Fabrication and Characterisation of Silicon Quantum Dots in SiO2/Si3N4 Hybrid Matrix

Si quantum dots in SiO(2)/Si(3)N(4) hybrid matrix on quartz substrates were fabricated by magnetron sputtering of alternating silicon rich oxide and Si(3)N(4) layers followed by different post-deposition anneals. X-ray diffraction results indicate that the average dimension of the Si QDs ranges from 1.6 to 5.2 nm. The size and crystallisation of the Si nanocrystals are dependent on a number of factors, including the annealing condition, the SRO thickness and the Si(3)N(4) barrier thickness, as evidenced in XRD and Raman measurements. In particular, thicker Si(3)N(4) barrier layers seem to be able to suppress the growth of Si nanocrystals more effectively. PL measurements indicate that the apparent bandgap of the samples investigated in this work is in the range 1.12-1.67 eV, which demonstrates the effect of quantum confinement. More interestingly, analysis of the PL data reveals that the PL peak energy does not only depend on the size of the nanocrystals, but also affected by other details of the nanocrystal formation. A simple core-shell model is constructed to illustrate our explanation. These findings offer a preliminary understanding of the nanocrystal growth and radiative recombination processes in this newly synthesized material.