1. Formation of Nanoparticle Films via
Hypersonic Particle Deposition
Peter A. Firth, Angelo Delluomo, William J. Firth, and Zachary C. Holman
Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona USA, 85281
1. Introduction
o The functional coatings market was estimated at
$7.75B in 2010 and is projected to expand to $18.4B
by 2019. Much of this growth will be driven by the
development of nanoparticle based coatings.
o Current techniques for forming nanoparticle coatings
face three major challenges that could limit growth:
1) Lack precise control of thickness
2) Lack precise control of porosity
3) Scalability
o Hypersonic Particle Deposition (HPD) is a promising
solution
HPD begins by aerosolizing a nanomaterial using any desired technique, from atomizing a
nanoparticle-laden solution to feeding nanoparticle-precursor gas into a plasma. The aerosolized
nanomaterial enters the HPD system where it is forced through a slit shaped nozzle. As the
nanomaterial passes through the nozzle, it is accelerated to Mach speeds (700 mph) and directed
towards the substrate. The nanomaterial collides with and adheres to the substrate forming a film.
3. Porosity Control
2. Concept
o Advantages
ü Nanomaterial independent
ü Substrate independent
ü No solvent/substrate interactions
ü Precise control of film properties
ü Low temperature
o Challenges
Ø Deposition rate tied to synthesis method
Ø Film adhesion
Ø High vacuum
Ø Material loss
Ø Roll-to-roll integration
4. Thickness Control
The Holman Lab’s HPD system is a completely custom designed
from the chamber body to the automation software. The system is
currently able to deposit films composed of particles either in
solution or synthesized in its plasma chamber.
Slit
shaped
nozzle
Aerosolized
Nanomaterial
Film
Substrate
Film
composed
of
individual
par9cles
Nano-Infused
Textiles
Optical
Coatings
The Holman Lab’s
HPD system fitted
with a custom
designed CCP plasma
chamber for
synthesizing and
modifying
nanoparticles.
5. Current Capabilities
Thermal Barrier
Coatings
Hydrophobic/
Oleophobic
Porosity was determined using a combination of SEM images and Rutherford
backscattering (RBS). RBS spectra of nanoparticle films (like the one on the right) reveal
the number of atoms present in a film of a given thickness. Comparing the number of
atoms determined by RBS to the expected number in a fully dense film of the same
thickness gives an estimate for void fraction.
Very dense(<40% void) nanoparticle
coating formed by impacting particles
at a high velocity
Very porous(>90% void)
nanoparticle coating formed by
impacting particles at a low velocity
Si
(bulk)
Ag
NP
o The porosity of an HPD film is dependent on the particle’s
velocity when it impacts the substrate with a higher velocity
resulting in a more densely packed film.
o Our system offers three independent methods for adjusting the
porosity (nozzle width, pressure, nozzle/substrate separation)
allowing for precise control.
o Flexible control methods allow for a range of film porosities from
40% to 92% without the need to adjust material properties.
Silicon nanoparticles deposited on silicon and glass
substrates (patterned and unpatterned). Color variation
indicates differences in film thickness.
o Film thickness is critical for optical and microelectronic applications.
o Our system controls the deposition rate by adjusting the particle feed/synthesis rate and the
substrate scan speed.
o Our system has proven capable of consistently depositing films as thin as 20 nm and as thick as 1
mm with non-uniformities < 3% over a 24 in2 area.
Silicon nanoparticle RBS
spectra
Film Properties Nanomaterial Characteristics Substrate Characteristics
o Thickness: 20 nm – 1 mm
o Porosity: 38% – 99.5%
o Uniformity: 97%
o Particles synthesized via
plasma or solution methods
o Size: 5 nm to 900 nm
o Materials: Silicon, TiO2,
Silver, Gold
o Size: 150 x 100 mm
o Materials: Silicon, Plastics,
Polyester Fabrics