Interpretation of field emission current–voltage data: Background theory and detailed simulation testing of a user-friendly webtool

Allaham, Mohammad M.; Forbes, Richard G.; Knápek, Alexandr; Sobola, Dinara; Burda, D; Sedlák, Petr; Mousa, Marwan S.

doi:10.1016/j.mtcomm.2022.103654

Cited by 14 publications

(15 citation statements)

References 23 publications

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“…To deal formally with this situation, for electronically ideal systems, a prediction uncertainty factor (previously called a "knowledge uncertainty factor") has been introduced (e.g., see [5]). The treatment here aligns with that in [18], is more complete than given previously, and supersedes earlier discussions.…”

Section: Relevant Elements Of Field Electron Emission Theorysupporting

confidence: 79%

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

Assis¹,

Dall’Agnol²,

Forbes³

2022

Preprint

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This review of the quantitative electrostatics of field emitters, covering analytical, numerical and "fitted formula" approaches, is thought 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 that 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 that 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 of this 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" that are 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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Section: Relevant Elements Of Field Electron Emission Theorysupporting

confidence: 79%

“…However, applying these procedures to non-ideal systems can generate spurious LVCL values [26]. (Also see [18]. )…”

Section: Field-voltage Relationshipsmentioning

confidence: 99%

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

Assis¹,

Dall’Agnol²,

Forbes³

2022

Preprint

Self Cite

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“…(2) The Orthodoxy Test. This is well described in the literature 3,16 . Essentially, the procedure tests, for the given emitter, whether the apparent operating range of characteristic local fields FC, as derived from a FN or similar data plot is physically reasonable, as compared with well-established operating ranges for metal emitters.…”

Section: A Overviewsupporting

confidence: 66%

“…For FE systems behaving orthodoxly, traditional data-analysis methodology works "more-or-less adequately" (if up-to-date emission theory is used). However, as discussed elsewhere 16 , improved modern versions of data-analysis theory (e.g., the…”

Section: Electronically Ideal Fe Systems and Orthodoxymentioning

confidence: 99%

Proposal that interpretation of field emission current–voltage characteristics should be treated as a specialized form of electrical engineering

Forbes

2023

Journal of Vacuum Science &Amp; Technology B

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This article proposes that we should think differently about predicting and interpreting measured field electron emission (FE) current–voltage [ Im( Vm)] characteristics. It is commonly assumed that Im( Vm) data interpretation is a problem in emission physics and related electrostatics. Many experimentalists then apply the Fowler–Nordheim plot methodology, developed in 1929. However, with modern emitting materials, this 90-year-old interpretation methodology often fails (maybe in nearly 50% of cases) and yields spurious values for characterization parameters, particularly field enhancement factors. This has generated an unreliable literature. Hence, validity checks on experimental Im( Vm) data are nearly always needed before use. A new check, supplementing existing checks, is described. Twelve different “system complications” that, acting singly or in combinations, can cause validity-check failure are identified. A top-level path forward from this unsatisfactory situation is proposed. The term “field electron emission system (FE system)” is defined to include all aspects of an experimental system that affect the measured Im( Vm) characteristics. The analysis of FE systems should now be regarded as a specialized form of electronic/electrical engineering, provisionally called “FE Systems Engineering.” In this approach, the Im( Vm) relationship is split as follows: (a) the current is expressed as a function Im( FC) of the local surface-field magnitude FC at some defined emitter surface location “C,” and (b) the relationship between FC and measured voltage Vm is expressed and determined separately. Determining Im( FC) is mostly a problem in emission physics. Determining the relationship FC( Vm) depends on system electrostatics and (for systems failing a validity check) on the other aspects of FE Systems Engineering, in particular, electrical-circuit modeling. The scope of FE Systems Engineering and some related research implications and problems are outlined.

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“…What useful information can be extracted from those plots remains an open question 29,32 . Very recently, a rather versatile webtool has been presented for data interpretation 33 , but a simple version of the MG theory was used. In a preceding article 32 we showed that even for a flat emitter, some discrepancies between the different levels of approximations in standard field emission models might have an important impact on data analysis.…”

Section: And Then Came Micro and Nanotechnologymentioning

confidence: 99%

All field emission experiments are noisy, {\ldots} are any meaningful?

Ayari,

Vincent,

Perisanu

et al. 2023

Preprint

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Representing field emission data on a Fowler-Nordheim plot is both very common and strongly not recommended. It leads to a spurious estimation of the emitter parameters despite a very good data fit. There is a lack of a reliable method of analysis and a proper estimation of the uncertainty in the extracted parameters. In this article, we show that the uncertainty in the estimation of the field enhancement factor or the emission area can be as high as ±50% even for a tungsten single emitter in good ultra-high vacuum conditions analyzed by the Murphy-Good model. Moreover, the choice of the exact Murphy-Good method can have a noticeable impact. We found that advanced analysis methods, based on the measurement of the differential conductance of the emitter, are so demanding in terms of emitter stability that up to now its requirements are probably out of reach in any field emission laboratory.

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Interpretation of field emission current–voltage data: Background theory and detailed simulation testing of a user-friendly webtool

Cited by 14 publications

References 23 publications

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

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

Proposal that interpretation of field emission current–voltage characteristics should be treated as a specialized form of electrical engineering

All field emission experiments are noisy, {\ldots} are any meaningful?

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