Growth rate, microstructure and conformality as a function of vapor exposure for zirconia thin films by pulsed-pressure MOCVD

Abstract

Thin solid films of zirconia were deposited on solid and porous substrates over a range of deposition conditions by the pulsed-pressure metalorganic chemical vapor deposition (PP-MOCVD) process. The PP-MOCVD process uses timed injections of a liquid precursor solution through an ultrasonic atomizer into a continuously evacuated reactor. Process variables include solution injection volume, reactor volume, base pressure, peak pressure, and precursor concentration. Solid nickel, co-sintered nickel cermet and [100] P-type silicon were investigated as substrates for a range of deposition conditions. The exposure of the substrate to the precursor vapor was defined using a non-dimensional parameter combining the process parameters other than temperature. Deposits were examined by SEM and XRD. Results showed that PP-MOCVD produces a smooth, thin film that follows substrate contours. High exposure rate results in a higher growth rate, and a thicker film with columnar microstructure that bridges most pores in the porous nickel cermet substrates. The nickel cermet samples were prepared as electrode materials for solid oxide fuel cells (SOFC's). For the first time we demonstrate that arrival rate has a minimal effect on morphology and texture compared to deposition temperature.