Polymerization by high electric fields: Field emission and field ionization

An atom probe field ion microscope (APFIM) has been constructed inside a NORAN Instruments Automated Digital Electron Microscope (ADEM). The ADEM is a scanning electron microscope (SEM) with a field emission source and a very large vacuum chamber. The APFIM has positive and negative high voltage capability and uses a microchannel-plate/phosphor screen assembly as an imaging and single-ion detector. The APFIM specimen can be cooled by a cryogenic refrigerator. The motivation for this study was the need to deliver an electron beam to the apex of an APFIM specimen while a high field is applied. The beam will be used to thermally pulse the field evaporation rate. The expected field-induced image shift and distortion has been studied previously in a transmission EM with a liquid metal field emission source as a specimen.Fig. 1 shows the interior of the instrument. Computer simulations were done for electron trajectories with negative and positive voltages applied to the emitter based on a simple paraboloidal electric field model described previously.

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Studies of field emission process influence on changes in CNT films with different CNT superficial density

Materials Science-Poland ◽

10.1515/msp-2018-0001 ◽

2018 ◽

Vol 36 (1) ◽

pp. 27-33

Author(s):

Izabela Stępińska ◽

Elżbieta Czerwosz ◽

Mirosław Kozłowski ◽

Halina Wronka ◽

Piotr Dłużewski

Keyword(s):

Field Emission ◽

Electric Fields ◽

Vapor Deposition ◽

Physical Vapor Deposition ◽

Chemical Vapor ◽

Destructive Effect ◽

Electric Power Supply ◽

Cold Cathodes ◽

High Electric Fields ◽

The Impact

Abstract Field emission from materials at high electric fields can be associated with unfavorable or even destructive effect on the surface of the investigated cathode. The impact of high voltage electric power supply causes locally very strong electric fields focusing on the cathode surface. It causes a number of phenomena, which can adversely affect the morphology and the structure of the cathode material. Such a phenomenon is, for example, peeling of an emissive layer from the substrate or its burnout. It results in tearing of the layer and a decrease or loss of its ability to electrons emission. The cold cathodes in a form of CNT films with various CNTs superficial distribution are obtained by physical vapor deposition followed by chemical vapor deposition. CNTs are catalyzed in pyrolytic process with xylene (CVD), by Ni in a form of nanograins (few nm in size) placed in carbonaceous matrix. These films are built of emissive CNTs - carbonaceous film deposited on different substrates. In this work, the morphology and topography of superficial changes resulting from external electric field in such films were investigated.

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Nanodiamond Coating for Field Emission Filaments

Materials ◽

10.1115/imece2003-43327 ◽

2003 ◽

Author(s):

A. V. Kvit ◽

V. V. Zhirnov ◽

T. Tyler ◽

J. J. Hren

Keyword(s):

Field Emission ◽

Electric Fields ◽

Diamond Particle ◽

Aging Effect ◽

Emission Properties ◽

Coated Metal ◽

Conductive Surface ◽

Surface Localization ◽

High Electric Fields ◽

Z Contrast

Nanodiamond is very important for autoemission applications because it allows investigators to reduce electric field for electron emission current generation. Moreover, we can also consider nanodiamonds as “bricks” for new method of diamond coating growth. In this paper we describe the formation and investigation of nanodiamond-based coating on Mo needles. Manipulation of nanodiamond particles with high electric fields allows us to prepare systems of isolated diamond quantum dots on a conductive surface. Localization of an isolated single-crystalline diamond particle ∼5 nm in size on the «tip of a needle» presents an unique opportunity for studies of correlations between the structural and emission properties of individual diamond nanoparticles. Combinations of TEM observations, field emission measurements, and repeated diamond depositions on the same emitter provided a direct comparison of the effects of various amounts of nanodiamond particles on the emission properties of a coated metal field emitter. By utilizing Z-contrast and EELS technique we investigated distribution of nitrogen impurity inside individual nanoparticle and aging effect (increasing of s p2 fraction on the surface of nanodiamond with time).

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Atomic Spectroscopy in the FIM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100145157 ◽

1986 ◽

Vol 44 ◽

pp. 758-761

Author(s):

J. J. Hren ◽

S. D. Walck

Keyword(s):

Electron Microscope ◽

Electric Fields ◽

Atom Probe ◽

Atomic Spectroscopy ◽

Single Atom ◽

Statistical Sampling ◽

Commercial Instrument ◽

Available Technology ◽

High Electric Fields ◽

Field Ion Microscope

The field ion microscope (FIM) has had the ability to routinely image the surface atoms of metals since Mueller perfected it in 1956. Since 1967, the TOF Atom Probe has had single atom sensitivity in conjunction with the FIM. “Why then hasn't the FIM enjoyed the success of the electron microscope?” The answer is closely related to the evolution of FIM/Atom Probe techniques and the available technology. This paper will review this evolution from Mueller's early discoveries, to the development of a viable commercial instrument. It will touch upon some important contributions of individuals and groups, but will not attempt to be all inclusive. Variations in instrumentation that define the class of problems for which the FIM/AP is uniquely suited and those for which it is not will be described. The influence of high electric fields inherent to the technique on the specimens studied will also be discussed. The specimen geometry as it relates to preparation, statistical sampling and compatibility with the TEM will be examined.

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