Structural characteristics of Al2O3 thin films prepared by spray pyrolysis

The crystalline and structural characteristics of aluminium oxide (Al2O3) thin films deposited by ultrasonic spray pyrolysis have been analysed using conventional and high resolution transmission electron microscopy. The aluminium oxide films were deposited on silicon (100) wafers, using a solution of aluminium acetylacetonate in dimethylformamide. The films were deposited with and without the addition of water mist generated in parallel to the spraying solution. The substrate temperatures during deposition of the films were in the range of 500-650degreesC. The results indicate that the thin films deposited without water mist have an amorphous structure, while those films deposited with the addition of water mist show a two-face nature, formed by small crystallites embedded in an amorphous matrix. The crystalline phase has been determined, through the indexing of the electron diffraction patterns. It is found that it corresponds to 5Al(2)O(3) . H2O in a Tohdite hexagonal structure with unit cell lattice constants a = 5.575 Angstrom and c = 8.76 Angstrom.