Ge/Si core/shell quantum dots in an alumina matrix: influence of the annealing temperature on the optical properties

Structures with Ge/Si nanoparticles (quantum dots) in an alumina matrix are interesting for researchers due to the combination of two main semiconductors, as well as the use of a matrix with high dielectric permittivity and strong oxygen oxygen–metal bonding. Nanoperiodic multilayer structures in the sequence substrate/Al$_{2}$O$_{3}$/Ge/Si/Al$_{2}$O$_{3}$ $\dots$ Al$_{2}$O$_{3}$ (period – Al$_{2}$O$_{3}$/Ge/Si, the number of periods was up to 20) annealed at different temperatures were prepared in this work. It was shown that nanocrystalline particles of both Ge and Si were observed in the structures after annealing. Nanocrystal sizes and quantity were determined by the thicknesses of deposited layers and the annealing temperatures. The results obtained by various optical techniques indicate a quantum-size effect in the structures, which is confirmed by high-resolution microscopy.