Sep 2, 2011
Graphene makes field emission devices flexible and more efficient
Two-dimensional graphene exhibits strong electrical and mechanical stability under high bending deformation, and combining vertically aligned metallic nanowires (NWs) with graphene is expected to enable various flexible devices. Recently, nitrogen-doped carbon nanotubes and ZnO NWs have been grown on reduced graphene. However, most of the previous methods are based on high-temperature processing, and the growth of vertically aligned metallic NWs on graphene has not been demonstrated before.
Researchers from Seoul National University and the Samsung Advanced Institute of Technology, which are both located in Korea, have developed a simple but efficient low-temperature route to prepare metallic NW-graphene (MN-G) hybrid nanostructures for flexible field emission devices.
In the method, a graphene layer is transferred onto an anodic alumina oxide template and vertically aligned gold (Au) NWs are grown on the graphene surface via electrodeposition. This process allows MN-G hybrid nanostructures including various metallic NWs to be prepared with a controlled length and diameter. Also, the technique avoids any high-temperature steps or unconventional lithography procedures, which implies that it can be applied onto versatile substrates including soft materials.
Highly bendable devices
To fabricate completely flexible field emission devices, the MN-G hybrid nanostructures and another graphene layer on a PDMS substrate are configured as a cathode and an anode, respectively. These bendable components allow highly flexible field emission devices to be produced, which enable operation under highly bent conditions.
As shown in the image, the flexible field emission devices exhibit a high emission current density and stable field emission currents even when bent to a radius of curvature of 25 mm. The results indicate that the device forms a stable NW-graphene junction under the bent conditions and that the contact resistance between graphene and NWs was very low. Since the graphene sample does not have any insulating oxide layer on its surface, we can expect a good electrical contact with metallic NWs.
This new strategy for fabricating flexible MN-G hybrid nanostructures suits a number of applications such as bio-chemical sensors, field emission devices, pressure sensors and battery electrodes.
More details can be found in the journal Nanotechnology.
About the author
This study was conducted by research teams based in the Department of Physics and Astronomy at Seoul National University and from the Samsung Advanced Institute of Technology, South Korea. Prof. S Hong is a professor in the Department of Physics and Astronomy and the Department of Biophysics and Chemical Biology at the Seoul National University. His research has been focused on hybrid nano-devices such as hybrid nanoelectronics, nano-biosensors and biomotor-nanowire hybrid nanomechanics. H Kwang is a PhD student in the interdisciplinary Nano-Science and Technology program at the Seoul National University. M Arif is a masters student in the Department of Physics and Astronomy at Seoul National University. David H Seo is a Research Engineer at the Samsung Advanced Institute of Technology. Prof. S Seo is a professor in the Department of Physics at the Sejong University, South Korea. Prof. J Jian is a professor in the Department of Physics at the Xinjiang University, China.