Electron Emission from Pentagons on a Carbon Nanotube Tip Revealed by Field Emission Microscopy

AbstractField emission of electrons from multiwall carbon nanotubes (MWCNTs) has been investigated by field emission microscopy (FEM) in an ultra-high vacuum chamber. An MWCNT whose tip is capped by curved graphite layers gives a FEM pattern consisting of 6 bright pentagons when the surface of the nanotube tip is clean. Even in the ultra-high vacuum with a base pressure of about 10-10 Torr, residual gas molecules, attracted by polarization forces, adsorb on the nanotube tips. The adsorbed molecules reside preferentially on the pentagonal sites, giving bright spots in the FEM pattern. A flash heating the emitter at about 1300 K allows the molecules to desorb, and the nanotube emitter recovers the original clean surfaces. The adsorption and desorption of gas molecules are responsible for stepwise increases and decreases in the emission current, respectively.

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Field Emission Properties of Polymer Graphite Tips Prepared by Membrane Electrochemical Etching

Nanomaterials ◽

10.3390/nano10071294 ◽

2020 ◽

Vol 10 (7) ◽

pp. 1294

Author(s):

Alexandr Knápek ◽

Rashid Dallaev ◽

Daniel Burda ◽

Dinara Sobola ◽

Mohammad M. Allaham ◽

...

Keyword(s):

Field Emission ◽

Electrochemical Etching ◽

High Vacuum ◽

Ultra High Vacuum ◽

Test Field ◽

Current Voltage ◽

Field Emission Microscopy ◽

Emission Behavior ◽

Current Voltage Characteristics ◽

Emission Microscopy

This paper investigates field emission behavior from the surface of a tip that was prepared from polymer graphite nanocomposites subjected to electrochemical etching. The essence of the tip preparation is to create a membrane of etchant over an electrode metal ring. The graphite rod acts here as an anode and immerses into the membrane filled with alkali etchant. After the etching process, the tip is cleaned and analyzed by Raman spectroscopy, investigating the chemical composition of the tip. The topography information is obtained using the Scanning Electron Microscopy and by Field Emission Microscopy. The evaluation and characterization of field emission behavior is performed at ultra-high vacuum conditions using the Field Emission Microscopy where both the field electron emission pattern projected on the screen and current–voltage characteristics are recorded. The latter is an essential tool that is used both for the imaging of the tip surfaces by electrons that are emitted toward the screen, as well as a tool for measuring current–voltage characteristics that are the input to test field emission orthodoxy.

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Field emission microscopy of adsorption and desorption of residual gas molecules on a carbon nanotube tip

Surface Science ◽

10.1016/s0039-6028(01)01338-3 ◽

2001 ◽

Vol 490 (3) ◽

pp. 296-300 ◽

Cited By ~ 61

Author(s):

Koichi Hata ◽

Akihiro Takakura ◽

Yahachi Saito

Keyword(s):

Carbon Nanotube ◽

Field Emission ◽

Adsorption And Desorption ◽

Field Emission Microscopy ◽

Gas Molecules ◽

Residual Gas ◽

Emission Microscopy

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A Field Emission System For Transmission Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071934 ◽

1973 ◽

Vol 31 ◽

pp. 298-299

Author(s):

Michel Troyonal ◽

Huei Pei Kuoal ◽

Benjamin M. Siegelal

Keyword(s):

Electron Microscope ◽

Field Emission ◽

Optical System ◽

High Vacuum ◽

Ultra High Vacuum ◽

Objective Lens ◽

Electron Optical System ◽

Cross Sectional ◽

Transmission Electron ◽

Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

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