MechSE Assistant Professor van der Zande exploring 2D materials & devices

Meet MNTL's newest faculty researcher: Arend van der Zande

Working at the intersection of mechanical engineering, electronics, and materials science, Assistant Professor Arend van der Zande is investigating the properties of 2-dimensional (2D) materials and building novel devices from them. Naturally stable at only one or two atoms thick, 2D materials are a new, exciting class of nanomaterial that are exceptionally strong, lightweight, flexible, and conduct heat and electricity well.

According to van der Zande, 2D materials such as graphene likely won’t replace silicon entirely, but they are good candidates for flexible or wearable electronics and biosensors. “I’d say what silicon does well—making many, densely packed transistors—is hard to beat,” he said. “I see 2D materials broadening our definition of what electronics and mechanics are, not replacing things that already exist.”

Although graphene may be the most studied of the 2D materials, there are hundreds more that van der Zande, a Mechanical Science & Engineering (MechSE) faculty member, and his students will explore. “The properties of different 2D materials are vastly diverse—some are insulators, some are semiconductors, and some are conductors,” he said. “By mixing and combining the individual monolayers, we can re-engineer any electronic element at nanometer sizes, while nearly maintaining the mechanical strength of the individual monolayers.”

As a graduate student at Cornell University and as a postdoctoral fellow at Columbia University van der Zande and his colleagues made some important contributions to optimizing 2D materials growth, understanding 2D heterostructures, and building optical and nanomechanical devices.

While at Cornell, van der Zande made another important contribution: isolating and engineering the first graphene mechanical membranes, which turned out to be incredibly strong and flexible. By taking advantage of these properties, he and his colleagues then used the graphene membranes to build nanomechanical systems like electrostatically tunable drumhead resonators and impermeable gas membranes.

“Graphene membranes represent the ultimate limit in nanoelectromechanical systems (NEMS),” he explained. “It is impossible to make a membrane that is less than one atom thick.”

Later, van der Zande and Pinshane Huang, who joined the Illinois Materials Science & Engineering faculty this summer, showed that 2D materials like graphene and MoS2 are stitched together by one-dimensional lines of defects.

“When growing large areas of these 2D materials, you get thousands of these grain boundaries stitching together individual crystals like an atomic patchwork quilt,” van der Zande said.  “These defects strongly affect the electrical conductivity, mechanical strength, and optical properties of the materials.”

During his postdoc, van der Zande became fascinated by building devices from 2D heterostructures. “We were motivated by a simple question: what new devices and phenomena can we engineer when we put two different 2D material monolayers together?”

They found that they could easily engineer electronic components like transistors and photodiodes by stacking the appropriate 2D materials on top of each other. By simply changing the relative alignment of the layers, they could drastically tune the electronic structure of the individual layers.

As an Illinois faculty member, van der Zande wants to combine his three interests to start engineering new classes of nanometer-scale optoelectronic and mechanical systems using 2D heterostructures. His student began growing molybdenum disulfide (MoS2), the world’s thinnest semiconductor, in the MNTL cleanrooms this summer as part of a collaboration with ECE Assistant Professor Wenjuan Zhu

While they’ve achieved growth of isolated monolayers of MoS2, van der Zande’s goal is to grow large-scale uniform MoS2 and other 2D materials. This fall he is building a metal-organic chemical vapor deposition (MOCVD) system at MNTL that can produce uniform 2D materials on four-inch wafers. “By being able to reliably and scalably grow arbitrary 2D materials, we can turn this field from a scientific curiosity to a realistic technology.”

van der Zande is excited to be a part of the MNTL community. “Nanoscience is impossible to do by yourself because all the tools and expertise we need are beyond any one professor’s budget,” he said. “Being in a facility like MNTL makes a huge difference. The well-developed facilities and easy-to-use shared tools that are available influenced my decision to come here. I am also really excited to get to collaborate with all of the world class scientists working here.”