科研之友
微信
新浪微博
Facebook
分享链接
摘要
Amorphous heavy metal oxide thin films have important technological applications, including multi-layer mirror coatings in instruments such as the Laser Interferometric Gravitational Wave Observatory (EGO). However, the structures of these materials are much less well-known than those of conventional glass-forming oxides. For example, it has not been clear whether films deposited by methods such as ion beam sputtering (IBS) ever pass through a state of local (metastable) thermodynamic equilibrium, and hence could be amenable to modeling by thermodynamic approaches long explored in glass-forming liquid systems. We present new O-17 and Si-29 NMR data on IBS films and sol-gel equivalents in the silica-hafnia and silica-zirconia binary systems. Similar distributions of local structural groups are obtained by different synthesis routes, suggesting that indeed a transient, possibly liquid-like metastable state is reached during film formation. All oxygen species are well-resolved in the spectra and can be readily quantified. Their concentrations are indeed well-predicted by a simple thermodynamic treatment, similar to that applied for decades to binary metal oxide-silica liquids, based on the reaction of bridging oxygens with added "free" metal oxide ions to form non-bridging oxygens.
