Vertically Aligned Carbon Nanotube Microbundle Arrays for Field-Emission Applications

Abstract

The fabrication, properties, and applications of vertically aligned carbon nanotube (VACNT) microbundle arrays with different length-to-diameter ratios were investigated. VACNT microbundle arrays with different length-to-diameter ratios from 4:1 to 30:1 and microscaling of carbon nanotube blocks were fabricated using pulsed laser ablation technology. These VACNT microbundle arrays had a very low threshold field (0.117 V/μm), excellent time stability, and high field emission current densities (137.91 A/cm2). These values are superior to those of carbon nanotubes grown directly on a silicon substrate. The large length-to-diameter ratio and the small diameter of the VACNT microbundles are considered to be the main reasons for the excellent field emission performance.

Nanocone-Shaped Carbon Nanotubes Field-Emitter Array Fabricated by Laser Ablation

“…The formation of the final shape of the groove processed on VACNT is the result of the accumulation of multiple energy points with Gaussian distribution following different characteristics in space. According to our research on laser processing parameters (Supplementary Materials) and the previous reports of Tang [20] et al, after multiple pulses, the shapes of grooves processed on VACNT are not the same, one of which is triangular. The nanoscale edges can be obtained by accurately controlling the position of two adjacent triangular machining grooves, as shown Field-emission measurements were carried out in a custom-built vacuum chamber evacuated to a base pressure of <1 × 10 −7 mbar.…”

“…In brief, macroscale 2 mm × 2 mm square monoliths of VACNT thin films, which were ready for subsequent UV laser processing were synthesized on silicon substrate by PECVD (plasma-enhanced chemical vapor deposition) [11,[16][17][18]. Respectively, as shown in Figure 1a,b, femtosecond laser processing has been demonstrated elsewhere though commonly at different wavelengths such as 800 nm and 1064 nm [19][20][21]; however, in the present work, a nanosecond ultraviolet laser processing platform (λ = 355 nm, Suzhou Delong laser Co. Ltd., Suzhou, China; FP-D-DZS-001) was used. AutoCAD (Version 2018, Autodesk, Inc., Mill Valley, CA, USA) software was used in this work to create DGW files required by the laser patterning system.…”

“…It has been shown elsewhere that micro and macro-scale geometries within CNT arrays enhanced their field electron emission performances [19][20][21]. Thus, here, we explored the use of the developed patterning technique to engineer new electron emission sources.…”

Effects of Interfacial Electron Transport on Field Electron Emission from Carbon Nanotube Paste Emitters

“…Because the field emission (FE) source is based on a physical mechanism, in which electrons are quantum mechanically tunneled by the applied voltage, it has superior advantages with fast and accurate current controls compared to thermionic emission. − Recently, studies have been actively performed on the FE source to improve the performance of its X-ray applications, such as medical diagnosis and industrial inspection. − Among these studies, the main theme is to maximize the FE current because the insufficiency of the emission current limits the applicability for the X-ray devices that require high dose like radiography and computed tomography for medical and in-line inspection for industrial applications. , In terms of high emission current, carbon nanotube (CNT) is suitable as a material for the field emitter due to its high electrical and thermal conductivities, great mechanical strength, and high aspect ratio, and it is being actively studied at present. − Many researchers have focused on intrinsic parameters, including the work function and the aspect ratio of CNT emitters to improve the emission efficiency. − However, the extrinsic parameters of emitters that affect the FE property should be considered as well as intrinsic ones; extrinsic parameters include an adhesion property of the CNT emitters onto a cathode substrate and an electron transport property from the cathode substrates to emission sites.…”

Vertically Aligned Boron-Doped Diamond Hollow Nanoneedle Arrays for Enhanced Field Emission

“…To date, the search for innovative electron emission devices for these applications continues. Compared to metals and commercial semiconductors, carbon materials with nanostructures such as carbon nanotubes (CNTs), carbon nanosheets, nanodiamonds, and graphene show enhanced field electron emission (FEE) characteristics. − Generally, a low turn-on electric field ( E TO ), a low threshold electric field ( E THR ), a high maximum current density ( J max ), a large field enhancement factor (β), high stability, and a long lifetime for success of a material as a field emitter are very difficult to obtain in a single material . For example, along with the sharp edges and high aspect ratio for strongly improving the locally enhanced electric field strength arising from nanoscale geometric field enhancement, CNTs and graphene provide low E TO and E THR .…”