The electron distribution of open-ended single-walled carbon nanotubes (CNTs) with chirality indexes (7,0) and (5,5) in field emission conditions was calculated via a multi-scaled algorithm. The field emission images were produced numerically. It was found that the emission patterns change with the applied macroscopic field. Especially, the symmetry of the emission pattern of the (7,0) carbon nanotube is breaking in the lower field but the breaking is less obvious in the higher field. The magnification factor increases with the applied macroscopic field.

Weiliang Wang;宁生 许;Zhibing Li

Ultramicroscopy

2009-9

The field electron emission current from graphene is calculated analytically on a semiclassical model. The unique electronic energy band structure of graphene and the field penetration in the edge from which electrons emit have been taken into account. The relation between the effective vacuum barrier height and the applied field is obtained. The calculated slope of the Fowler-Nordheim plot of the current-field characteristic is in agreement with existing experiments.

Weiliang Wang;Xizhou Qin;宁生 许;Zhibing Li

Journal of Applied Physics

2011-2-15

A general approach to the coherent field electron emission of nanoemitters is proposed and applied to graphene. We will show that the coherence of the Dirac quasiparticles of graphene can be transmitted into the vacuum via electric-field-assisted electron emission at temperatures up to 1000 K. A dragonfly emission pattern with a dark body and two pairs of wings is predicted for the armchair edge as evidence of the pseudospin mixing and the odd parity of the π orbitals. Thus the phase information of the quantum states of the nanoemitters is revealed by the emission image. Moreover, this phenomenon leads to a novel coherent electron line source that can produce interference patterns of extended objects with linear sizes comparable to the length of the graphene edge. The angular distribution of the emission and the total emission current will be given analytically.

Zhibing Li;宁生 许;H. J. Kreuzer

Physical Review B - Condensed Matter and Materials Physics

2012-3-21

Analytical solutions of the edge states were obtained for the (N, 0) type carbon nanotubes with distorted ending bonds. For N = 5 and N ≥ 7, it was found that the symmetric edge states are mixed via the distortion to form asymmetric edge eigenstates. The density of the π electrons in the last carbon layer exhibits axial rotation symmetry breaking explicitly. The distortion modes depend on the occupation of the edge states, implying that the symmetry of the electron density at the apex could be changed discontinuously by the external electronic field.

Weiliang Wang;Yu Xia;宁生 许;Zhibing Li

Journal of Physical Chemistry C

2009

Field emission (FE) is based on the physical phenomenon of quantum tunneling, in which electrons are injected from the surface of materials into vacuum under the influence of an applied electric field. A variety of field emission cold cathode materials have been developed to date. In this review, we shall focus on several kinds of novel cold cathode materials that have been developed in the past decade. These include materials for microfabricated field-emitter arrays, diamond and related films, carbon nanotubes, other quasi one-dimensional nanomaterials and printable composite materials. In addition, cold cathode materials have a wide range of applications such as in flat panel displays, high-power vacuum electronic devices, microwave-generation devices, vacuum microelectronic devices and vacuum nanoelectronic devices. Applications are in consumer goods, military industries and also space technology. A comprehensive overview of the various applications is presented. Recently, recognizing the strong possibility that vacuum nanoelectronic devices using quasi one-dimensional nanomaterials, such as carbon nanotubes may emit electrons with driving voltages comparable to that of a solid-state device, there is a growing interest in novel applications of such devices. With such exciting opportunities, there is now a flurry of activities to explore applications far beyond those considered for the conventional hot cathodes that operate on thermionic emission. We shall discuss the details of a number of fascinating potential applications.

宁生 许;S. Ejaz Huq

Materials Science and Engineering: R: Reports

2005-1-31

A thermodynamic mechanism has been developed to explain the formation of aligned cupric oxide (CuO) nanowires synthesized by thermal oxidation of copper substrates at different conditions. The 1D morphology and temperature dependence of parameters of nanowires were explained.

Yingxin Luo;宁生 许

2010

Graphene has a one-dimensional edge of atomic thickness, excellent electrical conductivity, and good mechanical properties, which qualify it as an attractive novel field emission emitter. Several groups had demonstrated that graphene does show promising electron emission properties, such as low emission threshold field and large emission current density[1-7].

Weiliang Wang;Xizhou Qin;宁生 许;Zhibing Li

2010

SiN_x thin films were prepared by RF plasma enhanced chemical vapor deposition. Composition, structure, surface morphology and optical properties of the films were analyzed by X-ray fluorescence, IR transmittance, IR reflectance and SEM. The analysis shows that the main composition of the films is SiN_0.35. The nitrogen atom takes part in reaction with the silicon atom and Si-N bond is formed, while there are also some Si-H and N-H bonds in the films. The films have very low IR reflectance across the full 8-13 μm bond and high reflectance elsewhere. Then the growth mechanism of the films was explained by SEM observation.

Zongcun Liang;Hui Shen;Jianhong Li;宁生 许

Taiyangneng Xuebao/Acta Energiae Solaris Sinica

2001-7

An experimental study has been carried out into the optical activities associated with surface flash-over on high-voltage insulators in vacuum, aimed at determining the physical origin of the flash-over process. This involves using a 'transparent anode' to form, with combinations of cathode-insulator regimes, a number of electrode configurations, in order to observe the field electron emission and the optical events occurring during surface flash-over. In particular, the flash-over characteristics of two types of insulator shapes, cylindrical insulators and truncated cone insulators, were investigated. The latter allow spatially resolved imaging of the optical activities at two triple junctions and the surface of the insulators. Using this imaging technique in conjunction with the real-time recording function of a video camera system, four types of optical images have been identified. In addition, the influences of temperature and helium conditioning upon the characteristics of a flash-over were studied. Finally, a new model has been proposed to account for these experimental findings, which assumes accumulation of charges at two interface regions at two triple junctions, and that subsequent initiation of flash-over results from the breakdown of interface layers.

R. V. Latham;A. Abbot;I. D. Chalmers;宁生 许

Journal Physics D: Applied Physics

1994-2-14

Jinglei Ping;Zhibing Li;宁生 许

2006