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Near-infrared (NIR) photo- and electroluminescence (PL and EL) of Si nanocrystals buried in Si-rich SiOx, film, and their correlation with the structural phase transformation and the varied oxygen composition of SiOx, are investigated. By detuning the N2O flowing ratio (YN 2 O = [N2O/(N2O + SiH4)] times 100%) from 93% to 80% during plasma-enhanced chemical vapor deposition growth, the oxygen composition ratio of the Si-rich SiOx, can be adjusted from 1.64 to 0.88. The grazing incident X-ray diffraction and X-ray photoelectron spectroscopy spectra indicate that the SiOx, transforms its structural phase from Si + SiO2 isomer to Si + SiO + SiO2 isomer. With O/Si ratio >1.24, the SiOx, matrix becomes SiO2 isomer, whereas the SiOx, structure approaches SiO phase at O/Si ratio that is nearly 1.0. The formation of SiO matrix in SiOx, grown at YN 2 O below 85% reduces the precipitated Si nanocrystal density from 2.8 times 1018 to 7 times 1016 cm-3, and monotonically attenuates the NIR PL by one order of magnitude. Such a structural phase transformation from SiO2 to SiO in SiOx with lower O/Si ratio causes the degradation in EL power conversion efficiency and external quantum efficiency (EQE). Maximum EL power of 0.5 muW and EQE of 0.06% are obtained from MOSLED made on SiOx, with optimized O/Si ratio of 1.24.