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$2 Million NSF Grant Funds New Materials Research Collaboration

August 11, 2014

$2 Million NSF Grant Funds New Materials Research Collaboration

Joshua Goldberger, assistant professor, chemistry and biochemistry, is principal investigator (PI) on a $2 million project funded by the National Science Foundation’s Division of Emerging Frontiers in Research and Innovation (EFRI). Joseph Heremans, professor, mechanical and aerospace engineering; and physics, is co-PI.

The four-year study, “Enhancing Electronic and Thermal Properties in Epitopotaxial Ge/Sn Graphane Heterostructures,” looks at controlling and modulating the thermal conductance and thermoelectric properties of germanium and tin by manipulating the materials’ thermal properties on the atomic level.

“Our focus,” Goldberger said, “is to create and understand a new class of materials. These two-dimensional (2D) derivatives of germanium and tin, in which the germanium and tin atoms are bonded in a puckered honeycomb network, feature an additional surface terminating group bonded—alternatingly—above and below every atom.

“By manipulating and controlling the bond on the surface, we can profoundly affect the properties of the honeycomb network, including how it conducts heat. Research such as this pushes the study of heat transport to the atomic-size scale.”

The work also is expected to net new engineering tools for thermal processes including the control of heat flows. Heremans said, “That's both enticing and compelling when you realize that roughly 93 percent of the energy we use comes from thermal processes.”

Goldberger’s expertise in constructing synthetic chemicals at the atomic-size is critical to the research team’s ability to verify, predict and establish how the bonded mechanisms might very well become the next generation of electronic and thermoelectric devices.

Actually, an undergraduate researcher in Goldberger's lab—chemistry major Elisabeth Bianco—first created a single layer of germanium atoms terminated with hydrogen atoms. The crystalline version of the material is known as germanane.

Those efforts by the lone chemist among the six other finalists made big news in October 2012, when she won a national nanoscience and nanoengineering competition.

The work of Bianco, now a graduate student at Rice University, has led to further research of the ultrathin material by five of the most senior researchers in the fields of measurements and calculations.

A paper written by Goldberger and Bianco about the creation of germanane was published by the journal ACS Nano last year.

Goldberger said, “There’s been a lot interest in understanding the properties of materials that are a single atom in thickness. What's known about these materials is that they are greatly dependent upon what's around them. When you measure a single atom-thick material, you're not just measuring it, you're measuring everything around it. This can lead to numerous advantages in our understanding, in controlling its behavior and in creating the useful properties we want.

“What's unique about these germanium and tin systems or structures is that these structures are almost exactly the same as graphene. By controlling the bond between germanium or tin and their immediate neighbors—you profoundly affect the properties of the material—how heat and electricity propel through it.

“So while these are indeed two of the most well-known materials associated with the foundation of electronics, they appear to still hold great promise for the future.”

In addition to Heremans, other co-PI’s are Ohio State alumnus David Cahill, professor of materials science and engineering at the University of Illinois, Urbana-Champaign; David Broido, professor of physics at Boston College; and Li Shi, professor of mechanical engineering at the University of Texas -Austin. Natalio Mingo, a senior scientist at CEA-Grenoble, also is a study participant.

—Sandi Rutkowski

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