Biomedical Engineering Reference
In-Depth Information
8
Ceramic ultra-thin coatings using atomic layer
deposition
X. LIANG, D. M. KING andA. W. WEIMER,
University of Colorado, USA
Abstract: Ultra-thin films can be coated on primary fine particles without
significant aggregation by atomic layer deposition (ALD) in a fluidized
bed reactor. Precursor doses can be delivered to the bed of particles
sequentially and, in most cases, can be utilized at nearly 100% efficiency
without precursor breakthrough and loss, with the assistance of an in-
line downstream mass spectrometer. A multitude of applications can be
addressed in a competitive fashion using fine particles that have been
surface-modified using ALD in scalable, high-throughput unit operations.
Several examples of the applications of conformal ALD coatings have
been discussed, including oxidation-resistant metals or ceramics, coatings
that enable biomedical applications including tissue engineering, and
corrosion-resistant particles for next-generation batteries, capacitors or
fuel cells. It is expected that the technology of thin film coating by
particle ALD will play a major role in the field of advanced materials.
Key words: atomic layer deposition (ALD), particles, ultra-thin coating,
ceramic, fluidized bed reactor.
8.1
Introduction
A thin film is defined as a layer of material of thickness ranging from
fractions of a nanometer to several micrometers. The thickness of an ultra-
thin film is in the range of several nanometers. Ceramic materials (e.g.
alumina, zirconia, and silicon carbide) are well known for their refractory
characteristics and outstanding mechanical properties. Ceramic thin films
can be deposited onto bulk materials (substrates) to achieve properties not
easily attainable or unattainable by modifying the bulk substrates alone.
