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New technology for simpler, more efficient production of “stubborn” metal and metal oxide thin films

Many metals and their compounds must be made into thin films before they can be used in technological products like electronics, displays, fuel cells, or catalytic applications. “Stubborn” metals, however—which include elements such as platinum, iridium, ruthenium, and tungsten, among others—are very difficult to convert into thin films because they require extremely high temperatures (usually more than 2,000 degrees Celsius) to evaporate.

Now, University of Minnesota Twin Cities College of Science and Engineering researchers have developed a cheaper, safer, and simpler technology that will allow a “stubborn” group of metals and metal oxides to be made into thin films.

The research is published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). The researchers worked with the University of Minnesota’s Technology Commercialization Office to patent the technology and have already garnered interest from industry.

Typically, these metal films are synthesized using techniques such as sputtering and electron beam evaporation. The latter consists of melting and evaporating metals at high temperatures and allowing a film to form on top of wafers. This conventional method is very expensive, uses a lot of energy, and may also be unsafe due to the high voltage used.

The University of Minnesota researchers developed a way to evaporate these metals at significantly lower temperatures—less than 200 degrees Celsius instead of several thousands. By designing and adding organic ligands—combinations of carbon, hydrogen, and oxygen atoms—to the metals, the researchers were able to increase the materials’ vapor pressures substantially, making them easier to evaporate at lower temperatures. Not only is their new technique simpler, but it also makes higher quality materials that are easily scalable.

The ability to make new materials with ease and control is essential to transition into a new era of energy economy.

—Bharat Jalan, senior author

Bringing down the cost and complexity of metal deposition while also allowing for deposition of more complex materials like oxides will play a large role in both industrial and research efforts. Now that depositing these metals like platinum will become easier, we hope to see renewed interest in the more complex materials which contain these stubborn metals.

—William Nunn, first author

In addition to Jalan and Nunn, the research team included University of Minnesota Department of Chemical Engineering and Materials Science grad students Anusha Kamath Manjeshwar, Jin Yue, Tristan K. Truttmann, and postdoctoral researcher Anil Rajapitamahuni.

The research was funded primarily by the US Department of Energy, with additional support from the Air Force Office of Scientific Research and the National Science Foundation.


  • William Nunn, Anusha Kamath Manjeshwar, Jin Yue, Anil Rajapitamahuni, Tristan K. Truttmann, Bharat Jalan (2021) “Novel synthesis approach for “stubborn” metals and metal oxides” Proceedings of the National Academy of Sciences 118 (32) e2105713118 doi: pnas.2105713118


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