Field emission properties of carbon nanotube pillar arrays

Abstract

Carbon nanotube pillar arrays (CPAs) for cold field emission applications were grown directly on polished 70∕30at.% NiCr alloy surfaces patterned by photolithography. A carbon nanotube (CNT) pillar is a localized, vertically aligned, and well-ordered group of multiwalled CNTs resulting from van der Waals forces within high-density CNT growth. The edge effect, in which the applied electric field is enhanced along the edge of each pillar, is primarily responsible for the excellent emission properties of CPAs. We achieved efficient emission with turn-on fields as low as 0.9V∕μm and stable current densities as high as 10mA∕cm2 at an applied macroscopic field of 5.7V∕μm. We investigated the effects of pillar aspect ratio, density, and spacing on CPA field emission and quantified the edge effect with respect to pillar aspect ratio through modeling. We also investigated the field emission stability and found substantial improvement with CPAs compared to continuous and patterned CNT films.

Carbon Nanotube Field Emission Devices with Integrated Gate for High Current Applications

“…In the first case, the cathode structure is opposed by a planar anode, a diode configuration. The increase in electric field at the edge of the pillar has been associated with the performance improvement observed for CPAs when compared to other CNT structures [5,6].…”

“…The Kanthal substrate is then patterned by a photolithography process and subsequently coated with a 10 nm layer of Chromium and a 15 nm layer of Molybdenum film in order to inhibit CNT growth in the coated areas. The growth of the CPA is carried out by thermal chemical vapor deposition (CVD) at 750ºC with 200 SCCM Hydrogen and 800 SCCM Ethylene flowing into the growth chamber [6]. Fig.…”

“…Due to the relatively simple fabrication process and high reproducibility of CPAs, we are able to utilize these structures for the integration of the gate electrode. CPAs can be grown from patterned catalysts on substrates like Si or directly on bulk metallic alloy substrates that have been patterned with metal film layers that inhibit CNT growth [5,6]. Both of these fabrication methods yield CNT emitter structures that exhibit low turn-on fields and also excellent structural stability.…”

Enhanced field emission properties from carbon nanotube emitters grown on NiCr alloy surfaces with grain boundary effect

“…We reported previously on the field emission properties of MWNT films grown as pillars with 50 μm diameter based on a micropatterning technique [4]. Figure 1a shows the I-V curves for MWNT films grown on 80/20 and 70/30 NiCr alloys, which exhibit very distinct turn-on fields of 1.3 V/μm and 3.6 V/μm, respectively.…”

Gated carbon nanotube pillar arrays for high current applications

“…SEM images of a CNT pillar array (CPA) fabricated in our lab is shown in Fig 2a. The CNT pillar structures, shown in Fig 2b, may be fabricated by patterning metal catalysts or by directly growing the CNTs on patterned metal alloy substrate [2]. Through the use of conventional photolithography, CNT arrays with varying pillar diameters and inter-pillar spacing may be fabricated, depending on applications and the desirable emission current.…”