi2 nanodots on a Si(001) surface. The influence of annealing on optical properties has been studied. Annealing increases the particle size and decreases absorption. The indirect optical transition at 0.84–0.89 eV dominates the absorption spectra below 1.3–1.5 eV. The film with smaller nanoparticles exhibits higher absorption with direct optical transition energies in the 1.3–1.5 eV range. It suggests that direct transition is dominant only in small (around 3 nm diameter) β-FeSi2 nanodots. Larger particles are dominated by the indirect optical transition.