Dependence of Optimum Thickness of Ultrathin Diamond-like Carbon Coatings over Carbon Nanotubes on Geometric Field Enhancement Factor

Abstract

The generation of a field emission (FE) cathode electron source has attracted wide attention for its miniaturization, high-frequency operability, and low energy consumption. However, the FE performance of cold cathodes is limited by poor current stabilities of carbon nanotube (CNT) emitters. Coating CNTs with sp 3 -bonded carbon coatings is considered as a successful approach to stabilize the FE currents. High-quality ultrathin diamond-like carbon (DLC) films, which serve as sp 3 carbon coatings, are deposited uniformly on CNTs by filtered cathodic vacuum arc evaporation in this research. The thicknesses of DLC coatings and the field enhancement factors of pristine CNTs affect to a large extent the FE properties. An optimum coating thickness of DLC layers corresponding to the lowest threshold field exists due to space-charge-induced band bending, at which the depletion region of the DLC layer in equilibrium is maximized. The optimum coating thickness increases with the geometric field enhancement factor of pristine CNTs bundles, the relationship of which illustrates an obvious difference between planar cold cathodes and nanostructured field emitters, and could be extended to optimize double-layer or multi-layered nanostructures serving as FE emitters with high reliability.

Recent Advances of Carbon-Based Flexible Strain Sensors in Physiological Signal Monitoring

“…Polymeric materials are widely used as flexible substrates for flexible sensors due to their excellent flexibility, good thermal stability, and chemical stability, for example, polydimethylsiloxane (PDMS), , Ecoflex, − polyurethane (PU), , polyethylene terephthalate (PET), , polyimide (PI), , rubber, , and so on. Conductive filled materials, such as carbon nanotubes (CNTs), − graphene (including rGO), ,,− metal nanoparticles and nanowires, − conductive polymers, and so on have been intensively studied in recent years. Using the conductive filled nanoparticles, a high sensitivity of sensors was reported to be easy to achieve.…”

Improved Field Emission Properties of Carbon Nanotube Paste Emitters Using an Electrically Conductive Graphite Binder

“…1−4 This is due to the high aspect ratio, 5 excellent electrical conductivity, 6 thermal conductivity, 7 and mechanical strength 8 of the CNTs. Various techniques have been reported for fabricating CNT field electron emitters, by using a CNT tip, 9 as-grown CNTs, 10,11 a CNT yarn, 12 a CNT paste, 13,14 and a CNT film. 15,16 Among the various types of CNT emitters, CNT paste emitters have been widely used due to several advantages, such as a simple fabrication process, strong mechanical adhesion, and large size.…”

“…Carbon nanotubes (CNTs) have attracted much attention as ideal field electron emitters for various vacuum nanoelectronic devices. − This is due to the high aspect ratio, excellent electrical conductivity, thermal conductivity, and mechanical strength of the CNTs. Various techniques have been reported for fabricating CNT field electron emitters, by using a CNT tip, as-grown CNTs, , a CNT yarn, a CNT paste, , and a CNT film. , Among the various types of CNT emitters, CNT paste emitters have been widely used due to several advantages, such as a simple fabrication process, strong mechanical adhesion, and large size. , Typically, to fabricate CNT paste, a mixture of CNTs, fillers, and binder material is screen-printed onto a substrate, and patterns of CNT paste are formed on the substrate after heat treatment. The binder material plays a crucial role in fabricating CNT paste emitters, as they help to fix the CNT networks within the CNT paste.…”

Characterization of Ultra-Thin Diamond-Like Carbon Films by SEM/EDX

“…Many characterization techniques for DLC films have been reported in the literature. Well known techniques are: X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Electron Energy Loss Spectroscopy (EELS), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), and Spectroscopic Ellipsometry (SE) [17][18][19][20]. Each of those techniques has advantages and disadvantages in different aspects.…”