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Keyword: Welded Braids (1)	3 Apr 2025	Run
Keyword: Field Emitter (3)	3 Apr 2025	Run
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articleNo Access
SIMULATION OF HIGH CURRENT FIELD EMISSION FROM VERTICALLY WELL-ALIGNED METALLIC CARBON NANOTUBES
- W. S. KOH and
- L. K. ANG
International Journal of Nanoscience01 Aug 2004
Preview Abstract
We have studied the intense electron beams emitted from multiple metallic, vertical and well-aligned Carbon Nanotube (CNT) field emitters. A two-dimensional (2D) particle-in-cell simulation code MAGIC2D is used to obtain the I–V characteristics near to the apex of the emitters' surface for a given applied electric field and field enhancement factor over a wide range of parameters. The effects of electron space charge and electric field shielding from neighboring emitters are compared in low current and high current regimes. It is found that the electron space charge is dominant in high current regime, where the Fowler–Nordheim (FN) law becomes the 2D Child–Langmuir (CL) law. The emitter spacing, number of emitters, and emitter's uniformity are also particularly studied, and they are more critical in low current regime. Smooth transition from the FN law to CL law is demonstrated.
articleNo Access
FABRICATION AND ELECTRON MICROSCOPY CHARACTERIZATION OF METAL-GATED CARBON NANOTUBE EMITTER ARRAYS
- JIANFENG WU,
- LIFENG DONG,
- JEREMY PETTY,
- CHIACHING PAN, and
- JUN JIAO
International Journal of Nanoscience01 Aug 2006
Preview Abstract
A technique was investigated for the fabrication of triode-type carbon nanotube (CNT) field emitter arrays, where an integrated extraction gate was built between the nanotube cathode and the anode. The gate improves the control capability of emission currents. To fabricate the metal-gated CNT field emitter arrays, well ordered cells were generated by focused ion beam (FIB) milling of platinum (Pt) coated silicon (Si) substrate and then modified by chemical etching. Two types of catalyst elements iron (Fe) and nickel (Ni), were used for growing the CNTs inside the cells. The methods for depositing catalysts into the cells include spin coating sol–gel Fe, FIB induced decomposition of ferrocene and sputter coating pure Ni. CNT growth was carried out by a chemical vapor deposition (CVD) process. The results suggest that the CNTs grew from inside the cells where the catalysts were located. In comparison, the CNTs synthesized from the sol–gel Fe catalyst were straighter than those from ferrocene Fe and pure Ni. The density and orientation of the CNTs in each cell are directly related to the type and quantity of the catalysts and are also affected by the size of the cells.
articleNo Access
Synergistic Effect of Field Emission Properties on Growth of CNTs by One-Pot Preparation of Various Concentrations Composite Catalyst
Nano01 May 2022
Preview Abstract
Multi-walled carbon nanotubes (MWCNTs) were grown on Silicon (Si) substrate by using low-pressure chemical vapor deposition (LPCVD) technique where iron (Fe) and silver (Ag) colloidal solution act as a catalyst were prepared by chemical route. The as-prepared solutions in varied concentrations were deposited on a Si substrate using a spin coating process at 700rpm. The purpose of Fe in composite catalysts is to have high carbon solubility and diffusion rate, and Ag utilization can change catalyst activity temperature and enhance carbon yields. In this work, we demonstrate the growth of carbon nanotubes (CNTs) on different catalyst concentrations ( $_{0.025 M}$ $_{0.025 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag), ( $_{0.050 M}$ $_{0.050 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag), ( $_{0.075 M}$ $_{0.075 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) and ( $_{0.100 M}$ $_{0.100 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalytic films. Field Emission Scanning Electron Microscopy (FESEM) was used to image the morphologies of various catalyst concentrations MWCNTs. The natures of the synthesized CNTs were determined using Raman spectroscopy and it was revealed that as-prepared CNTs are MWCNTs due to the absence of radial breathing mode (RBM). Raman spectroscopy demonstrated the lower I_D/I_G ratio (Ratio of the intensity of D-Raman peak and G-Raman peak) of ( $_{0.025 M}$ $_{0.025 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) MWCNTs. The I_D/I_G ratio for ( $_{0.025 M}$ $_{0.025 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs was 0.76, while the I_D/I_G ratio for ( $_{0.100 M}$ $_{0.100 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs was 0.89. The ( $_{0.100 M}$ $_{0.100 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs were found to be more defective as compared to other. Electron Emission from ( $_{0.025 M}$ $_{0.025 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs were much stronger than from other samples, as demonstrated by Field Emission measurement using diode configuration. The turn-on field for ( $_{0.025 M}$ $_{0.025 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs was (0.92 V/ $μ$ $μ$ m) which is slightly lower than that of ( $_{0.100 M}$ $_{0.100 M}$ Fe/ $_{0.100 M}$ $_{0.100 M}$ Ag) catalyzed MWCNTs (1.83 V/ $μ$ $μ$ m), indicating superior enhancement.