Structural and EELS studies on Doped Carbon Nanostructures for Cold Field Emission

Abstract

Along with the development of cold field emissi on technology, more and more microscopes equipped with cold field emission gun (C-FEG ) are applied in scien tific research. Thanks to the lower working temperature, the service time of emitter has been ex tended. In the meantime, this technology allows to emit electrons from smaller emission radius compared to thermionic emission and Schottky emission [1]. Based on this property, higher curre nt density, higher brightness, be tter special coherence and lower energy distribution of the emission can be expected, wh ich also means that a better electron beam can be obtained [2]. For the further improvement of cold field emission, new emitter materials have been explored. As a rolled-up graphe ne sheet, carbon nanotubes (CNTs) have the similar property, for instance, low work function, high mechanic performan ce, high melting point, high carrier mobility [3-4]. In addition, CNTs have small apex radius curvature for its quasi-one -dimensional character at nanoscale. Therefore, CNTs are capable of working under the operating condition of cold field emission [5]. Furthermore, carbon nanocones are considered as candi date as well [6]. Significant improvements of such kind of carbon nanocones are demonstrated by repl acing the regular tungste n tip in transmission electron microscope [7]. For a higher performance of the cold field emission application, the electronic band structure of carbon nano-object can be modulat ed through the introduction of heteroatoms and a lower work function can be expected [8,9]. Our work is devoted to th e doping of these carbon nanostructures by nitrogen and/or boron, and to the evaluation of these doped carbon nano-objects by a characterization for the cold field emission application.