Single layer of silicon quantum dots in silicon oxide matrix: Investigation of forming gas hydrogenation on photoluminescence properties and study of the composition of silicon rich oxide layers

Structures consisting of a single layer of silicon quantum dots in a SiO2 matrix show interesting optoelectronic properties and potential use as energy selective filters, which are a crucial component for the realization of the hot carrier solar cell. In this work single layer silicon quantum dots in SiO2 have been realized using a magnetron sputtering technique. Quantum dots are formed by annealing of a silicon rich oxide layer deposited between a thermally grown SiO2 layer and a sputtered SiO2 layer. The effects of a forming gas post-hydrogenation process on the photoluminescence of the single layer of quantum dots have been investigated in order to understand the photoluminescence mechanism. It was found that for sputtered silicon quantum dots in SiO2 matrix the photoemission mechanisms are primarily due to quantum confinement and does not strongly rely on matrix defects. In addition, physical and optical properties of several thick silicon rich oxide layers, with different chemical compositions, have been investigated in order to optimize the stoichiometry of silicon rich oxide in the single layers.

► Photoluminescence mechanism in sputtered single layers of silicon quantum dots in SiO2 matrix structures is mostly related to quantum confinement.
► Defects at silicon–SiO2 interface have an active role in the photoluminescence process, but only in creating non-radiative recombination centers and not in generating any additional radiative path for confined excitons.
► Silicon/oxygen atomic ratio of around 1:1 allows for controlling the average size of the silicon quantum dots between two SiO2 barriers by controlling the thickness of the silicon rich oxide layers.