Field emission properties of different forms of carbon

The results of field emission (FE) studies are reported for three different forms of carbon: smooth amorphous carbon (a-C) films with both low and hig h sp(3) content prepared by pulsed-laser deposition (PLD), nanostructured c arbon prepared by hot-filament chemical-vapor deposition (HFCVD), and verti cally aligned carbon nanofibers (VACNFs). The Studies reveal that smooth PL D carbon films are poor field emitters regardless of their sp(3) content. C onditioning of the films, which resulted in films' modification, was requir ed to draw FE current and the emission turn-on fields were relatively high. In contrast, HFCVD carbon films exhibit very good FE properties, including low-emission turn-on fields, relatively high emission site density, and ex cellent durability. Finally, VACNFs also were found to possess quite promis ing FE properties that compete with those of HFCVD films. We believe that t he latter two forms of carbon are among the most promising candidates for u se as cold cathodes in commercial devices. (C) 2001 Elsevier Science Ltd. A ll rights reserved.