Fig. 1: Structure, thermodynamics, and spectral properties of HEGS.

a Photo of HEGS samples with varying doping concentrations. b The intensity-interplanar relationship of the HEGS system, derived from the original intensity-diffraction angle relationship from X-ray diffraction measurement. The inset is the TEM micrograph of the HEGS sample. c DSC result of one HEGS sample. When the sample was heated to around 300 °C, a non-reversing endothermic peak was present, accompanying the reversing vitrification process. Isolation of the two processes was accomplished by peak fitting. d The infrared absorption of different samples with a thickness of 3-4 mm. For fused glass, the peak at 2200 cm⁻¹ results from the double-frequency peak of Si-O-Si vibration mode at 1104 cm⁻¹. The peak at 2670 cm⁻¹ results from the double-frequency peak of Si-O-Si vibration mode at 795 cm⁻¹ and the sum-frequency peak of Si-O-Si vibration mode at 1104 cm⁻¹. The peak at 3654 cm⁻¹ is assigned to the O-H due to the adsorption of water on the fused silica. Overtones with higher frequency is unlikely to appear and the allowable overtones or combinations are limited. Hence, the absorption of fused silica glass is weak between 2000 cm⁻¹ and 3800 cm⁻¹