Structure of amorphous aluminum oxide

Whereas prototypical Al2O3 is not a glass former, amorphous Al2O3 can be formed as thin films through vapor deposition and can serve as a structural model for the Al2O3 glass. The first two-dimensional solid-state NMR experiments for amorphous Al2O3 thin film reveal that four- and five-coordinated species are predominant (95%), while six-coordinated species are minor. Such a species distribution is remarkably similar to what has been predicted theoretically for Al2O3 melts. Upon annealing to 800°C the five-coordinated species becomes negligible, indicating the onset of crystallization of Al2O3.