FORMATION OF MGO FILMS BY ULTRASONIC SPRAY-PYROLYSIS FROM BETA-DIKETONATE

Chemical vapor deposition (CVD) from an aerosol generated by ultrasoni c atomization was used to grow magnesium oxide films on alumina polycr ystalline substrates. The precursor was a solution of magnesium acetyl acetonate (Mg(acac)(2)) in isopropanol. The decomposition of the salt was studied to determine the CVD temperature range. Thermal analysis o f the salt by thermogravimetry, differential scanning calorimetry and IR and mass spectrometry enabled a decomposition model of the salt to be determined. Above the melting temperature at 265 degrees C, Mg(acac )(2) is no longer stable. The molecule splits giving, on the one hand, a gaseous organic residue and, on the other, a liquid (MgC5H6O2) whic h in turn gives rise to MgO at 450 degrees C. The film presents a smoo th microstructure and a highly preferentially oriented structure with the (200) planes parallel to the substrate surface at a deposition tem perature of about 400 degrees C. The thickness obtained reaches 10 mu m, which represents an effective diffusion barrier on alumina for the deposition of thick films containing alkaline earth elements.