<i>Ab initio</i>
 calculation of field emission from metal surfaces with atomic-scale defects

Toijala, Heikki; Eimre, Kristjan; Kyritsakis, Andreas; Zadin, Vahur; Djurabekova, Flyura

doi:10.1103/physrevb.100.165421

Cited by 15 publications

(7 citation statements)

References 74 publications

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“…Notice the variation found in the local work function, field emission factor, and the emission area with the voltage range. These deductions are consistent with the finding of Toijala et al [30], who used density functional theory (DFT) and quantum transport calculations to demonstrate the effect of an atomic-level surface imperfection on the bulk work function of copper (4.76 eV). Accordingly, the lowering of the work function occurs locally by 0.32 eV with an adatom and 0.51 eV with a pyramid defect present at the (111) surface, leading thereby to a significant increase in the field emission current.…”

Section: Emission Characteristicssupporting

confidence: 90%

“…Accordingly, the operational parameters like work function, field enhancement factor, and the effective emission area vary with the bias. Toijala et al [30] emphasized the importance of atomic-level defects at the emitter tip and observed reduction of the work function (e.g., from the bulk value of 4.76 eV by 0.32 or 0.51 eV in copper). Interpretation of I-V data poses significant challenges in case of 1D nanowires, as many emission parameters extracted and reported in the literature are physically unrealistic.…”

Section: Introductionmentioning

confidence: 99%

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On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes

Singh,

Kumar

2023

Nano Ex.

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The self-assembled V2O5 and TiO2 nanowires are prepared hydrothermally from vanadium (V) hydroxylamido complex and titanium oxide powder, respectively, and studied for their crystalline phase, morphology, and electron emission characteristics. V2O5 is shown to exhibit an orthorhombic phase with preferential growth of the (010) face along the [010] direction, diameter 100-400 nm, and length several micrometers. TiO2 nanowires depict a monoclinic β-phase with a typical diameter of ~ 30 nm. Their bundles serve as potential cathodes giving electron emission following the Fowler-Nordheim (F-N) mechanism but from infinitely small areas with large field enhancement factors. In comparison, β-TiO2 provides better emission characteristics at similar operating parameters (e.g., low threshold voltage 250-400 V and current density 109-1013 A/m2). The unique properties (viz., tip geometry, roughness, and local field enhancement) of one-dimension (1D) nanowires make them prospective candidates for high-brightness electron sources and development of the display devices [1-7]. A simple procedure developed by the authors is applied successfully in actual evaluation of the field emission parameters from the current-voltage data. This involves F-N formulation with physical considerations like variation of work function, effective emission area, and field enhancement factor [32].

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Section: Emission Characteristicssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes

Singh,

Kumar

2023

Nano Ex.

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“…al., on copper (100) surface have shown a significant effect on the work function due to microstructures [46]. An ab initio computational method has been developed to calculate the field-emitted current from defective metal surfaces by combining the density functional theory and electronic structure calculations with quantum transport methods on copper (111) surface by Toijala [47]. However, from this model, it is difficult to justify the effective high value of the field enhancement factor in the field emission characteristics of a metal surface, as observed in their as well as our present experiments.…”

Section: Discussion On Existing Theories On Ion-irradiated Structure Formation and Field Emission Studiesmentioning

confidence: 99%

Microconical Structure Formation and Field Emission From Atomically Heterogeneous Surfaces Created by Microwave Plasma–Based Low-Energy Ion Beams

Majumdar

Bhattacharjee

2021

Front. Phys.

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We report the formation of self-organized microconical arrays on copper surface when exposed to high flux (5.4 × 1015 cm−2 s−1) of 2 keV argon ion beams at normal incidence. The created microconical arrays are explored for field emission properties. The surface morphologies are investigated by scanning electron microscopy and atomic force microscopy. The local work function variation is analyzed by Kelvin probe force microscopy, and the argon content in the irradiated layer is measured with X-ray Photoelectron Spectroscopy. The average aspect ratio (base width/height) of microstructures for individual irradiated samples is found to increase from 0.7 to 1.5 with a decrease in ion fluence. The ion concentration is highest (3.89 %) for a fluence of 4.7 × 1018 cm−2, which asserts the formation of atomically heterogeneous surface due to subsurface ion implantation. An enhancement in the field emission properties of the argon ion–treated copper substrates at a fluence of 4.7 × 1018 cm−2 with a low turn-on voltage of 2.33 kV and with electron emission current 0.5 nA has been observed. From the Fowler–Nordheim equations, the field enhancement factor is calculated to be 5,561 for pristine copper, which gets enhanced by a factor of 2–8 times for irradiated substrates. A parametric model is considered, by taking into account the modified local work function caused due to structural undulations of the microstructures and presence of implanted argon ions, for explaining the experimental results on the field enhancement factor and emission current.

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“…(c) Investigating the effect of single-atom adsorption and single-atom-defects on otherwise flat surfaces (e.g. [139]). (d) Investigating the electrostatics and emission properties of atomically sharp emitters, such as those developed by Fink [140], and of the three-atom tips used in gas field ion sources for scanning ion microscopy (e.g.…”

Section: Atomistic Electrostatic Modellingmentioning

confidence: 99%

Field emitter electrostatics: a review with special emphasis on modern high-precision finite-element modelling

Assis

Dall’Agnol

Forbes

2022

J. Phys.: Condens. Matter

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This review of the quantitative electrostatics of ﬁeld emitters, covering analytical, numerical and “ﬁtted formula” approaches, is thought to be the ﬁrst of its kind in the 100 years of the subject. The review relates chieﬂy to situations where emitters operate in an electronically ideal manner, and zero-current electrostatics is applicable. Terminology is carefully described and is “polarity independent”, so the review applies to both ﬁeld electron and ﬁeld ion emitters. It also applies more generally to charged, pointed electron-conductors—which exhibit the “electrostatic lightning-rod eﬀect”, but are poorly discussed in general electricity and magnetism literature. Modern electron-conductor electrostatics is an application of the chemical thermodynamics and statistical mechanics of electrons. In related theory, the primary role of classical electrostatic potentials (rather than ﬁelds) becomes apparent. Space and time limitations have meant the review cannot be comprehensive in both detail and scope. Rather, it focuses chieﬂy on the electrostatics of two common basic emitter forms: the needle-shaped emitters used in traditional projection technologies; and the post-shaped emitters often used in modelling large-area multi-emitter electron sources. In the post-on-plane context, we consider in detail both the electrostatics of the single post and the interaction between two identical posts that occurs as a result of electrostatic depolarization (often called “screening” or “shielding”). Core to the review are discussions of the “minimum domain dimensions” method for implementing eﬀective ﬁnite-element-method electrostatic simulations, and of the variant that leads to very precise estimates of dimensionless ﬁeld enhancement factors (error typically less than 0.001 % in simple situations where analytical comparisons exist). Brief outline discussions, and some core references, are given for each of many “related considerations” relevant to the electrostatic situations, methods and results described. Many areas of ﬁeld emitter electrostatics are suggested where further research and/or separate mini-reviews would probably be useful.

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Ab initio calculation of field emission from metal surfaces with atomic-scale defects

Cited by 15 publications

References 74 publications

On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes

On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes

Microconical Structure Formation and Field Emission From Atomically Heterogeneous Surfaces Created by Microwave Plasma–Based Low-Energy Ion Beams

Field emitter electrostatics: a review with special emphasis on modern high-precision finite-element modelling

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Ab initio calculation of field emission from metal surfaces with atomic-scale defects

Cited by 15 publications

References 74 publications

On the evaluation of field emission parameters of V2O5 and TiO2 nanostructure cathodes

On the evaluation of field emission parameters of V2O5 and TiO2 nanostructure cathodes

Microconical Structure Formation and Field Emission From Atomically Heterogeneous Surfaces Created by Microwave Plasma–Based Low-Energy Ion Beams

Field emitter electrostatics: a review with special emphasis on modern high-precision finite-element modelling

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On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes

On the evaluation of field emission parameters of V₂O₅ and TiO₂ nanostructure cathodes