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arXiv · 1812.05726

Theoretical Evaluation of Electronic Density-of-states and Transport Effects on Field Emission from $n$-type Ultrananocrystalline Diamond Films

Oksana Chubenko·Stanislav S. Baturin·Sergey V. Baryshev
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Abstract

In the nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) films, representing an $n$-type highly conductive two-phase material comprised of $sp^3$ diamond grains and $sp^2$-rich graphitic grain boundaries, the current is carried by a high concentration of mobile electrons within the large-volume grain boundary networks. Fabricated in a simple thin-film planar form, (N)UNCD was found to be an efficient field emitter capable of emitting a significant amount of charge starting at the applied electric field as low as a few V/$μ$m which makes it a promising material for designing electron sources. Despite the semimetallic conduction, field emission (FE) characteristics of this material demonstrate a strong deviation from the Fowler-Nordheim law in a high-current-density regime when (N)UNCD field emitters switch from a diode-like to resistor-like behavior. Such phenomenon resembles the current-density saturation effect in conventional semiconductors. In the present paper, we adapt the formalism developed for conventional semiconductors to study current-density saturation in (N)UNCD field emitters. We provide a comprehensive theoretical investigation of ($i$) the influence of partial penetration of the electric field into the material, ($ii$) transport effects (such as electric-field-dependent mobility), and ($iii$) features of a complex density-of-states structure (position and shape of $π-π^*$ bands, controlling the concentration of charge carriers) on the FE characteristics of (N)UNCD. We show that the formation of the current-density saturation plateau can be explained by the limited supply of electrons within the impurity $π-π^*$ bands and decreasing electron mobility in high electric field. Theoretical calculations are consistent with experiment.

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Oksana Chubenko, Stanislav S. Baturin, Sergey V. Baryshev. 2018-12-13. Theoretical Evaluation of Electronic Density-of-states and Transport Effects on Field Emission from $n$-type Ultrananocrystalline Diamond Films. https://doi.org/10.1063/1.5085679

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