Wavenumber cm−1 IR bands Oxide type Absorbance a.u’ Ge Al ° ° ° ° °1110 Si–O asymmetrical stretching vibration [14 ] SiO4 tetrahedra structures [14 ] 0.019 0.14 0.55 0.65 0.69 1080 Si–O–Si stretching vibration of the siloxane groups [15 ] 0.096 0.27 0.27 0.37 0.39 1070 Si–O network stretching vibration [16 ] SiO2 network 0.048 0.14 0.16 0.17 0.17 1050 Si–O vibrational group [17 ] SiO1.5 structures [17 ] 0.038 0.18 0.26 0.30 0.34 1030 Si–O vibrational group [17 ] SiO0.5 structures [17 ] 0.023 0.22 0.26 0.28 0,29 1015 Si–O–Si stretching vibrations of the siloxane groups [15 ] 0.13 0.31 0.37 0.33 0.34 960 Si–OH vibrational group [18 ] 0.09 — — — — 950 Si–OH vibrational group [18 ] 0.04 — — — — 920 Si–OH vibrational group [18 ] 0.027 — — — — 912 Al–OH vibrational group [19 ] — 0.02 0.02 0.026 0.035 900 Al–O vibrational group [19 ] Al2 O3 [17 ] — 0.033 0.026 0.06 0.06 875 Si–OH vibrational group [18 ] — 0.040 0.054 0.1 0.11 870 Ge–O–Ge vibrational group [10 , 20 ] GeO2 0.017 — — — — 860 Si–CH3 rocking vibration [14 , 16 ] 0.037 0.067 0.084 0.11 0.11 852 Si–O asymmetric stretching vibration [14 ] SiO4 tetrahedra structures [14 ] 0.026 — — — — 840 Si–O asymmetric stretching vibration [14 ] SiO4 tetrahedra structures [14 ] 0.026 — — 0.05 0.06 820 Si–O–Si bending vibration [21 ] SiO2 0.015 0.15 0.38 0.51 0.52 815 Si–OH vibrational group [18 ] 0.021 0.13 0.23 0.31 0.33 792 Si–C stretching vibration [15 ] 0.059 0.40 0.30 0.28 0.28 784 Si–O symmetrical stretching vibration [14 ] SiO4 tetrahedra structures [14 ] 0.055 0.18 0.18 0.19 0.19 750 Ge–OH vibrational group [10 , 20 ] 0.033 — — — — 740 Si–O/Si–CH3 vibrational groups [14 , 16 ] 0.019 — — — — 660 Si–O–Ge vibrational group [10 ] — — — — 570 Ge–O–Ge vibrational group [10 , 20 ] GeO2 — — — —