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Abstract: A multilayered Si nanocrystal-doped SiO2/Si (or Si-nc:SiO2/Si) sample structure is studied to acquire strong photoluminescence (PL) emission of Si via modulating excess Si concentration. The Si-nc:SiO2 results from SiO thin film after thermal annealing. The total thickness of SiO layer remains 150nm, and is partitioned equally into a number of sublayers (N =3, 5, 10, or 30) by Si interlayers. For each N-layered sample, a maximal PL intensity of Si can be obtained via optimizing the thickness of Si interlayer (or d Si). This maximal PL intensity varies with N, but the ratio of Si to O is nearly a constant. The brightest sample is found to be that of N =10 and d Si =1nm, whose PL intensity is ∼5 times that of N =1 without additional Si doping, and ∼2.5 times that of Si-nc:SiO2 prepared by co-evaporating of SiO and Si at the same optimized ratio of Si to O. Discussions are made based on PL, TEM, EDX and reflectance measurements. [Copyright &y& Elsevier]

Abstract: Si quantum dots (QDs) embedded in SiO2 can be normally prepared by thermal annealing of SiO x (x <2) thin film at 1100°C in an inert gas atmosphere. In this work, the SiO x thin film was firstly subjected to a rapid irradiation of CO2 laser in a dot by dot scanning mode, a process termed as pre-annealing, and then thermally annealed at 1100°C for 1h as usual. The photoluminescence (PL) intensity of Si QD was found to be enhanced after such pre-annealing treatment. This PL enhancement is not due to the additional thermal budget offered by laser for phase separation, but attributed to the production of extra nucleation sites for Si dots within SiO x by laser irradiation, which facilitates the formation of extra Si QDs during the subsequent thermal annealing. [Copyright &y& Elsevier]

Abstract: We report the evolution of photoluminescence (PL) of Si nanocrystals (nc-Si) embedded in a matrix of SiO2 during Ar+ ion bombardment. The integrated intensity of nc-Si PL falls down drastically before the Ar+ ion fluence of 1015 ionscm−2, and then decreases slowly with the increasing ion fluence. At the meantime, the PL peak position blueshifts steadily before the fluence of 1015 ionscm−2, and then changes in an oscillatory manner. Also it is found that the nc-Si PL of the Ar+-irradiated sample can be partly recovered after annealing at 800°C in nitrogen, but can be almost totally recovered after annealing in oxygen. The results confirm that the ion irradiation-induced defects are made up of oxygen vacancies, which absorb light strongly. The oscillatory peak shift of nc-Si can be related to a size-distance distribution of nc-Si in SiO2. [Copyright &y& Elsevier]