Luminescent nanostructures based on Ge nanoparticles embedded in an oxide matrix

Ge nanoparticles embedded in an oxide matrix have been obtained by (a) steam thermal oxidation at 650 °C of polycrystalline SiGe layers and (b) deposition of discontinuous Ge films/SiO2 multilayers by low pressure chemical vapour deposition at 390 °C and thermal annealing at 700 °C. These two approaches are compared in terms of the composition and size of the nanoparticles and the luminescence properties of the structures. In both cases violet luminescence peaking at 3.1 eV is detected. The origin of this emission in both types of structures is the same and it will be related to defects at the interface between the nanocrystalline Ge and the dielectric matrix. Thinking about future applications, the second approach is found to be much more attractive from the technological point of view, even considering that the first one gives a more intense luminescence emission, since the structure can be fabricated in a single-run process; these structures are currently being investigated to improve their luminescence emission.