Effects of Si-rich oxide layer stoichiometry on the structural and optical properties of Si QD/SiO₂ multilayer films

The effects of the stoichiometry of the Si-rich oxide (SRO) layer, O/Si ratio, on the structural and optical properties of SRO/SiO₂ multilayer films were investigated in this work. SRO/SiO₂ multilayer films with different O/Si ratios were grown by a co-sputtering technique, and Si quantum dots (QDs) were formed with post-deposition annealing. By transmission electron microscopy (TEM) and glancing incidence x-ray diffraction (GIXRD), it was found that the Si QD size decreases with increases in O/Si ratio. The photoluminescence (PL) spectrum varies with the O/Si ratio in band position, shape and intensity. In addition, it was observed that the absorption edge blue-shifts with increases in the O/Si ratio. The change in the absorption edge is consistent with strengthening quantum confinement effects in Si QDs, as indicated by TEM and GIXRD. The optical properties were also investigated by 2D photoluminescence excitation (2D-PLE) and lifetime measurements. The origin of emission and absorption is discussed based on the absorption, PL, 2D-PLE and decay time measurements.