Electro-optical analysis in determining the field emission characteristics of carbon nanofibers on an acute tip substrate

• Published in: Diamond and related materials 2012-09, Vol.29, p.23-28
• Main Authors: Shimoi, Norihiro, Tanaka, Yasumitsu
• Format: Article
• Language: English
• Subjects: Apex angle; Carbon fibers; Carbon nanofiber; Computer simulation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Convergence; Cross-disciplinary physics: materials science; rheology; Devices; Divergence angle; Electro-optics; Electron and ion emission by liquids and solids; impact phenomena; Electron field emission; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Field emission; Field emission, ionization, evaporation, and desorption; Finite element method; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Palladium; Physics; Surface and interface electron states; Surface charge method; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tip substrate
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2012.07.001

The shape of an acute tungsten (W) tip substrate coated with palladium (Pd) and carbon nanofibers (CNFs) was optimized in order to generate efficient field emission (FE) currents. By adjusting the apex angle of the tip, we succeeded in controlling the FE properties and electron beam convergence. When the apex angle was close to 50º, a narrow convergence of electron beams was observed. By employing an original computation tool based on the surface charge method, we conducted a numerical analysis of the convergence mechanism of the FE device; this was dependent on FE properties, and displayed its maximum around the same apex angle. By simulating the electrical field distribution above the CNF, we concluded that the optimum values of the electro-optical properties of CNFs on the tip substrate were found at an angle of approximately 50º with a narrow divergence angle. After determining the relationship between the divergence angle and the tip apex angle, the electron emission property was optimized. Analysis of the characteristics of the maximum electron emission state using our computation method indicated that an acute tip covered with CNFs has potential for use as a cathode in electrical devices which require a large FE current with low power consumption. ► There was no report to analyze electrical trajectory of field emission electrons with carbon nanofibers on an acute tip substrate. ► The numerical analysis electro-optically instead of direct purchase of electron beam trajectory was employed in this study. ► The numerical analysis were calculated by an original tool based on surface charge method. ► The possible design of a tip with CNFs to use efficiency a large‐field emission current was proposed.