Research Aims to Grow and Test a Pure, Smooth and Widely Applicable Thin Film for Future Semiconductors

Humans have become spoiled by technology. We expect an endless supply of computers, devices and machines that get endlessly faster and more powerful and efficient. What we often don’t understand are the extreme challenges scientists and engineers must overcome to deliver the continuous technological advances we take for granted.

Scientists have been searching for several years for materials that allow semiconductors to perform well in high-temperature environments needed for national defense, aerospace and energy production.

University of Virginia School of Engineering faculty have carved a niche in developing high-performance materials, such as those that work in high-temperature electronics, and the Defense Advanced Research Projects Agency recently recognized the potential of this expertise with a Young Faculty Award for Jon Ihlefeld, associate professor of materials science and engineering and electrical and computer engineering.

Ihlefeld is one of three UVA faculty to earn the prestigious Young Faculty Award this year. The award is designed for rising stars in junior research positions and provides them support to develop their ideas in areas that will be useful for national security.

Ihlefeld’s research group is working to develop insulating materials for transistors that must perform reliably in high-temperature environments. His group specializes in electronic oxide materials; their thin films increase the efficiency of computer chips and can serve as low-power computer memory.

The Young Faculty Award enables Ihlefeld to prepare and test an insulating material that is universally compatible with many existing and future high-temperature semiconductors used in high-power integrated circuits, light-emitting diodes, high-frequency amplifiers and electronic switches. Ihlefeld’s innovation lies in the method used to prepare the insulating thin film. His fabrication technique offers the possibility of a more pure chemistry and smooth surface that is also more widely applicable than conventional approaches.

“The insulator is the lynchpin for a new class of microelectronics,” Ihlefeld said. “This area of research represents a next big leap for microelectronics. An ultra-thin insulating material, when possessing a specific combination of structural and electronic properties, enables the design of transistors that can be used for high-temperature computing applications.”

Ihlefeld began working with electronic materials as an undergraduate at Iowa State. “I was really interested in semiconductors, and Iowa State offered specializations in both electronic materials and metals.” Whereas most of Ihlefeld’s fellow undergraduates went straight into industry with firms such as John Deere, Maytag and Rockwell-Collins, Ihlefeld set his sights on grad school.

Ihlefeld sought out the faculty member who had most recently finished graduate school to ask for advice. “He directed me to the [Materials Research Society] Bulletin. Each article is written by people who are leaders in the field. He encouraged me to contact authors of articles that I especially liked, to see if they had a position,” Ihlefeld said.

He discovered a group at North Carolina State University that shared his interest in the subfield of ferroelectrics, where he would earn his master’s and doctoral degrees in materials science and engineering.

“Ferroelectrics are a special class of insulators that ‘remember’ which direction the electric field, or voltage, was applied after it is removed,” Ihlefeld explained. “They can also store more charge than most insulators, which makes them useful in the tiny capacitors that allow your cell phone and computer to function.”

Under N.C. State’s auspices, Ihlefeld benefited from research funding provided by the DuPont chemical company. He spent four years developing a stable and useful insulating thin film—less than one micron thick—to advance the integration of capacitors used in electronic displays and printed electronic circuits, for example.

As a post-doc, Ihlefeld joined a research team at Penn State University to work on bismuth iron oxide thin films. “My dissertation and post-doc research projects studied materials that fall within the same family of insulating materials, but with different research aims. DuPont wanted to develop products that could be used in a wide variety of commercial electronics. At Penn State, I pushed the boundaries on very high quality ferroelectric crystals, to better understand their fundamental behavior.” Ihlefeld said. Ihlefeld produced a near-perfect, one-centimeter square thin film of bismuth iron oxide, a material that displays both unusual electronic and magnetic properties at room temperature. It has potential future payoff in low-energy computing and microelectronics.

Ihlefeld’s dissertation and post-doc research gave him a holistic perspective on ferroelectric materials, from applied to basic research. He honed his skills in growing thin films and conducting experiments to tailor materials for easy integration in electronic devices and to explain material behavior in precisely controlled laboratory conditions.

This vantage point led to an invitation to join Sandia National Laboratories, part of the U.S. Department of Energy’s National Nuclear Security Administration, where Ihlefeld could make materials for national needs and help research teams leverage the materials’ fundamental properties. Ihlefeld developed composite materials for infrared filters and grew thin films to improve lithium ion, low-profile batteries.

“The research challenge for batteries was to take a material that would work well in bulk and make it thin. I am able to lead a research team and program in this area because of Sandia,” Ihlefeld said.

Ihlefeld also participated in several projects Sandia refers to as grand challenges, supported by large, interdisciplinary teams and internal investments. “These were fantastic opportunities to collaborate with people throughout the laboratories, to set goals and visions for what we wanted to achieve and hold ourselves accountable for making it happen,” Ihlefeld said.

The rewards and opportunities of working in a national lab were great, but could not move Ihlefeld toward his earliest and ultimate ambition to be a university professor.

“Working at Sandia at that point in my career was probably the best thing that could happen to me. The nature of the problems to be solved helped me further enhance my skills and introduced me to new research areas and research methods within my areas of interest. One limitation at Sandia, however, was the ability to work with and mentor students. I felt that my unique experiences could help me develop a strong research program and that students could benefit from the breadth of fundamental and applied research experience.”

Ihlefeld realized this ambition at UVA Engineering when he applied for a position in multifunctional materials integration. This is a cross cutting research initiative in UVA Engineering that brings together researchers from multiple engineering disciplines to integrate materials with a wide array of functionalities.

“A critical component of the initiative is the ability to design and integrate functional thin film materials with tailored properties on substrates and in devices to enable unprecedented performance in a desired technology. This is of utmost importance in electronic devices and energy storage systems, where materials like ferroelectrics or thin film gate oxides prove critical,” Patrick Hopkins, professor of mechanical and aerospace engineering and past co-director of the multifunctional materials integration initiative, said. 

“There’s a lot of opportunity here; my own graduate advisor told me that hiring good people is the most important thing in running a group, and UVA’s reputation as an outstanding school means that we attract a diverse pool of excellent students,” Ihlefeld said. “I really enjoy working with graduate students; it’s exciting to get them to the point where they can work independently and begin to generate their own ideas and test them in the lab.”

Shelby Fields was the first Ph.D. student to join Ihlefeld’s multifunctional thin film group. “Jon came in with clear ideas of what he wanted to study. He had a lot of energy to get research done,” Fields said.

Ihlefeld anticipated being in the lab as often as his students. Ihlefeld’s hands-on approach attracted Fields, who also embraced the challenge of instrument assembly and calibration.

“Bending metal, testing properly, running gas lines through the lab—if I had been dropped into an ongoing project, I would have missed out on this experience,” Fields said.

Fields also leveraged Ihlefeld’s research at Sandia. “Working with material samples that Jon and his Sandia colleagues had deposited at Sandia, I could immediately characterize and explore their properties without having to grow the samples myself,” he said.

Fields defended his research dissertation proposal last spring. Three other group members are at earlier stages of their research, and two more will join soon.

Fields continues to enjoy the benefits of collaboration with Sandia, completing a research internship at the Laboratories in the fall of 2019. “I share Jon’s appetite for the fundamentals,” Fields said. “I really appreciate the ability to understand the field, to get to know players in adjacent fields, and to keep sight of where our own research fits in the big picture.”

Ihlefeld teaches materials characterization and dielectric materials and is cracking open old textbooks to take his turn teaching the physics of materials. Ihlefeld looks forward to working with undergraduate students who choose to major in materials science and engineering, a new bachelor’s degree program available in spring 2021.

“The electronics that we’ll rely on in the future are currently unknown, but one thing is certain,” he said. “New devices will require integration and processing of materials to achieve unprecedented performance. There is no shortage of exciting research to be done.”