Vibrational Spectra of Vapor-Deposited Binary Borosilicate Glasses

Abstract

Room temperature infrared absorption spectra in the range 4000–250 cm−1 of binary borosilicate thin glass films deposited by reacting argon-diluted SiH4–B2H6–O2 mixtures on heated silicon substrates at 300–400°C have been obtained throughout the composition range. Spectra of the end components are found to be in good agreement with those of vitreous SiO2 and B2O3 prepared from the liquid state. The band shapes, intensities, and frequencies of maximum absorption of the B–O stretching mode and the Si–O stretching mode have been studied as a function of composition. At constant composition the shape of the former band is found to be dependent on the substrate temperature during deposition. Insight into the ``mixing'' nature of these vapor-deposited glassy solids has been obtained from an analysis of the spectral distribution of Si–O–Si, B–O–B, and B–O–Si bonds as a function of composition. A new band at 670 cm−1 not previously reported in literature, has tentatively been assigned to a bond bending mode of the B–O–Si centers in the borosilicate structure.