Credit: © 2007 AIP

Conventional field-emission cathodes used as electron sources for generating X-rays are made of refractory metals such as tungsten. However, recent studies show that carbon nanofibre (CNF)-based devices have superior properties, such as low field-emission thresholds and high mechanical strength. Fabrication of CNF field emitters (CNF-FEs) on large-area flexible substrates would enable an even wider range of applications, including curved field-emission displays, but the effect of stress on the electrical properties of CNF-FEs is not well understood.

Now, Shu Ping Lau and colleagues1 at Nanyang Technological University, Singapore and Nagoya Institute of Technology, Japan report that stressed CNF-FE devices fabricated on flexible polyimide substrates show no signs of degradation, even after 16 hours. Conical CNF emitters with lengths of ˜0.5–1 µm and diameters of 200–500 nm were grown by Ar ion irradiation of 140-µm-thick polyimide strips coated with carbon films.

CNF emitters were bent into cylindrical structures and the average threshold field was ˜3.65 V µm-1, which is compatible with carbon nanotube devices fabricated on flexible substrates. A ZnS:Ag phosphor-coated polyester sheet was used as an anode to demonstrate an all-plastic flexible field-emission display. The highly adhesive stressed CNFs showed no changes in the threshold voltages, thus highlighting their potential practical applications as field-emission devices in display technology and nanoelectronics.