Uniform coating of TiO2 on high aspect ratio substrates with complex morphology by vertical forced-flow atomic layer deposition

This study reports a novel forced-flow atomic layer deposition (ALD) process in which the precursors are forced to flow vertically through the highly porous substrate. The uniform coating in the interior of the hollow fiber membrane (length: 10 cm) indicates that the precursors are able to permeate through the pores within the membrane. Besides enabling faster processing, the new reactor design also improves precursor utilization efficiency. The new novel ALD reactor equipped with multiple reactors to increase the throughput offers a more uniform coating with good conformality on macroscopically 3-dimensional complex substrates with high aspect ratio. The improvement gained by this new reactor design brings a new research field for coating on 3-dimensional complex porous substrates.