Visible photoluminescence from Si clusters in γ-irradiated amorphous SiO2

Abstract

Visible photoluminescence (PL) bands around 2 eV were studied in 60Co γ-irradiated (dose<1 MGy) oxygen-deficient-type amorphous SiO2 (a-SiO2) excited by 2–4 eV photons. In addition to the well-known 1.9 eV PL band due to nonbridging oxygen hole centers, another PL band was observed at 2.2 eV when excited by 3.8 eV photons. The intensity of the 2.2 eV band increases with decreasing oxygen partial pressure during the sample preparation. Electron-spin-resonance measurements show that the intensity of the 2.2 eV band is correlated with the concentration of the Eδ′ center, a paramagnetic state of a cluster of silicons. After much higher γ irradiation with a dose up to 10 MGy, a new PL band was induced at 1.75 eV under excitation by 2.5 eV photons, as well as the 1.9 and 2.2 eV PL bands. By comparing its spectral shape and excitation energy with known PL band in Si-implanted a-SiO2, it is suggested that the 1.75 eV band is associated with Si nanocrystals formed from Si clusters in a-SiO2 by the high-dose γ irradiation.

Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials

“…In particular, it results in an increase of the radiative surface states density at the Si-NCs/SiO 2 interface [41,42], as discussed in the previous sections. The shift of the Si-O-Si stretching mode to a lower wavenumber indicates a phase change towards an amorphous (non-stoichiometric silicon oxide) and porous structure [33][34][35][36][37].…”

Photoluminescence band near 2.2 eV in γ-irradiated oxygen-deficient silica glass

“…In a previous article [7], we suggested that this 2.25 PL band is associated with silicon clusters (E 0 d : oxygen deficient defects-clusters with five silicon atoms) in amorphous SiO 2 . In Sample Al, which was manufactured by the Ar plasma method in the presence of a very small amount of oxygen (PO 2 = 1.0%), the center of the sample contained the highest concentration of oxygen vacancies (O 3 SiSiO 3 ).…”

Tin-induced enhancement of photoluminescence and crystal growth in Si-rich silica films

“…However, the PL intensities of the two groups of samples are almost the same at other annealing temperatures. The variations of the PL intensity with the annealing temperature also show no differences: The PL intensity first increases with the annealing temperature and then decreases after reaching the maximum value at 800 1C, because the PL centers of samples here are mainly a-Si and NBOHC defects, which would become very unstable if the annealing temperature is too high (this key temperature is 800 1C in most cases) [9]. The PL intensity increases with the annealing temperature again from around 1000 1C, because a large amount of Si NCs form and begin to dominate the PL.…”