Newswise — WASHINGTON, D.C., Oct. 22, 2018 -- Imagine a coating as hard as a diamond and a fraction the thickness of a human hair. Researchers are exploring new approaches to create resilient thin films that could be used in a variety of electronic applications from cutting tools to the aerospace industry.
During the 65th AVS International Symposium and Exhibition, being held Oct. 21-26, in Long Beach, California, Grzegorz Greczynski will present a new deposition method that improves the thermal and chemical stability of transition-metal nitride (TMN) thin-film layers. The results will be presented during the session entitled New Challenges and Opportunities in Surface Engineering.
Researchers have alloyed TMNs with aluminum to enhance the stress and high-temperature oxidation resistance that make these films ideal for wear protection in high-temperature machining. Following conventional practices, the aluminum often precipitates as a wurtzite-aluminum nitride complex (w-AlN), that lacks the hardness characteristics necessary for mechanical applications.
Greczynski, associate professor at Linköping University, will discuss a new deposition technique that his team, in cooperation with professor Jochen Schneider’s group at RWTH Aachen in Germany, developed that uses two simultaneous plasma sources. One (dc-magnetron sputtering [DCMS]) produces a continuous flux of vanadium atoms to the metal substrate, while the second (high-power impulse magnetron sputtering [HIPIMS]) delivers periodic fluxes of ionized aluminum.
The nitrogen in the carrier gas, consisting of a mixture of nitrogen and argon combines with the aluminum ions and vanadium neutrals forming the thin film on the metal substrate. The key to this deposition method is the application of the susbtrate bias, which is synchronized to the aluminium ion flux.
“With our approach, the vanadium and aluminum are not present in the same volume at the same time,” Greczynski said. “We intentionally separate vanadium from aluminum to overcome the limitations (i.e., w-AlN precipitation) of conventional processing.”
Greczynski and his team used Monte Carlo type simulations (TRIDYN) to better understand the interaction of the Al ions with the VAlN thin-film surface, in particular to calculate the depth that the aluminum ions penetrate into the thin film. By comparing the model results to experimental results, they honed the deposition process.
The research team controlled the depth of aluminum penetration in the film by simply adjusting the amplitude of the synchrounous bias voltage pulse. By increasing their incident energy, the aluminum ions were driven deeper into the film, below the high-mobility surface layer, while creating supersaturated VAlN alloy films.
Aluminum ionization remains the limiting step in this new method. The HIPIMS method only ionizes about 70 percent of the aluminum flux, at best. The remaining 30 percent arrives to the metal substrate as neutrals that do not separate from the vanadium in the film.
Despite the incomplete ionization of aluminum ions, this new deposition method overcomes the limitations of conventional processing and enables unprecedented control over the phase formation and properties of the thin films. According to Greczynski, this deposition method could open the door to new opportunities for scientific endeavors.
“The fact that we can control the crystal structure of these metastable films in such a simple way is exciting,” said Greczynski, “It is nice to see that we change the settings and obtain an immediate effect that makes sense.”
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Presentation 768, “Selectable Phase Formation in Al-based Transition Metal Nitride Films by Controlling Al+ Subplantation depth during HIPIMS Deposition,” by Grzegorz Greczynski, is at 2:20 p.m. PT, Monday, Oct. 22, 2018, in Room 202C at the Long Beach Convention Center, Long Beach, California.
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MORE ABOUT THE AVS 65TH INTERNATIONAL SYMPOSIUM & EXHIBITION
The symposium is being held Oct. 21-26, 2018, in Long Beach, California.
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Founded in 1953, AVS is organized into technical divisions and technical groups that encompass a range of established as well as emerging science and technology areas. There are also regional chapters, international chapters and affiliates, and student chapters that promote communication and networking for professionals and students within a geographical region. AVS is comprised of approximately 4,500 members worldwide.
AVS is a member society of the American Institute of Physics with additional benefits for our members. For more information about AVS, visit our website at http://www.avs.org.
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Meeting Link: 65th AVS International Symposium and Exhibition
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