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An electron field emitter with superior electron field emission (EFE) properties and improved lifetime stability is being demonstrated via the combination of carbon nanotubes and the CH4/N2 plasma grown ultrananocrystalline diamond (N-UNCD) films. The resistance of the carbon nanotubes to plasma ion bombardment is improved by the formation of carbon nanocones on the side walls of the carbon nanotubes, thus forming strengthened carbon nanotubes (s-CNTs). The N-UNCD films can thus be grown on s-CNTs, forming N-UNCD/s-CNTs carbon nanocomposite materials. The N-UNCD/s-CNTs films possess good conductivity of σ = 237 S/cm and marvelous EFE properties, such as low turn-on field of (E0) = 3.58 V/μm with large EFE current density of (Je) = 1.86 mA/cm2 at an applied field of 6.0 V/μm. Moreover, the EFE emitters can be operated under 0.19 mA/cm2 for more than 350 min without showing any sign of degradation. Such a superior EFE property along with high robustness characteristic of these combination of materials are n...

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 sp(3) diamond cores encased by an sp(2) 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 mu m(-1), a high emission current density of 4.2 mA cm(-2) at an applied field of 4.0 V mu m(-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 micro-plasma-based display devices. The authors would like to thank the Research Foundation Flanders (FWO) for providing the financial support via Research Grants 12I8416N and 1519817N, and the Methusalem "NANO" network. K. J. Sankaran is a Postdoctoral Fellow of the Research Foundation-Flanders (FWO). This work was also supported by the Polish National Science Centre (NCN) under Grant No. 2014/14/M/ST5/00715 and 2016/21/B/ST7/01430. The DS funds of Faculty of Electronics, Telecommunications and Informatics of the Gdansk University of Technology are also acknowledged. K. P. and J. Y. P. were supported by the Institute for Basic Science [IBS-R004-A2-2017-a00]. The manuscript was written through contributions of all authors. All authors gave approval to the final version of the manuscript.

Highly efficient with excellent stability electron field emitters based on monolayer graphene coated on well-aligned Si tip (graphene/SiT) arrays fabricated by a simple transfer method are demonstrated. The graphene monolayer is coated on the Si tip array using a chemical vapor deposition process, while the SiTs are prepared through the etching process of a Si substrate. The novel heterostructure field emitter enhanced electron tunneling, as a result, exhibits a better emission property. In addition, the fabricated microplasma devices based on the graphene/SiT heterostructure are closely correlated to the field emission properties of the graphene/SiT materials. The monolayer graphene supported on vertical SiTs provides the protruded nanostructure, which locally enhances the electric field and thus improves the field emission and the plasma illumination characteristics.

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.

Plasma post-treatment (ppt) process for enhancing the electron field emission (EFE) properties of diamond/CNTs films for the applications in triode vacuum field emission (VFE) transistors is being reported. The EFE properties of UNCD/CNTs films were markedly improved by modifying the granular structure by ppt-process. The factor which resulted in enhanced EFE properties is due to the formation of nano-graphitic layers, while the nano-sized diamond grains coalesced. The triode VFE transistors performance was also significantly enhanced due to the utilization of DGC/CNTs (or HiD/CNTs) films as cathode that renders the triode VFE transistors possessing great potential for applications in vacuum microelectronics.

We improved the electron field emission properties of ultrananocrystalline diamond (UNCD) films grown on Si-tip arrays by using the carbon nanotubes (CNTs) as interlayer and post-treating the films in CH4/Ar/H2 plasma. The use of CNTs interlayer effectively suppresses the presence of amorphous carbon in the diamond-to-Si interface that enhances the transport of electrons from Si, across the interface, to diamond. The post-treatment process results in hybrid-granular-structured diamond (HiD) films via the induction of the coalescence of the ultrasmall grains in these films that enhanced the conductivity of the films. All these factors contribute toward the enhancement of the electron field emission (EFE) process for the HiDCNT/Si-tip emitters, with low turn-on field of E0 = 2.98 V/μm and a large current density of 1.68 mA/cm(2) at an applied field of 5.0 V/μm. The EFE lifetime stability under an operation current of 6.5 μA was improved substantially to τHiD/CNT/Si-tip = 365 min. Interestingly, these HiDCNT/Si-tip materials also show enhanced plasma illumination behavior, as well as improved robustness against plasma ion bombardment when they are used as the cathode for microplasma devices. The study concludes that the use of CNT interlayers not only increase the potential of these materials as good EFE emitters, but also prove themselves to be good microplasma devices with improved performance.

Diamond nanostructures (DNSs) were fabricated from three different morphological diamonds, microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films, using a reactive ion etching method. The plasma illumination ( PI) behavior of microplasma devices using the DNSs and the diamond films as cathode were investigated. The Paschen curve approach revealed that the secondary electron emission coefficient (gamma value) of diamond materials is similar irrespective of the microstructure (MCD, NCD, and UNCD) and geometry of the materials (DNSs and diamond films). The diamond materials show markedly larger gamma-coefficient than conventional metallic cathode materials such as Mo that resulted in markedly better PI behavior for the corresponding microplasma devices. Moreover, the PI behavior, i.e. the voltage dependence of plasma current density (J(pl)-V), plasma density (n(e)-V), and the robustness of the devices, varied markedly with the microstructure and geometry of the cathode materials that was closely correlated to the electron field emission (EFE) properties of the cathode materials. The UNCD nanopillars, possessing good EFE properties, resulted in superior PI behavior, whereas the MCD diamond films with insufficient EFE properties led to inferior PI behavior. Consequently, enhancement of plasma characteristics is the collective effects of EFE behavior and secondary electron emission characteristics of diamond-based cathode materials. The authors would like to thank the Ministry of Science and Technology, Republic of China, for the support of this research through the project No. MOST104-2112-M-032-003. Kamatchi Jothiramalingam Sankaran is a Postdoctoral Fellow of the Research Foundation-Flanders (FWO).

In this study we have developed a near Ultra Violet (NUV) source by using discharge of Ar + N 2 gas mixture with employ of DC power source. The cathode materials play vital role in efficiency and lifetime of UV sources, which are attained from micro-discharges of various gas compositions. In the present study, micro discharges are conducted in the cavity, which have been architecture by using cylindrical diamond nanotips cathode and ITO coated glass anode. The NUV emission (330 to 400 nm) from the N 2 (C-B transition) observed at pressure of 10 torr by applying the DC power of 30-120 mW. The NUV emissions have collected by optical emission spectrometer. The NUV emission intensities increased as function of power at constant pressure. Moreover the devices tested at low pressures and powers in non-harsh gas environment.

The enhanced lifetime stability for the carbon nanotubes (CNTs) by coating hybrid granular structured diamond (HiD) films on Au-decorated CNTs/Si using a two-step microwave plasma enhanced chemical vapor deposition process was reported. Electron field emission (EFE) properties of HiD/Au/CNTs emitters show a low turn-on field (E0) of 3.50 V/μm and a high emission current density (Je) of 0.64 mA/cm(2) at an applied field of 5.0 V/μm. There is no notable current degradation or fluctuation over a period of τ(HiD/Au/CNTs) = 360 min for HiD/CNTs EFE emitters tested under a constant current of 4.5 μA. The robustness of the HiD/CNTs EFE emitter is overwhelmingly superior to that of bare CNTs EFE emitters (τ(CNTs) = 30 min), even though the HiD/Au/CNTs do not show the same good EFE properties as CNTs, which are E0 = 0.73 V/μm and Je = 1.10 mA/cm(2) at 1.05 V/μm. Furthermore, the plasma illumination (PI) property of a parallel-plate microplasma device fabricated using the HiD/Au/CNTs as a cathode shows a high Ar plasma current density of 1.76 mA/cm(2) at an applied field of 5600 V/cm with a lifetime of plasma stability of about 209 min, which is markedly better than the devices utilizing bare CNTs as a cathode. The CNT emitters coated with diamond films possessing marvelous EFE and PI properties with improved lifetime stability have great potential for the applications as cathodes in flat-panel displays and microplasma display devices.

Vertically aligned conducting ultrananocrystalline diamond (UNCD) nanorods are fabricated using the reactive ion etching method incorporated with nanodiamond particles as mask. High electrical conductivity of 275 Ω·cm−1 is obtained for UNCD nanorods. The microplasma cavities using UNCD nanorods as cathode show enhanced plasma illumination characteristics of low threshold field of 0.21 V/μm with plasma current density of 7.06 mA/cm2 at an applied field of 0.35 V/μm. Such superior electrical properties of UNCD nanorods with high aspect ratio potentially make a significant impact on the diamond-based microplasma display technology.

The enhancement on the plasma illumination characteristics of a cylindrical microplasma device due to the utilization of hybrid-diamond (HiD) films as cathode was systematically investigated. The improved plasma illumination behavior was closely related to the enhanced electron field emission (EFE) properties of the diamond films. The HiD films, which possessed better EFE properties, including lower turn-on field for inducing the EFE process [(E0)efe = 2.7 V/μm] and higher EFE current density [(Je)efe = 2.8 mA/cm2, at 10.6 V/μm], resulted in superior illumination performance for the microplasma devices. The plasma can be triggered at a low threshold field of (Eth)pl. = 0.166 V/μm, attaining a large plasma current density of (Je)pl. = 9.6 mA/cm2 at an applied field of 0.266 V/μm (plasma density of ne = 1.70 × 1015 cm−3). The better EFE for the HiD films is ascribed to the unique granular structure of the films. Transmission electron microscopic studies revealed that the HiD films contained large diamond ag...