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Field electron emission from carbon nanofibers (CNFs) grown on a tungsten tip has been characterized by measuring emission current-voltage (I-V) curves and observing emission patterns on a phosphor screen. CNFs were vertically grown on the tip by plasma-enhanced chemical vapor deposition. Field emission from the CNFs over 100 μA was strongly dependent on emitter-anode distance, and the dominant field electrons were emitted within an angular spread of Δθ∼25°, indicating the electron emission took place mainly from the emitter’s apex area. By analyzing the I-V curves with the aid of the Fowler–Nordheim theory, the maximum current density was estimated to be about J=2×109 A/m2. [ABSTRACT FROM AUTHOR]

Field emitters comprised of aligned carbon nanotubes are shown to be promising as a primary electron source in an x-ray tube working in a nonultrahigh vacuum ambience. At a pressure of 2x10[sup -7] Torr, the nanotube emitters continue to emit electrons for more than 1 h, and yield better resolved x-ray images than do thermionic emitters, independently of whether the sample is biological or nonbiological. The near-uniformity in energy distribution of electrons emitted from carbon nanotubes might be related to the improved image quality in the field-emission mode. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Field emission transmission electron microscopy has revealed the presence of atomic filaments extending from the open edge of a graphite cage formed in a glow-discharge plasma. The filaments are vapor grown, presenting complicated deformations such as curling, waving, and looping in the free space. The filaments correspond well to one carbon atom in diameter, strongly indicating that they are linear chains of carbon atoms, the presence of which was earlier suggested by Smalley et al. [Science 269, 1550 (1995)]. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]