Kinetics of the Amorphous →γ→α Transformations in Aluminum Oxide: Effect of Crystallographic Orientation

摘要

Time. resolved reflectivity (TRR) measurements have been used to determine the growth kinetics of both the amor- phous-to-γ-phase and the γ-to-or phase transformations of alumina films that have been deposited on (0001), (1210), and (0112) sapphire substrates. The activation energies for the amorphous-to-γ-phase and γ-to-α transformations re- spectively are 4.5 and 5.2 eV, irrespective of the crystallo- graphic orientation of the underlying sapphire substrate. For both transformations, the relative transformation rates seem to reflect the symmetry of the sapphire substrates, with the fastest kinetics being on the lowest symmetry ori- entation and slowest kinetics being on the highest symmetry orientation. These relative rates are attributed to the dif- ferences in step mobility on the different substrate orien- tations.