Atomic layer deposition on particles using a fluidized bed reactor with in situ mass spectrometry

A fluidized bed reactor (FBR) was designed and constructed for the delivery of reactive gases to particle surfaces to functionalize particles at large scale using atomic layer deposition (ALD). Nano- and micron-sized particles were effectively fluidized using an inert carrier gas assisted by mechanical agitation of the powder bed. The gas-solid contacting properties of fluidized bed reactors are beneficial for ALD surface reactions, while the frequent solid-solid collisions do not disrupt the self-limiting behavior of ALD reactant gases. Films can be deposited with monolayer control on individual particles of various substrate types, including metals, ceramics and polymers. In situ mass spectrometry was used for real-time monitoring of gaseous product(s) and reactants throughout the ALD reaction. Alumina (Al2O3) ALD on particles demonstrates the process control capabilities of this unique, scalable configuration. The applications of Al2O3 ALD films on particles are widely varying but typically involve core substrate surface passivation, which includes thermal oxidation resistance, photocatalytic activity mitigation and the fabrication of electrically insulative metal particles. Particle functionalization is achievable to nanoscale precision on a wide range of substrate types and sizes with minimal waste of costly ALD precursors and process time.