2018/12/13 by Oksana Chubenko, Stanislav S. Baturin, Sergey V. Baryshev
Materials Science · Physics and Astronomy · #Charge carrier #Chemical and Physical Properties of Materials #Diamond #Diamond and Carbon-based Materials Research #Electric field #Electron #Electronic and Structural Properties of Oxides #Field electron emission #Impurity #Planar #Saturation (graph theory) #Semiconductor #cond-mat.mtrl-sci
paper · pdf · doi:10.1063/1.5085679
published as Journal of Applied Physics 125(20):205303 2019 · 15 pages, 14 figures
arxiv created 2018/12/13 · openalex created_date 2018/12/22 · openalex publication_date 2019/05/28 · arxiv updated 2019/06/20 · openalex updated_date 2026/08/05
In the nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] films, representing an n-type highly conductive two-phase material comprised of sp3 diamond grains and sp2-rich graphitic grain boundaries, current is carried by a high concentration of mobile electrons within 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 volts per micrometer, which makes it a promising material for designing electron sources. Despite 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 diodelike to a resistorlike behavior. Such a 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) 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 a high electric field. Theoretical calculations are consistent with the experiment.