Direct observation of electron emission from CVD diamond grain boundaries by tunnelling atomic force microscopy independent of surface morphology

Harniman, Robert L.; May, Paul; Fox, Oliver

doi:10.1016/j.diamond.2017.09.009

Cited by 10 publications

(6 citation statements)

References 26 publications

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“…Moreover, it should be mentioned that many different groups − have worked on the local EFE behavior of UNCD films and observed that electrons were primarily emitted from the grain boundaries amidst the asperities of diamond surfaces. This occurs because the electrons, which were supplied by the bottom external electrodes (through the substrates), were transported along the path with the smallest resistance in the diamond materials upward to the top surface of the UNCD films and were then emitted there.…”

Section: Results and Discussionmentioning

confidence: 99%

Evolution of Granular Structure and the Enhancement of Electron Field Emission Properties of Nanocrystalline and Ultrananocrystalline Diamond Films Due to Plasma Treatment Process

Chen

Yeh

et al. 2018

ACS Appl. Mater. Interfaces

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The present work reports the plasma post treatment (ppt) process that instigates the evolution of granular structure of nanocrystalline diamond (NCD), consequently conducing the enhancement of the electron field emission (EFE) properties. The NCD films contain uniform and nanosized diamond grains (∼20 nm) with negligible thickness for grain boundaries that is distinctly different from the microstructure of ultrananocrystalline (UNCD) films with uniformly sized ultrananodiamond grains (∼5 nm) having relatively thick grain boundaries (∼0.1 nm). The turn-on of the electron field emission (EFE) process occurs at ( E) = 24.1 V/μm and ( E) = 18.6 V/μm for the pristine NCD and UNCD materials, respectively. The granular structure of the starting diamond films largely influenced the microstructure evolution behavior and EFE properties of the materials subject to plasma annealing. The CH/(Ar-H) ppt-process leads to formation of a hybrid granular structured diamond (HiD and HiD) via isotropic conjoining of nanosized diamond grains, whereas the CH/N ppt-process leads to the formation of acicular granular structured diamond films (N and N) via inducing aeolotropic growth of nanodiamond grains. While both of the HiD and HiD films contain hybrid granular structure, the HiD films contain a larger proportion of nanographite phase and result in improved EFE properties, viz. ( E) = 7.7 V/μm and ( E) = 12.3 V/μm. In contrast, when the films were CH/N ppt-processed, the acicular diamond grains were formed for N and N films; however, carbon nanoclusters attached to the diamond grains of N films and the nanographitic layers encasing diamond cores are not crystallized very well, as compared with N films. Therefore, the N films exhibit slightly inferior EFE properties than the N films, viz. ( E) = 5.3 V/μm and ( E) = 11.8 V/μm. The difference in EFE properties for ppt-processed NCD and UNCD films corresponds to the dissimilar granular structure evolution behavior in these films that is, in turn, due to the distinct different microstructure of the pristine NCD and UNCD films.

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Section: Results and Discussionmentioning

confidence: 99%

Evolution of Granular Structure and the Enhancement of Electron Field Emission Properties of Nanocrystalline and Ultrananocrystalline Diamond Films Due to Plasma Treatment Process

Chen

Yeh

et al. 2018

ACS Appl. Mater. Interfaces

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“…It is known that the grain boundary density in a polycrystalline diamond thin film increases as the grain size decreases, leading to enhancement of the intensity of the bands derived from sp 2 carbon impurities. [40][41][42] The results of particle size, conductivity, BET specific surface area, and Raman spectra suggest that nanocrystalline BDD layer was grown on the surface of BDDP-150. Thus, we confirmed that a conductive diamond powder with high specific surface area was obtained by this procedure.…”

Section: Resultsmentioning

confidence: 99%

Boron-Doped Diamond Powders for Aqueous Supercapacitors with High Energy and High Power Density

Kondo

Kato

Miyashita

et al. 2019

J. Electrochem. Soc.

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The electrochemical properties of boron-doped diamond powder (BDDP) were investigated as a step toward its application to aqueous electric double-layer capacitors (EDLCs). Conductive BDDPs (particle size: 150, 350, and 3500 nm) were prepared by depositing a BDD layer on the surface of a diamond powder (DP) core with various particle sizes (100, 300, and 2600 nm) via microwave plasma-assisted chemical vapor deposition. The 150-nm-sized BDDP (BDDP-150) had a relatively large Brunauer-Emmett-Teller (BET) specific surface area (106 m 2 /g). Cyclic voltammetry of the BDDP electrodes in 1.0 M H 2 SO 4 with a symmetric two-electrode system showed an operating voltage of 1.5 V, which is much larger than that of an activated carbon (AC) electrode (0.8 V). In addition, compared to the AC electrode, the BDDP electrodes showed lower capacitance-decrease ratios at fast scan rates. Hence, BDDP-150 had greater energy and power densities than the AC electrode under high rate conditions in the aqueous electrolyte. As the BDDP electrode had a larger bulk density than the AC electrode, aqueous EDLC using BDDP can be expected to be used as a space-saving electric energy storage system suitable for high-speed charging and discharging.

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“…The nanoscale sp 2 -carbon inclusions situated in grain boundaries locally lower the barrier for emission. Thus, field emission is believed to originate mainly from the grain boundaries surrounding crystallites rather than from the top of the grains [46,47].…”

Section: Emitter Surface Morphologymentioning

confidence: 99%

“…The inclusion of grain boundaries generally assists with emission by improving electron transport to the surface. Indeed, for field emission it is now believed that the electron emission originates from grain boundaries at the surface which lower the local effective barrier to emission in the presence of an electric field [46,47]. However, thermionic emission does not utilise a significant applied field, and so this mechanism will not apply.…”

Section: Thermionic Emission From Diamondmentioning

confidence: 99%

A review of surface functionalisation of diamond for thermionic emission applications

James

Fogarty

Zulkharnay

et al. 2021

Carbon

Self Cite

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Direct observation of electron emission from CVD diamond grain boundaries by tunnelling atomic force microscopy independent of surface morphology

Cited by 10 publications

References 26 publications

Evolution of Granular Structure and the Enhancement of Electron Field Emission Properties of Nanocrystalline and Ultrananocrystalline Diamond Films Due to Plasma Treatment Process

Evolution of Granular Structure and the Enhancement of Electron Field Emission Properties of Nanocrystalline and Ultrananocrystalline Diamond Films Due to Plasma Treatment Process

Boron-Doped Diamond Powders for Aqueous Supercapacitors with High Energy and High Power Density

A review of surface functionalisation of diamond for thermionic emission applications

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