Direct observation of electron emission from grain boundaries in CVD diamond by PeakForce-controlled tunnelling atomic force microscopy

Harniman, Robert L.; Fox, Oliver; Janssen, Wiebke; Drijkoningen, Sien; Haenen, Ken; May, Paul

doi:10.1016/j.carbon.2015.06.082

Cited by 61 publications

(47 citation statements)

References 39 publications

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“…In particular, hydrogen termination of nitrogenincorporated 150 nm thick layer of UNCD ((N)UNCD:H) was shown to provide a stable work function of 3.1 eV, as well as protection against exposure to air [52]. A potential problem with UNCD, however, is a high degree of EFE [53][54][55], which may be prohibitive for large surface fields (tens of kV/cm); it remains to be demonstrated if a sufficiently strong EFE suppression is possible by tuning the UNCD parameters without, at the same time, paying a penalty of a higher work function. EFE is reported to be very low in single-crystal diamond [55], but it is unclear if this is a practical option for TPCs.…”

Section: Candidate Iisee Target Materials For Gaseous Tpcsmentioning

confidence: 99%

“…A potential problem with UNCD, however, is a high degree of EFE [53][54][55], which may be prohibitive for large surface fields (tens of kV/cm); it remains to be demonstrated if a sufficiently strong EFE suppression is possible by tuning the UNCD parameters without, at the same time, paying a penalty of a higher work function. EFE is reported to be very low in single-crystal diamond [55], but it is unclear if this is a practical option for TPCs. The surface treatment of the above diamond layers provides a sufficiently high conductivity to avoid charging-up.…”

Section: Candidate Iisee Target Materials For Gaseous Tpcsmentioning

confidence: 99%

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On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe

Arazi

2018

J. Phys.: Conf. Ser.

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The neutralization of slow positive ions on solid surfaces can lead to the emission of secondary electrons in Auger-type processes. We discuss the possibility of harnessing such mechanisms to the detection of positive ions in gaseous TPCs. Applied to high pressure xenon, the proposed idea may enable reconstructing with high accuracy the topology of candidate neutrinoless double beta decay events of 136 Xe without sacrificing the energy resolution of pure Xe gas. Candidate secondary electron emitters are discussed, as well as the expected efficiencies, challenges and potential pitfalls.

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Section: Candidate Iisee Target Materials For Gaseous Tpcsmentioning

confidence: 99%

Section: Candidate Iisee Target Materials For Gaseous Tpcsmentioning

confidence: 99%

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe

Arazi

2018

J. Phys.: Conf. Ser.

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confidence: 81%

Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

Chubenko

Baturin

Baryshev

2016

Applied Physics Letters

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The letter introduces a diagram that rationalizes tunneling atomic force microscopy (TUNA) observations of electron emission from polycrystalline diamonds as described in recent publications [1,2]. The direct observations of electron emission from grain boundary sites by TUNA could indeed be evidence of electrons originating from grain boundaries under external electric fields. At the same time, from the diagram it follows that TUNA and field emission schemes are complimentary rather than equivalent for results interpretation. It is further proposed that TUNA could provide better insights into emission mechanisms by measuring the detailed structure of the potential barrier on the surface of polycrystalline diamonds.The question is yet to be answered of why synthetic polycrystalline diamonds (micro-, nano-, or ultra-nanocrystalline diamond, abbreviated MCD, NCD, UNCD) containing a large amount of the carbon sp 2 phase are such excellent electron field emitters. These diamonds have a low threshold (turn-on) electric field ∼10 MV/m and yield significant current densities. A powerful approach, called the graphitic patch model, to explain this behavior was attempted by Cui, Ristein and Ley [3]. It first originated to plausibly explain sub-bandgap photoelectric emission in single-crystal diamond. The main idea was that the surface always has small carbonic (graphitic) phase patches (electron emitters). The work function (4.6 eV) is reduced when the property of negative electron affinity (NEA, which can be as low as −1.3 eV) is induced on the surrounding diamond host surface. Experimentally, the potential barrier [4] of a patch can be as low as 3.0 eV. The model showed excellent agreement with experiments. While the existence of carbon patches on the surface of a single-crystal diamond could be questioned (signatures seen from indirect spectroscopic measurements), in polycrystalline diamonds the carbon sp 2 phase is a separation interlayer between diamond micro-or nano-crystallites (or grains), and can be directly imaged by transmission electron microscopy in large amounts. The carbon interlayer is also called the grain boundary (GB). Recent observations [1,2] have demonstrated that tunneling electron emission originates from GBs. The observations were made by a specialty atomic force microscope equipped with tunneling current measurement capability, abbreviated as TUNA. The authors hypothesized that TUNA measurements should be representative in the conventional field emission case, meaning that GBs emitting in the TUNA scheme should be emitting sites in a field emitter based on a polycrystalline diamond. Nevertheless, they did not provide a straightforward explanation how exactly TUNA represents the field emission mechanism. In this letter, we present a diagram bridging the TUNA scheme results and the conventional field emission scheme. The diagram is based on the graphitic patch model and the usual electrostatics.Panel (a) in the figure illustrates a case in which a GB of a lateral size of 1 nm is brought in contact ...

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“…(N)UNCD is a graphitic rich two-phase material that consists of sp 3 diamond grains and sp 2 graphitic grain boundaries. It has been reported that electron emission (photo-or field-emission) in this and related materials preferentially originates from the grain boundaries 17,18 . Accordingly, a possible explanation for the observed spectral dependence of the MTE is physical and chemical roughness associated with the nano-granularity of the photocathode material.…”

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confidence: 86%

Mean transverse energy of ultrananocrystalline diamond photocathode

Chen

Adhikari

Spentzouris

et al. 2019

Applied Physics Letters

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Nitrogen incorporated ultrananocrystalline diamond ((N)UNCD) could be an enabling material platform for photocathode applications due to its high emissivity. While the quantum efficiency (QE) of UNCD was reported by many groups, no experimental measurements of the intrinsic emittance/mean transverse energy (MTE) have been reported. Here, MTE measurement results for an (N)UNCD photocathode in the photon energy range of 4.41 to 5.26 eV are described. The MTE demonstrates no noticeable dependence on the photon energy, with an average value of 266 meV. This spectral behavior is shown to not to be dependent upon physical or chemical surface roughness and inconsistent with low electron effective mass emission from graphitic grain boundaries, but may be associated with emission from spatially-confined states in the graphite regions between the diamond grains. The combined effect of fast-growing QE and constant MTE with respect to the excess laser energy may pave the way to bright UNCD photocathodes.Photocathode-based RF and pulsed DC guns are bright electron injectors for free electron lasers and advanced time resolved microscopes 1 . Further progress of electron laser and microscopy facilities (improved sensitivity, spatiotemporal resolution, high throughput) largely depends on development and understanding of materials with the potential to be utilized as photocathodes. Photocathode development challenges include achieving simultaneously (i) high QE, (ii) high transverse coherence (meaning low intrinsic emittance/low MTE), (iii) rapid response time.The ratio of the charge to the MTE determines the photocathode brightness, which in many applications is the most critical figure of merit. For a classical metal photocathode such as copper, the Fowler-Dubridge law 2 predicts that the emitted charge is a fast-growing function of excess energy (a power law), where excess energy ∆E is the difference between the laser primary incident photon energy ω and the work function φ defined as ∆E = ω−φ. Dowell and Schmerge 3 have found that the transverse momentum for metals also grows with excess energy as ∼ √ ω − φ. For the latter reason, to attain the highest quality (low divergence) electron beam metal photocathodes are often operated in the near threshold region (having the smallest ∆E, with the primary photon energy nearly matching the work function), although brightness increases with excess energy.A great number of metal and thin film alkali antimonide photocathodes obey the Dowell-Schmerge (DS) model 3-5 . However, some semiconductor photocathodes, e.g. GaAs and PbTe, show various MTE versus excess energy trends that are different from those specific to metals. Negative electron affinity (NEA) GaAs photocathodes 6 , for instance, demonstrate ∼1,000-fold QE increase as the excess energy increases from 0 to about 1 eV while the MTE remains low and nearly constant with the same ∆E range (within measurement precision).(N)UNCD is another example of a NEA photocathode that has high electron conductivity through the bulk of a semi-me...

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Direct observation of electron emission from grain boundaries in CVD diamond by PeakForce-controlled tunnelling atomic force microscopy

Cited by 61 publications

References 39 publications

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe

Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

Mean transverse energy of ultrananocrystalline diamond photocathode

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Direct observation of electron emission from grain boundaries in CVD diamond by PeakForce-controlled tunnelling atomic force microscopy

Cited by 61 publications

References 39 publications

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in 136Xe

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in 136Xe

Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

Mean transverse energy of ultrananocrystalline diamond photocathode

Contact Info

Product

Resources

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On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in ¹³⁶Xe