Electron emission properties of graphene-oxide-semiconductor planar-type electron emission devices

Abstract

Local current-voltage estimation and characteristization based on field emission image processing of large-area field emitters

Mechanism of Highly Efficient Electron Emission from a Graphene/Oxide/Semiconductor Structure

“…This is because of the voltage drop caused by the relatively high sheet resistance of the graphene gate electrode. Although we confirmed that electron emission occurs over the whole emission area by observing the electron emission pattern at a phosphor screen in a previous study, 20 for the case of a large emission area, the electron emission current at the center of the emission area would be smaller than that at the device edge because of the voltage drop at the center of the gate electrode. This would affect the uniformity of the electron emission of the GOS devices.…”

“…In addition, we observed that the electron emission efficiency of the GOS devices fabricated by Ga vapor-assisted CVD showed no dependence on the graphene electrode thickness for thicknesses ranging from 1.8 to 7 nm and was below 1% in our previous study. 20 Therefore, the emission efficiency difference cannot be fully explained by the thickness difference of the graphene electrode. Another possible explanation is the defects of the oxide layer causing the hopping conduction of the electrons.…”

“…In our previous studies focusing on the high electron transmittance of a graphene plane, we developed highly efficient planar-type electron emission devices based on a graphene/oxide/semiconductor (GOS) structure that utilized graphene as electron transparent electrodes. − These devices utilize the following features of graphene: it is a very thin conductive material at the atomic level and has a small electron inelastic scattering cross section. There was, thus, no need for the high carrier mobility of graphene in this device.…”

“…In fact, the electron emission efficiency and electron emission current density of planar-type electron emission devices using a low crystal quality polycrystalline multilayer graphene gate electrode directly synthesized on the oxide layer were more than 4 orders of magnitude greater than those of conventional metal/oxide/semiconductor (MOS)-type devices. − This drastic improvement of the device performance was achieved by the suppression of the electron inelastic scattering within the top-gate electrode resulting from the use of graphene instead of a metal. The detailed operation principles of the planar-type electron emission devices are described in previous reports. ,, Several applications of these devices such as in electron microscopes and as the neutralizer for the ion thruster of small satellites are currently in progress in our group. Another possible application of GOS structures is electrochemical devices that use hot electrons for the hydrogen evolution reaction in an acidic solution because MOS-type electron emission devices including GOS devices can operate in a liquid .…”

High-performance planar-type electron source based on a graphene-oxide-semiconductor structure

“…These excellent features of graphene suggest the ideal material for the gate electrode of the MOS type electron emission source. In fact, the efficiency of planar-type electron sources has been improved to 0.3~13 % by suppression of electron scattering using graphene gate electrode [27][28][29][30][31][32]. However, further improvement of the electron emission efficiency of the planar-type electron emission source has been required to obtain sufficient electron beam current from an emission area equivalent to the electron source sizes of the conventional electron guns.…”