In situ electrode manipulation for three terminal field emission characterization of individual carbon nanotubes

Abstract

In situ three terminal electron field emission characterization of an isolated multiwalled carbon nanotube has been performed, where both anode and gate electrodes are attached to high precision piezodrivers. All measurements are performed in a scanning electron microscope allowing accurate knowledge of the local environment of the nanotube to be obtained. It is shown that the presence of the grounded gate electrode screens the applied field by approximately 32%. This technique in positioning the gate and anode electrodes allows for an estimate of the gate transparency factor and demonstrates characterization of individual carbon nanotubes without the need for fabrication of arrays of emitters. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2335604͔Since the identification of carbon nanotubes ͑CNTs͒, 1 there has been sustained research into numerous potential applications of CNTs, in particular, for applications in field emission. 2,3 The high aspect ratio of a CNT results in a high local electric field for a given macroscopic field. As a result their use as electron sources for field emission based flat panel displays has been greatly explored, with the emergence of prototype displays. 4 While extensive two terminal field emission measurements have been performed, 2-6 considerably fewer three terminal studies 7-10 have been undertaken and those that have been performed have often been from arrays of nanotubes. In this letter we demonstrate a method of examining the gated field emission properties of an individual CNT and a method for establishing the gate transparency factor and the shielding of the emitter due to the presence of the gate itself. By performing the measurements in a scanning electron microscope ͑SEM͒ with electrodes attached to manipulators, we are able to investigate individual emitters, with a degree of freedom to move the electrodes in real time. Our approach opens the possibility of an effective method for testing the performance of a range of emitter structures prior to fabricating a prototype device, where the characteristics of an ensemble of emitters are measured. In addition, an ability to test single emitters may lead the way to enhance the emission uniformity from CNTs and increase the fraction of nanotubes that are actively emitting.Multiwalled carbon nanotubes were synthesized by a plasma arc discharge system between two graphite electrodes. The subsequent carbon deposit was purified by microfiltering and oxidization at 500°C to remove any amorphous carbon and carbon particulates, leaving purified CNTs. The CNTs were mixed into a polymer solution of polystyrene, which was dissolved in toluene. An ultrasonic treatment was used to improve the dispersion of the CNTs within the polymer. Vacuum casting methods were then used and the as-cast films were hot pressed to remove any residual solvent. To expose a single CNT the sample was mechanically broken and the broken edge studied in a Cambridge Instruments Stereoscan 250 III scanning electron microscope. A single CNT with a height ...

High-Performance Field Emission from a Carbonized Cork

“…The result shows that the electric field is highly focused at the top and edge of the graphitic sheets. Figure S2 reveals the dependence of the field-enhancement factor (β) on the distance between emitters as estimated from electrostatic calculations. − The field-enhancement factor indicates a degree of electric field enhancement due to the field emitter’s geometric effect. As shown in the figure, the field-enhancement effect diminishes rapidly because of the screening effect for distances between emitters less than 20 μm for the given height of 20 μm.…”

“…Various methods have been developed to form a graphene structure that is suitable for field emission such as direct growth, electrophoretic deposition (EPD), ion-mediated assembly, spin coating, screen printing, and transfer processes. − These methods, however, require a high-temperature chemical vapor deposition process, a complicated oxidation process to make the graphene oxide solution, or a cumbersome transfer process which makes fabrication very difficult. The graphene sheets in the graphene structure fabricated by these methods are usually randomly oriented, and the protruding graphene sheets cause a local concentration of the electric field, leading to excessive field emissions and eventually destruction due to Joule heating. , The presence of randomly oriented dense graphene sheets, on the other hand, decreases the electric field due to the screening effect, − resulting in an inefficient electric field distribution and hence imposing a limit on the field-emission enhancement.…”

Nanotip Contacts for Electric Transport and Field Emission Characterization of Ultrathin MoS2 Flakes

“…For a flat cathode, FE is enabled by a strong electric field (several kV/µm), while if the cathode surface has sharp edges or protrusions, electrons may be extracted by a considerably lower applied electric field, since the physical geometry provides a field enhancement near the emitting surface. To date, several nanostructures have been investigated as possible field emitters, like metallic nanowires and nanoparticles [26][27][28], semiconducting nanowires and nanoparticles [29][30][31][32][33], nanodiamonds [34], carbon nanostructures [35], carbon nanotubes (CNTs) [36][37][38][39][40][41], and graphene [33,[42][43][44]. Instead, few studies have investigated FE from MoS 2 structures, such as sheets and nanosheets [45,46], nanotubes and nanoflowers [47,48], nanostructures [49], thin films [50], and bilayers [12].…”

Space charge effects in field emission nanodevices

“…Reducing the operating voltage requires an increase in the emitter density of the FEAs as well as scaling of the gate aperture, emitter radius and work function of the emitter. For this purpose, many authors have been actively engaged in the preparation of advanced materials exhibiting lower work functions and miniaturized cathodes possessing smaller dimensions [4][5][6][7][9][10][11][12]. Recently, with the advent of new techniques in nanotechnology and nanofabrication, the aperture size has been scaled down to less than 100 nm.…”