Vacuum Arc Cathode Spot Characterization on Graphite Materials Using Field Emission Gun Scanning Electron Microscopy (FEGSEM)

1997 ◽  
Vol 3 (S2) ◽  
pp. 1225-1226
Author(s):  
M. Kandah ◽  
J.-L. Meunier ◽  
R. Gauvin
Keyword(s):  
Heat Flux ◽  
Field Emission ◽  
Cathode Spot ◽  
Ion Beam ◽  
Deposition Process ◽  
Vacuum Arc ◽  
Carbon Ions ◽  
Emission Mode ◽  
Current Densities ◽  
Arc Current

Vacuum arcs on graphite cathodes are currently used as sources of carbon ions for the production of diamond-like films in the arc ion-plating (AIP) deposition process. Emission from these cathode sources is concentrated in very localized “cathode spots” having typically 10 (i.m in diameter for graphite cathodes. These spots carry the totality of the arc current, the remaining of the surface being unaffected by the discharge. For electron emission falling in the thermo-field emission mode, extremely high current densities up to 108 -109 Am-2 are induced generating a high localized heat flux to the surface during the spot lifetime. On metallic electrodes, this strong heat flux generates localized surface melting during the microsecond scale spot lifetime. High localized plasma pressures (>10 Atm in the case of copper) were found to exist in the cathode spot volume, leading to the co-emission of micro-droplets of the liquid metal along with the ion beam.

Low Threshold Field Emission From Nanocluster Carbon Films

1999 ◽  
Vol 593 ◽  
Author(s):  
W.I. Milne ◽  
B.S. Satyanarayana ◽  
J. Robertson
Keyword(s):  
Field Emission ◽  
Deposition Process ◽  
Carbon Films ◽  
Vacuum Arc ◽  
Threshold Field ◽  
Bonding Ratio ◽  
Low Threshold ◽  
Current Densities ◽  
Vacuum Arc Deposition ◽  
Arc Deposition

ABSTRACTCarbon films with variable sp3/sp2 bonding ratio can be deposited on a variety of substrates at room temperature, using the cathodic vacuum arc deposition process. The variation in their surface morphology as a function of He and N2partial pressure during growth have been investigated and it has been shown that the morphology of the films can be varied from the mirror like smooth tetrahedrally bonded carbon (ta-C) films through nanocluster to fibrous type carbon. This paper reviews the work carried out on Field Emission from these various carbon films. Threshold fields as low as 1 V/μm for emission current densities of 1 μA/cm2 and emission site densities of up to 104 -105/cm2 have been obtained.

Field Emission from Tetrahedrally Bonded Amorphous Carbon

1997 ◽  
Vol 471 ◽  
Author(s):  
W. I. Milne ◽  
J. Robertson ◽  
B. S. Satyanarayanan ◽  
A. Hart
Keyword(s):  
Field Emission ◽  
Amorphous Carbon ◽  
Applied Field ◽  
Vacuum Arc ◽  
Threshold Field ◽  
Nitrogen Doped ◽  
Bonding Ratio ◽  
Current Densities ◽  
Filtered Cathodic Vacuum Arc ◽  
Tetrahedrally Bonded

ABSTRACTA series of tetrahedrally bonded carbon (ta-C) films have been produced using a Filtered Cathodic Vacuum Arc System. The threshold field and current densities achievable have been investigated as a function of sp3/sp2 bonding ratio and nitrogen content. Typical undoped ta-C films have a threshold field of 15–20V/μm and optimally nitrogen doped films exhibit threshold fields as low as ∼ 5 V/μm. Current densities of typically 10-4 A/cm2 at an applied field of 20V/micron were also obtained.

scholarly journals Evolution of the Cathode Spot Distribution in an Axial Magnetic Field Controlled Vacuum Arc at Long Contact Gap

2017 ◽  
Vol 4 (1) ◽  
pp. 99-103
Author(s):  
B. Tezenas du Montcel ◽  
P. Chapelle ◽  
A. Jardy ◽  
C. Creusot
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Cathode Spot ◽  
Axial Magnetic Field ◽  
Processing Method ◽  
Vacuum Arc ◽  
Single Spot ◽  
High Speed Video ◽  
Video Images ◽  
Arc Current

The distribution of cathode spots in a CuCr25 vacuum arc controlled by an axial magnetic field and ignited on the lateral surface of the cathode is investigated for long gap distances, from the processing of high-speed video images. The processing method includes also estimating the current carried by a single spot and reconstructing the distribution of the current density at the cathode. Various distributions depending partly on the arc current are described.

scholarly journals Correlation of radius of cathode spot of vacuum arc of metals on the size of generated droplets

2021 ◽  
Vol 66 (4) ◽  
pp. 391-398
Author(s):  
G. V. Markov ◽  
A. T. Volochko ◽  
V. G. Zaleski ◽  
N. Yu. Melnik
Keyword(s):  
Experimental Study ◽  
Cathode Spot ◽  
Simple Relation ◽  
Electric Arc ◽  
Vacuum Arc ◽  
Alloy Droplet ◽  
Spot Radius ◽  
Droplet Sizes ◽  
Arc Current ◽  
Pure Metals

The simple relation to estimate the cathode spot radius of a vacuum arc of pure metals is obtained. On its basis, is established between the cathode spot radius and the size of droplets generated by the cathode spot a correlation. This enables to find ways to reduce droplets in the plasma flow, which forms coatings by the vacuum electric arc method. The paper presents the results of experimental study of the droplet sizes depending on the vacuum arc current iд. The size and amount of the droplets on an area of 1 mm2 of the coating surface are determined using the ImageSP program. As the initial data, the microstructures of the coatings are used with an increase of: ç100, ç200, ç500, ç1000, ç1500. The droplets have been generated by a cathode spot of a vacuum arc for the alloy of the composition, at.%: 68Al–8Cr–4Nb–20Si. It is established that the number of droplets with a diameter of < 2 μm is generated most of all, and the number of droplets with a diameter > 10 μm is generated least of all. The number of generated droplets with a diameter from 2 to 10 μm slightly depends on the arc current iд. It is noted that the diameter of the alloy droplet is smaller than the diameter of the droplets generated by the cathode spot on its components due to the fact that the radius of the cathode spot on the alloy is smaller than the radius of the cathode spot on its pure components.

Field Emission Properties of Ion Beam Synthesized SiC/Si Heterostructures by MEVVA Implantation

1998 ◽  
Vol 509 ◽  
Author(s):  
Dihu Chen ◽  
S. P. Wong ◽  
W.Y. Cheung ◽  
E.Z. Luo ◽  
W. Wu ◽  
...  
Keyword(s):  
Field Emission ◽  
Photoelectron Spectroscopy ◽  
Ion Beam ◽  
Metal Vapor ◽  
Ion Source ◽  
Vacuum Arc ◽  
High Dose ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Two Factors

AbstractPlanar SiC/Si heterostructures were formed by high dose carbon implantation using a metal vapor vacuum arc ion source. The variations of the field emission properties with the implant dose and annealing conditions were studied. A remarkably low turn-on field of IV/μm was observed from a sample implanted at 35 keV to a dose of 1.0×1018 cm−2 with subsequent annealing in nitrogen at 1200°C for 2h. The chemical composition depth profiles were determined from x-ray photoelectron spectroscopy and the surface morphology was observed by atomic force microscopy. The formation of a thin surface stoichiometric SiC layer and the formation of densely distributed small protrusions on the surface are believed to be the two factors responsible for the efficient electron field emission.

A Stable Field Emission Electron Source

1977 ◽  
Vol 35 ◽  
pp. 58-59
Author(s):  
W.R. Bottoms ◽  
G.B. Haydon
Keyword(s):  
Field Emission ◽  
Signal To Noise Ratio ◽  
High Brightness ◽  
Electron Sources ◽  
Brightness Field ◽  
Current Densities ◽  
Properties Of Materials ◽  
Stable Field ◽  
Stable Current ◽  
Careful Design

There is great interest in improving the brightness of electron sources and therefore the ability of electron optical instrumentation to probe the properties of materials. Extensive work by Dr. Crew and others has provided extremely high brightness sources for certain kinds of analytical problems but which pose serious difficulties in other problems. These sources cannot survive in conventional system vacuums. If one wishes to gather information from the other signal channels activated by electron beam bombardment it is necessary to provide sufficient current to allow an acceptable signal-to-noise ratio. It is possible through careful design to provide a high brightness field emission source which has the capability of providing high currents as well as high current densities to a specimen. In this paper we describe an electrode to provide long-lived stable current in field emission sources.The source geometry was based upon the results of extensive computer modeling. The design attempted to maximize the total current available at a specimen.

Preparation and characterization of thin films of carbon nitride

1995 ◽  
Vol 53 ◽  
pp. 104-105
Author(s):  
L. Wan ◽  
R. F. Egerton
Keyword(s):  
Carbon Nitride ◽  
Arc Discharge ◽  
Ion Beam ◽  
Chemical Vapor ◽  
Reactive Sputtering ◽  
Vacuum Arc ◽  
Specimen Preparation ◽  
Bonding Structure ◽  
Electron Energy Loss

INTRODUCTION Recently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4 are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNX films deposited by two different methods.SPECIMEN PREPARATION Specimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.

The cathode spot of a vacuum arc

1978 ◽  
Vol 125 (8) ◽  
pp. 665-706 ◽  
Author(s):  
G.A. Lyubimov ◽  
V.I. Rakhovskii
Keyword(s):  
Cathode Spot ◽  
Vacuum Arc

Energy Balance on Current Density Distribution of Cathode Spot in Vacuum Arc

2019 ◽  
Vol 139 (5) ◽  
pp. 302-308 ◽  
Author(s):  
Shinji Yamamoto ◽  
Soshi Iwata ◽  
Toru Iwao ◽  
Yoshiyasu Ehara
Keyword(s):  
Energy Balance ◽  
Density Distribution ◽  
Current Density ◽  
Cathode Spot ◽  
Current Density Distribution ◽  
Vacuum Arc
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