Materials scientist Joshua Robinson looks inside a chemical vapor deposition furnace, which is used to make two-dimensional materials.
PENNSYLVANIA, US: Joshua Robinson recalls the day in 2006 when he learned of a material that is, for all practical purposes, two-dimensional.
At the time, he was a post-doctoral researcher at the Naval Research Laboratory in Washington, DC. His advisor, Eric Snow, was raving about graphene, a newly isolated form of carbon. A cousin of the widely known buckminsterfullerene (or “buckyballs”) and carbon nanotubes, graphene was a flat sheet only one carbon atom thick.
The atoms were linked together in a six-sided, chicken-wire pattern, forming a lattice with astonishing properties. It was flexible, transparent, stronger than steel and conducted electricity and heat better than anything. In short, carbon acted like an entirely new material.
Graphene became known as the first two-dimensional, or monolayer, material. Indeed, at one-third of a billionth of a metre thick, it’s as close to two-dimensional as a tangible object can get. Graphene is 300,000 times thinner than common printer paper.
Robinson was in an ideal position to recognize the importance of two-dimensional (2D) materials. He was working with carbon nanotubes, adapting them to detect minute amounts of airborne substances such as those given off by chemical weapons and explosive devices.
“Graphene was simply an unzipped nanotube,” said Robinson, who is now an assistant professor and Corning faculty fellow in the department of materials science and engineering, Penn State.
Stumbling blocks
Scientists, engineers and investors around the world became excited by graphene, especially its potential to revolutionize electronics.
But the transition from discovery to practical application has turned out to be not so easy. Although materials scientists could create a variety of new 2D materials using other elements and compounds, they could not always predict what properties those materials would have. The tiny or even microscopic bits of monolayer were hard to manipulate and analyze—and impossible to make on an industrial scale.
What the field needed was a deeper understanding of 2D materials and their weird properties. To take on this challenge, in 2013 Penn State’s Materials Research Institute started the center for two dimensional and layered materials (2DLM).
The centre brings together about 50 faculty, postdoctoral researchers and students from Penn State and other institutions around the country. It is the first research center to focus not just on graphene but “beyond graphene,” according to Robinson, the centre’s associate director.
Work at the centre addresses several broad themes. Scientists have made new monolayer materials by combining a variety of elements, such as tungsten or molybdenum with sulfur, gallium or silicon with selenium and boron with nitrogen.
Improved techniques for studying 2D materials have made it easier to predict which compounds will form monolayers and how they might behave in that form.
© The Pennsylvania State University News