Effects of interlayer roughness on deposition rate and morphology of aerosol-deposited Al2O3 thick films

The influence of the surface roughness of Al2O3 interlayers on the growth of Al2O3 thick films fabricated by an aerosol deposition (AD) process was investigated as an approach to improving the plasma resistance of the films. The Al2O3 interlayer was fabricated by a plasma electrolytic oxide (PEO) method. This method is capable of fabricating films on the entire surface area of 3-dimensional substrates, whereas the AD process has difficulties with depositing films on complex shapes, such as on edges and corners, and inside holes. To prevent degradation of the plasma resistance with increasing working time, the thickness of the Al2O3 interlayer was increased by the PEO method. The surface roughness of the Al2O3 interlayer was increased linearly by increasing the thickness of the Al2O3 interlayer. On Al2O3 interlayers with surface roughness values of more than 1.5 μm (Ra), Al2O3 films were not grown by the AD process. To investigate the effect of the surface roughness of the Al2O3 interlayer on the growth of Al2O3 films on the Al2O3 interlayer, we attempted to deposit Al2O3 films on an Al2O3 interlayer whose surface roughness was decreased from 1.5 μm to 0.8 μm by polishing. As a result, an Al2O3 film of 2.0 μm in thickness was grown by the AD process. These study results support the conclusion that controlling of the surface roughness is the most important factor in aerosol-deposited film growth.