Building a backlight unit with lateral gate structure based on carbon nanotube field emitters

Coplanar-gate ZnO nanowire field emitter arrays with enhanced gate-control performance using a ring-shaped cathode

Nanowire field emitters have great potential for use as large-area gated field emitter arrays (FEAs). However, the micrometer-scale cathode patterns in gated FEA devices will reduce regulation of the gate voltage and limit the field emission currents of these devices as a result of field-screening effect among the neighboring nanowires. In this article, a ring-shaped ZnO nanowire pad is proposed to overcome this problem. Diode measurements show that the prepared ring-shaped ZnO nanowire pad arrays shows uniform emission with a turn-on field of 5.9 V/µm and a field emission current density of 4.6 mA/cm² under an applied field of 9 V/µm. The ZnO nanowire pad arrays were integrated into coplanar-gate FEAs and enhanced gate-controlled device characteristics were obtained. The gate-controlled capability was studied via microscopic in-situ measurements of the field emission from the ZnO nanowires in the coplanar-gate FEAs. Based on the results of both simulations and experiments, we attributed the enhanced gate-controlled device capabilities to more efficient emission of electrons from the ZnO nanowires as a result of the increase edge area by designing ring-shaped ZnO nanowire pad. The results are important to the realization of large-area gate-controlled FEAs based on nanowire emitters for use in vacuum electronic devices.

Empirical expression for the emission site density of nanotube film emitters

The influence of surface roughness on emission site density (ESD) is investigated for nanotube film emitters. An empirical expression for film emitters, [Formula: see text], where B is the intercept in the modified Fowler-Nordheim (FN) plots, A(CNT) the emission area of one site, and C related to the work function, is derived from the FN theory and experimentally proved. This expression effectively excludes the influence of electric field strength, being different from the conventional method of counting site numbers from emission patterns. By using this equation and emission patterns, variation in ESD, induced by the change in cathode-anode distance, is confirmed for film emitters with rough surfaces. This variation is ascribed to the change in screen-effect strength among emission sites. It is also found that the smaller gaps produce the higher emission uniformity and site densities for rough-surface film emitters.