Growth rate and morphology for ceramic films by pulsed-MOCVD

Titania films were deposited on nickel substrates from a dilute solution of titanium isopropoxide (TTIP) in toluene in order to study the growth rate and degree of microstructure control attainable with a metalorganic chemical vapor deposition system called pulsed-MOCVD. This novel system employs pulsed liquid injection with ultrasonic atomization to deliver the precursor to the low-pressure reactor. The film growth rate was studied as a function of temperature and precursor injection rate. An Arrhenius behavior was evident for susceptor temperatures below 500°C. At higher temperatures, the growth rate was nearly equal to the injection rate. Films 45 ±0.1-μm thick were deposited at rates of up to 0.5 ±0.008 μm/min. Two methods were employed for measurement of film growth rate, direct in situ observation of color-fringe evolution and calculation from final film thickness measurements using an optical microscope. The influence of deposition parameters on morphology was studied. The microstructure was characterized using optical and scanning electron microscopy (SEM) and X-ray diffraction (XRD). At temperatures below 500°C the film was dense with small equiaxed crystals. At higher temperatures films were textured and columnar. With the combination of high injection rate and high temperature, fully dense oriented films were produced.