Structure of amorphous aluminum oxide.

Whereas prototypical Al(2)O(3) is not a glass former, amorphous Al(2)O(3) can be formed as thin films through vapor deposition and can serve as a structural model for the Al(2)O(3) glass. The first two-dimensional solid-state NMR experiments for amorphous Al(2)O(3) 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 Al(2)O(3) melts. Upon annealing to 800 degrees C the five-coordinated species becomes negligible, indicating the onset of crystallization of Al(2)O(3).