Luminescence of polymorphous SiO2

• Luminescence of polymorphous silicon dioxide was studied.
• Raman spectra are different for quartz, coesite, stishovite, cristobalite and silica glass.
• Luminescence comprises bands of self-trapped exciton and host material defect.
• Luminescence of self-trapped exciton possesses high energetic yield for tetrahedron structured crystals.
• Defect related luminescence observed in silica glass as grown stishovite, coesite and irradiated quartz crystal.

The luminescence of self-trapped exciton (STE) was found and systematically studied in tetrahedron structured silica crystals (α-quartz, coesite, cristobalite) and glass. In octahedron structured stishovite only host material defect luminescence was observed. It strongly resembles luminescence of oxygen deficient silica glass and γ or neutron irradiated α-quartz. The energetic yield of STE luminescence for α-quartz and coesite is about 20% of absorbed energy and about 5(7)% for cristobalite. Two types of STE were found in α-quartz. Two overlapping bands of STEs are located at 2.5–2.7 eV. The model of STE is proposed as Si–O bond rupture, relaxation of created non-bridging oxygen (NBO) with foundation of a bond with bridging oxygen (BO) on opposite side of c or x,y channel. The strength of this bond is responsible for thermal stability of STE. Similar model of STE was ascribed for coesite and cristobalite with difference related to different structure. STE of Silica glass is strongly affected by disordered structure.