IN-SITU TRANSMISSION ELECTRON-MICROSCOPY CRYSTALLIZATION STUDIES OF SOL-GEL-DERIVED BARIUM-TITANATE THIN-FILMS

Barium titanate (BaTiO3) thin films that were derived from methoxyprop oxide precursors were deposited onto (100) Si, Pt/Ti/SiO2/(100) Si, an d molecular-beam-epitaxy-grown (MBE-grown) (100) BaTiO3 on (100) Si su bstrates by spin coating. The crystallization behavior of the amorphou s-gel films was characterized using in-situ transmission electron micr oscopy heating experiments, glancing-angle X-ray diffraction, and diff erential thermal analysis/thermogravimetric analysis. Amorphous-gel fi lms crystallized at a temperature of similar to 600 degrees C to an in termediate nanoscale (5-10 nm) barium titanium carbonate phase, presum ably BaTiO2CO3, that subsequently transformed to nanocrystalline (20-6 0 nn) BaTiO3. Random nucleation in the bulk of the gel film was observ ed on all substrates, In addition, oriented growth of BaTiO3 was concu rrently observed on MBE-grown BaTiO3 on (100) Si. High-temperature dec omposition of the intermediate carbonate phase contributed to nanomete r-scale residual porosity in the films. High concentrations of water o f hydrolysis inhibited the formation of the intermediate carbonate pha se; however, these sols precipitated and were not suitable for spin co ating.