Dynamics and Interaction of Active Centers at Nanocarbon Electron Emitters

Архипов, А. В.; Mishin, M. V.; Sominskii, G. G.; Kriegel, B.A.; Parygin, I.V.; Uvarov, A. A.

doi:10.1109/ivnc.2006.335438

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…This phenomenon can be explained by the dynamic properties of field emission from such materials (including emission efficiency boosting in a rapidly decreasing electric field) investigated in our previous works. 8,9 …”

Section: Experiments With the Gauge Prototypementioning

confidence: 99%

Carbon‐film field‐emission cathodes in a compact orbitron‐type ionization vacuum sensor

Alexandrov

Архипов

Mishin

et al. 2007

Surface & Interface Analysis

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A possibility to using large-area field-emission cathodes as electron sources in ionic vacuum sensors was investigated. In the specially developed electron-optic scheme, electrons are extracted from a box-shaped cathode by the field of two anode strings. For a large part of the cathode, trajectories of emitted electrons are infinite (in theory), thus high efficiency of gas ionization and overall gauge sensitivity can be achieved. Experimental testing of a sensor prototype has demonstrated general viability of the proposed principle. For a residual gas pressure of about 10 −5 Torr and a cathode emission current 10 µA, the current of collected ions had value of about 1 nA. PROJECT BACKGROUND AND OBJECTIVEThe principle of operation of the most popular highvacuum sensors involves the measurement of ionic current originating from interaction of residual gas with a flow of electrons. Subclasses of ionic vacuum gauges 1 differ in the type of electron source used. Traditionally, the choice was between thermionic cathodes and forms of self-maintained discharge (magnetron, Penning, etc.). Rapid progress in technologies of nanostructured carbon materials 2 -4 suggests new promising solutions for these devices. Carbon-film distributed-field electron emitters combine advantageous features, such as low energy consumption, durability to poor vacuum, zero start-up time, simple design, small weight and no need for magnets. These features potentially make them more competitive in comparison with thermionic and discharge electron sources. The principal objective of the work reported here was the development and testing of ion vacuum sensor designs adapted for operation with carbonfilm field-emitters, in such a way as to realize their inherent advantages. GAUGE ELECTRON-OPTICAL SYSTEM DESIGNThe electron-optical system (EOS) of the developed vacuum sensor (Fig. 1) and their acceleration, emission current control and electron flow confinement and direction of the generated ions to the collector. The anode consists of two thin (50-100 µm) tungsten wires fixed through spring holders to ceramic insulators. The cathode has a 6 ð 6 mm cross-section and a length of 50 mm, and consists of two components: the foil emitter with an active carbon layer and the mesh electrode separating the diode from the ion collector volume. For these dimensions, the macroscopic electric field strength needed at the cathode for field electron emission (E D 0.3-3 V/µm) is achieved for applied voltages U D 1-10 kV.Electrode shapes and positions were optimized by digital simulation of the electron motion to achieve maximum trajectory length for particles emitted from different parts of the cathode. As shown in Fig. 2, for approximately 20% of the cathode area in the optimized EOS configuration, the particles are emitted into a 2D trap and can leave the system only in the axial direction under the influence of the comparatively weak axial electric field component. This enables efficient utilization of the electron energy for the purpose of ionizing residual gas m...

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Section: Experiments With the Gauge Prototypementioning

confidence: 99%

Carbon‐film field‐emission cathodes in a compact orbitron‐type ionization vacuum sensor

Alexandrov

Архипов

Mishin

et al. 2007

Surface & Interface Analysis

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“…In our previous work [1,2], we observed complicated behavior of field-induced electron emission from nanocarbon films in non-stationary (pulsed) electric field, including strong temporal dispersion with characteristic times as large as about 10 ts. At the investigated materials, the emission current is produced at numerous low-aspect-ratio active centers.…”

mentioning

confidence: 94%

Time- and Area-Resolved Investigation of Field-Induced Electron Emission from Nanocarbon Films

Архипов

Mishin

Sominskii

et al. 2006

2006 19th International Vacuum Nanoelectronics Conference

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In our previous work [1,2], we observed complicated behavior of field-induced electron emission from nanocarbon films in non-stationary (pulsed) electric field, including strong temporal dispersion with characteristic times as large as about 10 ts. At the investigated materials, the emission current is produced at numerous low-aspect-ratio active centers. These centers can be expected to interact -for instance, via currentinduced voltage drop at nanocarbon grains. Thus, the emitter surface represents a kind of 2d medium with spatial and temporal dispersion, principally suitable for development of oscillations and waves. Detection and characterization of these oscillatory phenomena can give new information on properties, performance and interaction of efficient emission centers.To investigate fluctuations of emission pattern with area resolution, we use the apparatus schematically showed in Fig. 1. Anode 4 and cathode guard electrode 3 form 2.5 mm-wide quasi-planar field gap in a vacuum chamber pumped typically to 10-7 Torr. The studied emitting structure 2 is placed behind an orifice in the guard electrode. Heater 1 serves for conditioning of the sample prior to its investigation. Electrons extracted from the sample pass through a 2 mm-diameter diaphragm in the anode to strike the phosphor screen 5 deposited at a polished end of light-guide bunch 6. Emission images can be observed at the other end of the bunch, outside of the vacuum chamber. To measure a signal representing emission current density at a selected spatial position, the light flux from the corresponding image spot is collected with an optic fiber probe 7 and then directed to a photomultiplier 8. The present system includes four such data channels. Usually, four probes are arranged in quadratic or linear array with 100-150 pm period, and whole array is scanned across the image to obtain measurable signal magnitudes at all data inputs.Time resolution of the technique is limited by the phosphor afterglow at approximately 0.1 zIs level, while its spatial resolution is determined by 50 gm probe fiber diameter. Probe signals are measured in the form of 4096-points waveforms with time step between 50 ns and 1.6 gs, which allows to cover the frequency band 4 5 () L 72 )~~~~~~~~D igital \) Figure 1. Schematic diagram of the experimental setup. See details in text.

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Dynamics and Interaction of Active Centers at Nanocarbon Electron Emitters

Cited by 2 publications

References 2 publications

Carbon‐film field‐emission cathodes in a compact orbitron‐type ionization vacuum sensor

Carbon‐film field‐emission cathodes in a compact orbitron‐type ionization vacuum sensor

Time- and Area-Resolved Investigation of Field-Induced Electron Emission from Nanocarbon Films

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