Influence of nanoscale geometry on the thermodynamics of electron field emission

Fisher, Timothy S.

doi:10.1063/1.1421418

Cited by 25 publications

(12 citation statements)

References 17 publications

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“…The model was described in a recent paper 13 and is summarized here for clarity. The model was described in a recent paper 13 and is summarized here for clarity.…”

Section: ͑1͒mentioning

confidence: 99%

High-temperature electron emission from diamond films

Shin

Fisher

Walker

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Articles you may be interested inSubstrate-diamond interface considerations for enhanced thermionic electron emission from nitrogen doped diamond films Field emission characteristics of boron nitride films deposited on Si substrates with cubic boron nitride crystal grains J.This work examines electron field-emission characteristics of polycrystalline diamond films at elevated temperatures. Diamond is an excellent material as a field emitter because of its exceptional mechanical hardness and chemical inertness. The motivation behind this study involves the use of field emitters in applications where high temperatures exist. Nitrogen-doped polycrystalline diamond films were grown by plasma-enhanced chemical-vapor deposition. To investigate the effect of increased temperatures on field emission, current-voltage measurements were taken from the same diamond film at varying temperatures. Results from these measurements indicate a decrease in the turn-on voltage with increasing temperature. Further analysis of the temperature dependence of emission is achieved through parameter estimation of the effective emitting area, field enhancement factor, and work function. These results suggest that thermally excited electrons are responsible for improved emission at high temperature.

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“…The model was described in a recent paper 13 and is summarized here for clarity. The model was described in a recent paper 13 and is summarized here for clarity.…”

Section: ͑1͒mentioning

confidence: 99%

High-temperature electron emission from diamond films

Shin

Fisher

Walker

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…Research in the field of electron emission often focuses on reducing the energy barrier in a material that an electron must overcome for emission, also referred to as the work function. More recent research with carbon materials has investigated the fabrication of nanostructures that can confine electrons, forcing them to higher energy levels, thereby increasing emission intensity (Huang et al, 1995;Fisher, 2001;Tavkhelidze et al, 2006). For example, Obraztsov has performed extensive research in both classical and non-classical field emission of nanostructured carbon materials demonstrating reduced turn-on voltages of field emission and reduced work functions relative to carbon structures with macro or micro scale features (Obraztsov et al, 2000(Obraztsov et al, , 2002(Obraztsov et al, , 2003.…”

Section: Introductionmentioning

confidence: 99%

Work Function Characterization of Potassium-Intercalated, Boron Nitride Doped Graphitic Petals

et al. 2017

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This paper reports on characterization techniques for electron emission from potassiumintercalated boron nitride-modified graphitic petals (GPs). Carbon-based materials offer potentially good performance in electron emission applications owing to high thermal stability and a wide range of nanostructures that increase emission current via field enhancement. Furthermore, potassium adsorption and intercalation of carbon-based nanoscale emitters decreases work functions from approximately 4.6 eV to as low as 2.0 eV. In this study, boron nitride modifications of GPs were performed. Hexagonal boron nitride is a planar structure akin to graphene and has demonstrated useful chemical and electrical properties when embedded in graphitic layers. Photoemission induced by simulated solar excitation was employed to characterize the emitter electron energy distributions, and changes in the electron emission characteristics with respect to temperature identified annealing temperature limits. After several heating cycles, a single stable emission peak with work function of 2.8 eV was present for the intercalated GP sample up to 1,000 K. Up to 600 K, the potassium-intercalated boron nitride modified sample exhibited improved retention of potassium in the form of multiple emission peaks (1.8, 2.5, and 3.3 eV) resulting in a large net electron emission relative to the unmodified graphitic sample. However, upon further heating to 1,000 K, the unmodified GP sample demonstrated better stability and higher emission current than the boron nitride modified sample. Both samples deintercalated above 1,000 K.

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“…For W < U 0 , the transmission decays exponentially as W decreases, while resonant effects are clearly observable for W > U 0 . The same problem has also been solved using the NEGF simulation as outlined in Eq's (16) through (20) using 200 equally spaced lattice points, and the result is also shown in Fig. 3, where it is seen that the NEGF results are in excellent agreement with the exact solution.…”

Section: Rectangular Barriermentioning

confidence: 62%

“…The effect of tip geometry on electron emission has also been explored, revealing that the local electric fields at small tips substantially increases emission current [14]. In addition to the current increase they provide, sharp emission tips also favor the emission of high-energy electrons, making them attractive for cooling applications [15,16]. Recently, additional cooling benefit has been shown to exist for very narrow emission gaps that lower the height of the potential barrier and reduce undesirable space-charge effects in the vacuum region [17].…”

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Analysis and simulation of refrigeration by electron emission

Westover

Fisher

Thermal and Thermomechanical Proceedings 10th Intersociety Conference on Phenomena in Electronics Systems, 2006. ITHERM 2006.

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Phenomena based on nanoscale transport processes offer new possibilities for direct refrigeration by electron emission at room temperature. Electron emission is the process by which electrons escape from the surface of a conductor either by overcoming the potential barrier at the surface or by tunnelling through it. Because the average emitted electron energy may be higher or lower than the energy of the replacement electrons, a heating or cooling effect, known as the Nottingham effect, can occur at the emitter. Theoretical studies indicate the possibility of very large ( > 100 W/cm 2 ) cooling rates for low work function emitters; however, nanometer range emission gaps are necessary to produce a device with a sufficiently high coefficient of performance to be useful in most practical cooling applications. In this regime of low work function and narrow emission gap, the traditional approach involving the WKB approximation to solve for electron transmission across the gap breaks down. In this study, a non-equilibrium Green's function (NEGF) method is employed to model the energy exchange attending field emission for a range of emitter work functions and vacuum gap distances. Predictions indicate that a cooling density of approximately 100 W/cm 2 is possible for a 0.7 eV work function device emitting across a vacuum gap of approximately 5 nm. Operating under those conditions the cooling mechanism would require an emission current density of approximately 350 A/cm 2 and could have a coefficient of performance as high as 0.6.

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Influence of nanoscale geometry on the thermodynamics of electron field emission

Cited by 25 publications

References 17 publications

High-temperature electron emission from diamond films

High-temperature electron emission from diamond films

Work Function Characterization of Potassium-Intercalated, Boron Nitride Doped Graphitic Petals

Analysis and simulation of refrigeration by electron emission

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