UB chemists have found a new way to deposit metal oxides without the compounds in question sustaining damage from the high temperatures required for a chemical reaction between metal and oxygen.
This kind of breakthrough is the science behind building thinner, lighter computers, iPods and other electronic devices, according to Robert L. DeLeon, Ph.D., adjunct associate professor of chemistry.
"We are producing materials that would be in various types of electronic devices - computers or anything that requires chips," DeLeon said. "The idea is to make electronic devices more portable, lighter and faster."
James F. Garvey, Ph.D., professor of chemistry, explains that this is also an enabling device for thin film battery technology.
"Battery technology has not changed since the 1930s; half the weight of the laptop is the weight of the battery, and if one can find a way to make thin batteries, we could then have devices like in Minority Report," Garvey said.
The new technology may also be applied to filming glasses, computer hard drives or other sensitive surfaces. Garvey said the metal oxide thin films might act as simple protective coatings on glasses to make them scratch-proof, or on hard drives making them crash-proof.
This technology can even be used on contact lenses, according to Garvey.
"With our technique, you could easily imagine putting on the same metal oxide and having the contact lens retain its original shape and optical properties without being subjected to high temperature plasma," he said.
Lead author Garvey and co-authors DeLeon and Chi-Tung Chiang, Ph.D., a postdoctoral associate, have developed two methods of producing thin metal oxide films on substrates, based on nearly 15 years of research in the field of materials chemistry.
According to Garvey, nearly a decade ago they created the LAMBD (Laser Assisted Molecular Beam Deposition) method for depositing metal oxides onto substrates. This older process involves a lens focusing the light of an ultraviolet laser onto a tiny spot on a metal rod, thus creating plasma that is three to five times hotter than the surface of the sun. This creates a dense cloud of vaporized metal. Oxygen is then injected into the vaporized metal, which reacts to form metal oxide. Lastly, the metal oxide is sprayed to coat the substrate.
However, companies were dissuaded from using this method by the $500,000 laser needed as part of the project. Recently, chemists have developed a new way of doing the same task with electricity. This new process is called PAMBD (Pulsed Arc Molecular Beam Deposition).
According to Garvey, an electrical discharge between two metal rods is used to create the same 20,000-degree plasma needed to create metal oxides.
"Since we are spraying it, this cools the molecules down. Even though they are coming from very, very hot plasma, by the time they expand into the deposition chamber they cool down to about 80 degrees Kelvin," Garvey said.
The breakthrough is in getting the metal oxide cooled down before coating the substrate.
"One of the problems they have is that a lot of the techniques they use to deposit or coat the substrate with metal oxide require high temperatures and so it damages what they are trying to coat," Garvey said. "We now found that we can coat sensitive substrates and they do not get damaged."
The new PAMBD method provides the same results, yet uses electricity to produce the same hot plasma, to create the same chemical reactions to form metal oxides.
"What we have now done is taken expensive laser light and turned to cheap electricity to do exactly the same thing involving the same idea of a high temperature chemical reactor, which reacts metal with oxygen to form a metal oxide, and then we spray it through a nozzle to cool it down and then can deposit on a substrate," Garvey said.
According to Garvey, the development of a device allowing polymer surfaces to be coated with a metal oxide is an important step for making future devices.
He explained that metal oxides are an important material for the electronics industry. Chips found in iPods and PlayStation Portables, for example, are coated with molecules of metal or metal oxides.
"They make these chips by making thin films of stacked molecules of metals and metal oxides," Garvey said.
The PAMBD method allows for maximum control in how thin or thick the films will be and allows for flexibility in which metals and elements react together to make molecules on demand.
According to DeLeon, this research project is a part of a whole process to make thinner and thinner layers of metal oxides.
"In any electronic device, this technology is present, and the thickness of the films that they have is what makes the computer lighter," DeLeon said. "The thinner you make the films, the smaller you can make the device and the lighter you can make them."
Photo: Courtesy of Laron Fomby
