Lab talk
Nov 23, 2011
New approach to scalable nano-patterning of graphene
Graphene – an atom-thick, two-dimensional layer of carbon – offers many opportunities to developers thanks to its unique mechanical, electrical and thermal properties. However, intrinsic graphene is a semi-metal or zero-gap semiconductor. Patterning of graphene is therefore important to open up its band gap and broaden its applications as a semiconductor material. Existing patterning techniques are mainly based on lithography processes, but a team from Purdue University and Arizona State University has developed an alternative approach. The researchers use laser ablation-induced shock pressure to punch and pattern graphene film with nanoscale features in an easy, fast and scalable manner.
The researchers from Purdue University patterned a graphene film experimentally using a strong and short laser shock impact, which was generated by confined laser ablation of an ablative layer. A Q-switched Nd:YAG laser with a pulse width of ~7 ns was used. The pressure is controlled by the laser intensity.
Arrays of holes with diameters of 50, 100 and 200 nm were successfully patterned on monolayer graphene films. It was found that the pressure to punch a nanohole (50–200 nm) is only about 1.2–2.5 GPa, although the tensile strength of graphene is about 150 GPa.
Impact model
The team also carried out molecular dynamics (MD) simulations to study the dynamic punching process of graphene. Researchers from Arizona State University used MD to simulate the process of nanopatterning. Round holes with diameters of 100 and 50 nm were first simulated and the results found to be comparable to the experiments.
Graphene patterned with smaller diameters, which is difficult to perform experimentally, were also simulated, including theoretical predictions of the critical breaking pressure and force. The mechanical properties of graphene can then be analysed based on the simulations. This work should be a good supplement to the studies on the mechanical properties of graphene.
Full details including movies of the punching process can be found in the journal Nanotechnology.
About the author
The study was conducted by a team from Purdue University and Arizona State University. Ji Li is a PhD candidate in the School of Industrial Engineering at Purdue University, US. Her research focuses on nano/micro-scale forming of one-dimensional and two-dimensional nanomaterials. Prof. Gary J Cheng is group leader of the Scalable Micro-nanomanufacturing Laboratory, which is part of the School of Industrial Engineering at Purdue University. Dr Rongjun Zhang is a research scientist at Arizona State University (ASU), US, who works on MD simulation of the project. Prof. Hanqing Jiang is an associate professor in the Department of Mechanical and Aerospace Engineering at ASU. His current research interests include the mechanics of stretchable electronics, multi-scale materials modeling and simulation with emphasis on multifield interactions.
