Synthesis of ultra-nano-carbon composite materials with extremely high conductivity by plasma post-treatment process of ultrananocrystalline diamond films

Abstract

Needle-like diamond grains encased in nano-graphitic layers are an ideal granular structure of diamond films to achieve high conductivity and superior electron field emission (EFE) properties. This paper describes the plasma post-treatment (ppt) of ultrananocrystalline diamond (UNCD) films at low substrate temperature to achieve such a unique granular structure. The CH4/N2 plasma ppt-processed films exhibit high conductivity of σ = 1099 S/cm as well as excellent EFE properties with turn-on field of E0 = 2.48 V/μm (Je = 1.0 mA/cm2 at 6.5 V/μm). The ppt of UNCD film is simple and robust process that is especially useful for device applications.

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

“…Conversely, CH 4 /N 2 plasma containing primarily the C 2 and CN species tends to induce aleotropic growth of diamond. The latter post-treatment process can thus prompt the creation of acicular diamond grains, which can even more significantly enhance the EFE properties of the films. , While it is observed that postannealing plasma treatment (ppt) of diamond films can effectively furnish the UNCD films with improved conductivity and greatly enhance the EFE performance of the materials. It is of great technological importance to understand whether or not such kind of ppt-process can also be applied for enhancing conductivity/EFE properties of nanocrystalline diamond films, which possess different granular structure.…”

A nanodispersion-in-nanograins strategy for ultra-strong, ductile and stable metal nanocomposites

“…1d indicates that the carbon nanoparticles have an average diameter of 2.6 ± 1.2 nm and a number fraction of ~92% inside grains as opposed to at GBs. Because of their extremely small sizes (<5 nm), the carbon nanoparticles are referred to as ultra-nano-carbon (unc) 18 . We demonstrated the efficacy of this dispersion strategy by experimenting less-defective nanocarbon (including 1D nanotubes and 2D nanosheets, see Methods) in nanograins; correspondingly, most nanocarbon was found at GBs, likely due to the weak bonding between metal and less-defective nanocarbon that results in easy sliding of nanocarbon on metal surfaces (Supplementary Fig.…”

Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

“…Figure 1c shows that CH 4 /N 2 PPT process contains primarily the C 2 and CN species, confirming the anisotropic growth of grains in HF-UNCD films, as the reported results in other studies. [17,18] This induces a growth along one direction, so the grains in the surface of N HF-UNCD sample become longer comparative with those of the pristine HF-UNCD sample. Figure 1d shows the bias current during the CH 4 /N 2 PPT process, which represents the electrons emitted from diamond due to the negative bias voltage applied to the Si substrates.…”

“…It was reported that the plasma post‐treatment (PPT) process, which was not a process of growing the film directly, but coalescence to form large diamond grains under CH 4 /H 2 /Ar plasma with large content of H 2 [ 15,16 ] or regrowth of needle‐like diamond grains under CH 4 /N 2 plasma [ 17,18 ] on the prepared film, can effectively reduce the temperature requirements on the substrate. [ 15–18 ] Yeh [ 17 ] and Sankaran [ 18 ] observed that the CH 4 /N 2 plasma mainly contained C 2 and CN species and induced anisotropic growth of grains in UNCD films, resulting in the formation of needle‐like diamond grains that markedly enhanced the EFE properties of the films. This effectively rendered the UNCD films more conductive and greatly enhanced the EFE properties of the materials without additional heater equipped.…”