Reflection–absorption infrared investigation of hydrogenated silicon oxide generated by the thermal decomposition of H8Si8O12 clusters

Abstract

Reflection-absorption infrared spectroscopy has been employed to observe Si-H bonds within a model, ultrathin silicon oxide. Upon heating a monolayer of H 8 Si 8 O 12 /Si͑100Ϫ2ϫ1 to 700°C, Si-H bonds as a part of HSiO 3 entities are still detected within the oxide layer after cooling. These fragments appear to be stable to temperatures of at least 850°C. Reversible hydrogen/deuterium exchange for these entities is also directly observed.

The formation of microcrystalline defects on the surface of silica glass arising from mechanochemical processing

“…Destruction and evaporation of such atomic clusters should require more energy. That is why the appearance of a small residual I 85 peak after annealing at 950 • С (in contrast to the effect observed in Nicholson and Zhang 26 ) does not contradict our hypothesis. Perhaps crystalline octahydridooctasilsesquioxane defects can be destroyed at a higher temperature.…”

“…To verify our assumption about the formation of H 8 Si 8 O 12 defects, a ground and deeply‐etched silica plate was annealed at 950°С. The annealing temperature was chosen to be larger than the limit of temperature stability of H 8 Si 8 O 12 , equal to ∼850°С according to Nicholson and Zhang 26 . The dependence of the I 85 height against the annealing duration is shown in Figure 8.…”

“…This observation that some defects were formed close to the surface, while other defects were formed at the bottom of deep cracks, is worth discussion. Note that Nicholson and Zhang 26 described the breaking up of surface oxide layers formed after chemisorption of H 8 Si 8 O 12 molecules on the surface of silicon crystals. The heating of the samples up to 850°С activates a process of evaporation of these layers from the surface.…”

“…The annealing temperature was chosen to be larger than the limit of temperature stability of H 8 Si 8 O 12 , equal to ∼850 • С according to Nicholson and Zhang. 26 The dependence of the I 85 height against the annealing duration is shown in Figure 8. As was expected, the annealing leads to a decrease of the I 85 peak and this can be linked with a reduction in the concentration of octahydridooctasilsesquioxane defects.…”