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University at Buffalo chemists have developed a novel way to grow
chemically pure, zinc oxide thin films characterized by dense,
bristle-like nanostructures and a new method for depositing them on
temperature-sensitive substrates, including polymers, plastics and
The research, published online recently in the Journal of Physical
Chemistry, may make possible the deposition of versatile zinc oxide
films onto flexible surfaces, enabling the development of more
efficient solar cells, liquid-crystal displays, chemical sensors and
High-quality zinc oxide thin films are versatile and can be
fabricated into many shapes, including films, nanorods and
nanoparticles. However, there is a drawback: They usually are deposited
at high temperatures, which can damage or even melt the substrate they
"That makes it impossible to coat plastic, a hard drive, an
electronic device or even contact lenses since the deposition process
damages the underlying surface," Garvey said.
By contrast, the UB researchers have developed a technique in which
the metal oxide molecules are cool enough to safely coat
The UB researchers grow the thin films by first reacting zinc metal
and oxygen in the presence of a high power, electrical arc discharge.
The method they developed, called Pulsed Arc Molecular Beam
Deposition (PAMBD), strikes a discharge between two pure zinc rods.
"This lightening-like discharge creates a bright, blue plasma five
times hotter than the surface of the sun," Garvey said.
At these high temperatures, the pure zinc metal is vaporized and
reacts completely with an oxygen gas pulse to create chemically zinc
The gaseous zinc oxide is then sprayed through a tiny aperture, a
process that results in cooling the expanding gas down to about 50
degrees Kelvin, he explained, allowing the beam of now cold metal
oxides to safely coat even the most temperature-sensitive surfaces.
"This is an enabling technology that will allow for the deposition
of thin films on batteries, credit cards, on any flexible surface you
have," Garvey said, adding that the UB process can use any metal and a
wide array of different metal oxides can be produced easily.
"Since it is a pulsed technique, the thickness of the resulting
films can be precisely controlled," he noted. "In this way, our PAMBD
source is really a high-temperature chemical reactor that generates
metal oxide molecules on demand and then rapidly cools them down for
subsequent coating of any surface."
The chemists now are working with researchers in the UB Department
of Physics to use the thin films and the deposition technique to create
nanorods and spintronic devices.
In addition to Garvey, co-authors on the paper are Chi-Tung Chiang,
Ph.D., post-doctoral associate, and Robert L. DeLeon, Ph.D., adjunct
associate professor, both in the Department of Chemistry in the UB
College of Arts and Sciences.
The research was funded by the Missile Defense Agency of the U.S. Department of Defense.
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