Time-controlled blue-to-red photoluminescence modulation in silicon-rich oxide thin films deposited by HFCVD using SBA-15-based solid precursors

Silicon-rich oxide (SRO) thin films with tunable photoluminescence were deposited by hot-filament chemical vapor deposition (HFCVD) using mesoporous silica SBA-15 and europium-impregnated SBA-15 (SBA-15:Eu) as solid precursors. Unlike conventional gaseous or liquid precursors, the use of chemically engineered mesoporous solids enables a controlled delivery of silicon- and oxygen-containing species, as well as low concentrations of rare-earth dopants, during film growth. Structural characterization of the precursors confirms that europium impregnation preserves the ordered mesoporous framework of SBA-15 while significantly modifying pore accessibility and surface chemistry. The resulting SRO and Eu-modified SRO (SRO:Eu) films exhibit a progressive modulation of their photoluminescence response from the blue to the red spectral region as a function of deposition time and relative film thickness. Photoluminescence analysis reveals the coexistence of multiple overlapping emission bands associated with defect-related and matrix-assisted radiative recombination pathways, whose relative contributions evolve systematically with growth conditions. Although the oxidation state of europium cannot be unambiguously determined from the available data, the optical behavior indicates that, under the present growth conditions, europium does not act as a classical dominant luminescent center. Instead, Eu incorporation perturbs the radiative landscape of the silicon-rich oxide matrix, redistributing the balance between competing recombination channels. These results demonstrate that SBA-15-based solid precursors provide an effective and versatile route for tailoring the structural and optical properties of SRO thin films grown by HFCVD, offering a scalable platform for the development of silicon-compatible photonic materials with tunable luminescence. • Mesoporous SBA-15 and SBA-15:Eu are demonstrated as effective solid precursors for HFCVD growth of SRO thin films. • Europium incorporation modifies pore accessibility and precursor chemistry without collapsing the SBA-15 mesostructure. • SRO:Eu thin films exhibit systematic blue-to-red photoluminescence modulation controlled by deposition time. • Photoluminescence tuning arises from redistribution of radiative channels within an amorphous SiO x matrix. • Precursor-engineered HFCVD enables emission control without changing gas chemistry or dopant concentration.