Development of long lifetime cathode materials for microplasma application

[[abstract]]In this paper we present the growth of three kinds of diamond films including ultrananocrystalline diamond (UNCD), nitrogen doped UNCD and hybrid granular structured diamond (HiD) films on Au coated silicon for applying as a cathode in a parallel-plate type microplasma device. The phase constituents and microstructures of these diamond films were investigated in order to understand the role of the intrinsic properties of these cathode materials on manipulation of the plasma characteristics of the corresponding devices. We observed that, while the diamond materials with a high fraction of sp2-bonded carbons exhibited superior electron field emission (EFE) properties and hence better plasma illumination (PI) behavior, the cathode materials with a suitable microstructure are required to ensure longer lifetime for practical applications of the microplasma devices. Based on these observations, we have developed hybrid granular structured diamond films, in which the sp2-bonded carbons were hidden in the boundaries between the sp3-bonded diamond grains, such that the films exhibited not only excellent EFE properties and PI behavior but also good PI behavior with long lifetime.[[journaltype]]國外[[booktype]]電子版[[countrycodes]]GB

The microstructural evolution of ultrananocrystalline diamond films due to P ion implantation process—the annealing effect

[[abstract]]The microstructural evolution of UNCD films which are P-ion implanted and annealed at 600 °C (or 800 °C) is systematically investigated. The difference of interaction that the UNCD content undergoes along the trajectory of the incident P-ions is reflected in the alteration of the granular structure. In regions where the P-ions reside, the “interacting zone,” which is found at about 300 nm beneath the surface of the films, coalescence of diamond grains occurs inducing nano-graphitic clusters. The annealing at 600 °C (or 800 °C) heals the defects and, in some cases, forms interconnected graphitic filaments that result in the decrease in surface resistance. However, the annealing at 600 °C (800 °C) induces marked UNCD-to-Si layers interaction. This interaction due to the annealing processes hinders the electron transport across the interface and degrades the electron field emission properties of the UNCD films. These microstructural evolution processes very well account for the phenomenon elaborating that, in spite of enhanced conductivity of the UNCD films along the film's surface due to the P-ion implantation and annealing processes, the electron field emission properties for these UNCD films do not improve.[[notice]]補正完畢[[booktype]]紙本[[countrycodes]]US

Boron-Doped Nanocrystalline Diamond-Carbon Nanospike Hybrid Electron Emission Source

Copyright © 2019 American Chemical Society.Electron emission signifies an important mechanism facilitating the enlargement of devices that have modernized large parts of science and technology. Today, the search for innovative electron emission devices for imaging, sensing, electronics, and high-energy physics continues. Integrating two materials with dissimilar electronic properties into a hybrid material is an extremely sought-after synergistic approach, envisioning a superior field electron emission (FEE) material. An innovation is described regarding the fabrication of a nanostructured carbon hybrid, resulting from the one-step growth of boron-doped nanocrystalline diamond (BNCD) and carbon nanospikes (CNSs) by a microwave plasma-enhanced chemical vapor deposition technique. Spectroscopic and microscopic tools are used to investigate the morphological, bonding, and microstructural characteristics related to the growth mechanism of these hybrids. Utilizing the benefits of both the sharp edges of the CNSs and the high stability of BNCD, promising FEE performance with a lower turn-on field of 1.3 V/μm, a higher field enhancement factor of 6780, and a stable FEE current stability lasting for 780 min is obtained. The microplasma devices utilizing these hybrids as a cathode illustrate a superior plasma illumination behavior. Such hybrid carbon nanostructures, with superb electron emission characteristics, can encourage the enlargement of several electron emission device technologies11sciescopu

Investigations on Diamond Nanostructuring of Different Morphologies by the Reactive-Ion Etching Process and Their Potential Applications

We report the systematic studies on the fabrication of aligned, uniform, and highly dense diamond nanostructures from diamond films of various granular structures. Self-assembled Au nanodots are used as a mask in the self-biased reactive-ion etching (RIE) process, using an O₂/CF₄ process plasma. The morphology of diamond nanostructures is a close function of the initial phase composition of diamond. Cone-shaped and tip-shaped diamond nanostructures result for microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films, whereas pillarlike and grasslike diamond nanostructures are obtained for Ar-plasma-based and N₂-plasma-based ultrananocrystalline diamond (UNCD) films, respectively. While the nitrogen-incorporated UNCD (N-UNCD) nanograss shows the most-superior electron-field-emission properties, the NCD nanotips exhibit the best photoluminescence properties, viz, different applications need different morphology of diamond nanostructures to optimize the respective characteristics. The optimum diamond nanostructure can be achieved by proper choice of granular structure of the initial diamond film. The etching mechanism is explained by in situ observation of optical emission spectrum of RIE plasma. The preferential etching of sp²-bonded carbon contained in the diamond films is the prime factor, which forms the unique diamond nanostructures from each type of diamond films. However, the excited oxygen atoms (O*) are the main etching species of diamond film

Toward high-performance solution-processed carbon nanotube network transistors by removing nanotube bundles

Reported solution-processed field-effect transistor (FET) devices based on single-walled carbon nanotube (SWNT) networks have either high mobility but low on/off ratio or vice versa. Recently, Arnold et al. (Nat. Nanotechnol. 2006, 1, 60−65) have made significant improvements in obtaining semiconductor-enriched SWNTs by using density-gradient ultracentrifugation. Here, we report that removing the SWNT bundles using organic−aqueous interfacial purification can further enhance the electrical performance of SWNT-FETs. The on/off ratio of the SWNT-FET is improved by 1 order of magnitude. By combining density-gradient ultracentrifugation and interfacial purification, it is possible to obtain high on/off ratio and high mobility of solution-processed SWNT-FETs at a promising yield.Accepted versio

Self-organized multi-layered graphene-boron-doped diamond hybrid nanowalls for high-performance electron emission devices

Carbon nanomaterials such as nanotubes, nanoflakes/nanowalls, and graphene have been used as electron sources due to their superior field electron emission (FEE) characteristics. However, these materials show poor stability and short lifetimes, which prevent their use in practical device applications. The aim of this study was to find an innovative nanomaterial possessing both high robustness and reliable FEE behavior. Herein, a hybrid structure of self-organized multi-layered graphene (MLG)-boron doped diamond (BDD) nanowall materials with superior FEE characteristics was successfully synthesized using a microwave plasma enhanced chemical vapor deposition process. Transmission electron microscopy reveals that the as-prepared carbon clusters have a uniform, dense, and sharp nanowall morphology with sp3 diamond cores encased by an sp2 MLG shell. Detailed nanoscale investigations conducted using peak force-controlled tunneling atomic force microscopy show that each of the core-shell structured carbon cluster fields emits electrons equally well. The MLG-BDD nanowall materials show a low turn-on field of 2.4 V μm-1, a high emission current density of 4.2 mA cm-2 at an applied field of 4.0 V μm-1, a large field enhancement factor of 4500, and prominently high lifetime stability (lasting for 700 min), which demonstrate the superiority of these materials over other hybrid nanostructured materials. The potential of these MLG-BDD hybrid nanowall materials in practical device applications was further illustrated by the plasma illumination behavior of a microplasma device with these materials as the cathode, where a low threshold voltage of 330 V (low threshold field of 330 V mm-1) and long plasma stability of 358 min were demonstrated. The fabrication of these hybrid nanowalls is straight forward and thereby opens up a pathway for the advancement of next-generation cathode materials for high brightness electron emission and microplasma-based display devices. © 2018 The Royal Society of Chemistry1231sciescopu