Powerful electron emitters: graphene-coated nanotubes
doi:10.1038/nindia.2015.96 Published online 24 July 2015
Researchers have synthesized three-dimensional arrays of titanium oxide nanotubes coated with reduced graphene oxide that could potentially be used as electron sources in electronic devices such as microwave amplifiers, parallel-electron-beam microscopes and flat-panel displays1.
When embedded in electronic devices, nanomaterial-based electron sources exhibit field electron emission in which electrons are extracted from semiconducting materials by applying a strong electric field.
The researchers synthesized vertically aligned titanium oxide nanotubes on a titanium substrate and coated them with reduced graphene oxide. They then explored the field electron emission properties of the graphene-coated nanotubes in the presence of external electric fields and compared them with those of commercial nanomaterials.
They found that while the emission current density increased exponentially with increasing electric field strength for all the samples, the graphene-coated nanotubes exhibited the highest current density.
The scientists attribute this enhanced current density to the presence of a large number of delocalized electrons on the surface of reduced graphene oxide, which act as electron injection carriers. At 230 volts, the nanotubes showed stable emission current for more than 2 hours at a current density of 80 milliamperes.
“These graphene-coated nanotubes could potentially be used to develop highly efficient electron sources for stable and ultralow-turn-on field-emission devices,” says Bipin Kumar Gupta, one of the researchers.
1. Agrawal, Y. et al. High-performance stable field emission with ultralow turn on voltage from rGO conformal coated TiO2 nanotubes 3D arrays. Sci. Rep. 5, 11612 (2015)