Field emission from multi-walled carbon nanotubes and its application to electron tubes

Abstract

Field emission from closed and open-ended multiwalled nanotubes (MWNTs) was studied by field-emission microscopy. As an application of nanotube field emitters, we manufactured lighting elements with the structure of a triodetype vacuum tube by replacing the conventional thermionic cathodes with the MWNT field emitters. Stable electron emission, adequate luminance and long life of the tubes have been demonstrated.Carbon nanotubes [1] have been attracting considerable attention not only because of their unique physical properties but also because of their applications in composite materials [2] and as elements of electronic devices [3-6] and nanoprobes [7]. Multi-walled nanotubes (MWNTs) [1,8], comprising from 2 to 30 concentric graphitic layers, have outer diameters from 10 to 50 nm, and lengths more than 10 µm. On the other hand, single-walled carbon nanotubes (SWNTs) [9-11] are much thinner, being 1.0 to 1.4 nm in diameter, and of length 100 µm [12]. The high aspect ratio and the small radii of curvature at their tips are realized in carbon nanotubes. The geometric characteristic of nanotubes, together with a high chemical stability and a high mechanical strength [13,14], is advantageous for field emitters. Indeed, field emission (FE) from an individual MWNT [3] and from assemblies of MWNTs [15,16] has been demonstrated. Fieldemission microscopy (FEM) was also performed recently for both MWNT [5] and SWNT [17]. We present here our FEM results obtained for open-ended and closed MWNTs.Based on our study on FE from MWNTs, we have manufactured electron tubes equipped with MWNT field emitters as a cathode. The fabricated tubes (20 mm diameter, 74 mm length) are the three-electrode type, consisting of a cathode (nanotube field emitter arrays), a grid, and an anode (phosphor screen). The manufactured tubes are lighting elements, which are assembled to form a giant outdoor display. Stable electron emission, adequate luminance and long life of the tubes were obtained.

Template-based synthesis of nanomaterials

“…A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made [132]. Cathode ray tubes (as lighting elements) equipped with field emitters composed of MWCNTs have been already manufactured [133].…”

Field emission from carbon nanotubes: perspectives for applications and clues to the emission mechanism

“…It is extremely encouraging to see that such devices incorporating nanotubes have already been demonstrated, by Saito et al [15] for cathode ray tubes and by Wang et al [12] for a 32 × 32 pixel display. With the progress made in the catalytic growth of nanotubes, which permits a patterned growth on a substrate [16], and with the excellent field emission properties of nanotube films that will be outlined below, there is little doubt that commercial devices based on carbon nanotubes electron sources will one day hit the market.…”

“…For example, they have proven to be extremely stiff and resistant to bending [3], and their suitability as a tip for scanning probe microscopy has been demonstrated [4]. They also rank among the best electron field emitters that are now available [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications

“…Figure 13c,d shows SEM images of the motor, which consists of a plate attached to the outer SWNT of the DWNT, and various angular positions of the plate [177]. There is plenty of room, as well, for the application of few-walled carbon nanotubes in devices for energy harvesting/storage (solar cells, for example) and sensors [179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195][196][197]. Indeed, we currently feel that finally the synthesis methods have advanced significantly to be technologically useful for producing high quality materials that are appropriate for testing several CNT applications that have been proposed in the literature or have been poorly tested.…”