Improved field emission via laser processing of carbon nanotubes on paper substrates

Abstract

Field emission (FE) is the emission of electrons from a solid by the application of a high electric field via quantum mechanical tunneling of electrons through a potential barrier. Carbon nanotubes (CNTs) have excellent FE properties, 1,2,3,4 The morphology of a surface plays a crucial role in determining its FE properties. 15,16 The local field at the emission site governs FE, so micron and nanoscale protrusions can enhance FE due to increased electric field concentration at their surfaces. This enhancement is described by the field enhancement factor (β); the factor by which the local electric field exceeds the macroscopic applied electric field.Therefore, by altering the morphology of an emitter, β and the FE properties can be modified.In this article the deposition of multiwall carbon nanotube ink (MWNT) onto paper substrates via a straightforward dip-coating technique is investigated as a means to increase β by taking advantage of the inherent roughness of the substrate. Paper substrates were chosen as low cost, flexible, readily available materials, and as established substrates for printing technologies. It has already been determined that MWNTs deposited onto paper substrates can have excellent FE properties, which can be tailored according to the morphology of the specific paper substrate utillzed. 17 Here, the effects of a postdeposition excimer laser treatment on the morphology and, therefore, FE characteristics of such samples are investigated.MWNTs with a nominal diameter of 10 nm were purchased from Nanocyl and ultrasonically dispersed in a 3:1 concentrated sulfuric and nitric acid mixture for 10 min. The mixture was refluxed at elevated temperature for 40 min before diluting with de-ionized water. This process results in the formation of carboxylic acid groups attached to the MWNT ends and sidewalls, which interact with water molecules via hydrogen bonding. Large particles and agglomerates were removed from the solution by centrifuging. The centrifuged liquid was carefully decanted, filtered, and washed with de-ionized

Field Emission Cathodes to Form an Electron Beam Prepared from Carbon Nanotube Suspensions

“…This research had an impact on the development of a uniform and large area of FE electron sources formed in a simplified process like dip-coating, drop-casting, or filtration (Figure 5a,b) [98,[100][101][102][103], and finally screen printing (Figure 5c) [104][105][106], which is an established and well-known method for fine patterning, with increasing use for flexible electronics [107][108][109], including vacuum electronics [110,111]. The graph summarizing the techniques for the FE cathodes upon the alignment of the CNTs and the scalability is presented in Figure 6 (author's work).…”

“…Field emission from the sidewalls of CNTs: the voltage-current (I-V) characteristic of films made of CNTs aligned parallel, at 45°, and perpendicular to the substrate (reprinted with permission from[94]). This research had an impact on the development of a uniform and large area of FE electron sources formed in a simplified process like dip-coating, drop-casting, or filtration(Figure 5a,b)[97,[99][100][101][102], and finally screen printing(Figure 5c)[103][104][105], which is an established and well-known Uniform and large area FE cathodes: (a,b) SEM images of the buckypaper surface reprinted with permission from[101] (a) and reprinted with permission from[102] (b); (c) the emission image of the screen-printed FED (reprinted with permission from[104]). …”

The field emission of graphene films reduced by laser treatment

“…Previous studies reported that the FE properties of CNTs [6,7] and other material such as ZnO nanowires [8] would be greatly enhanced after laser treatment. With similar structure, graphene may also have the opportunity to improve the FE properties after laser treatment.…”

Emitter spacing effects on field emission properties of laser-treated single-walled carbon nanotube buckypapers

“…Recently, laser irradiation, post-plasma treatments, and Ar neutral beam treatments have been studied to improve the CNT field emission properties [14][15][16][17][18][19]. Of these, the laser irradiation appears to be the most accurate and rapid method to enhance the emitting performance.…”