Screen-printed Carbon Nanotube Films Research Articles

A comparative study of field emission properties of carbon nanotube films prepared by vacuum filtration and screen-printing

A comprehensive comparative study of electron field emission properties of carbon nanotube (CNT) films prepared by vacuum filtration and screen-printing was carried out. Field emission performance of vacuum filtered CNT films with different filtered CNT suspension volumes was systematically studied, and the optimum electron emission was obtained with a low turn on field of ∼0.93 V/μm (at 1 μA/cm 2) and a high field enhancement factor β of ∼9720. Comparing with screen-printed CNT films, vacuum filtered CNT films showed better electron emission performance, longer lifetime, and greater adhesive strength to substrates. This work reveals a potential use of vacuum filtered CNT films as field emission cathodes.

The influence of organophilic clay on field electron emission uniformity and lifetime of screen printed carbon nanotube film

The effect of adding clay, modified by a silane coupling agent, into the carbon nanotube (CNT) paste on the field electron emission and a lifetime of screen printed CNT film was studied. The composition of organophilic clay and CNTs was characterized by a combination of X-ray diffraction, and scanning electron microscopy. The incorporation of clay improved the dispersivity, adhesiveness, and conductive networking of paste, therewith enhancing the field emission's uniformity and stability. The improvement of this gas barrier on the CNT film by clay loading prevents emission degradation.

Ar, O 2, CHF 3, and SF 6 plasma treatments of screen-printed carbon nanotube films for electrode applications

This paper investigates the consequence of the material property and the plasma gas chemistry (herein referred to the plasma gas-feeding species and methods) on the electrode performance in plasma treatments of screen-printed carbon nanotube (CNT) films. Four plasma gases (Ar, O 2, SF 6, and CHF 3) and three gas-feeding methods were examined. The surface morphology, microstructure, and composition of 11 sample groups have been carefully characterized. Tests of the CNT film electrode subjected to gas discharge and field emission show that surface morphology modification is the most influential factor in respect of lowering the onset voltages. In detail, O 2/Ar (O 2 followed by Ar) and Ar + CHF 3 + SF 6 (mixed three gases) treatments are the best choices for ionization and field emission applications, respectively. The relevant results are even better than that of the samples of aligned CNT films prepared by chemical vapor deposition. The underlying mechanisms are modeled by two opposing processes (etching and coating), which phenomenally produce three competing effects, i.e., CNT protruding, bundle forming, and neo-nanostructure forming. The results and the correct behavior of our model suggest that the plasma gas chemistry is the most fundamental factor in the process of plasma treatments of CNT films.

Low-temperature synthesis of one-dimensional ZnO nanostructures on screen-printed carbon nanotube films

One-dimensional (1D) ZnO nanostructures including nanowires, nanobelts, and nanorods were synthesized on screen-printed multi-walled carbon nanotube (MW-CNT) films in a thermal chemical vapor deposition process by gold (Au) nanoparticle-catalyst and self-catalyst driving at low temperatures of 400 and 500 °C. ZnO nanowires and nanobelts by introducing Au nanoparticles were grown via the vapor–liquid–solid (VLS) mechanism, while ZnO nanorods were realized via a self-catalytic VLS process. It was found that the diameter of ZnO nanowires strongly depends on that of Au nanoparticles, indicating the typical metal catalyst-driving VLS process. On the other hand, ZnO nanorods without Au-alloyed tips are comprised of hexagonal facets, suggesting self-catalytic VLS formation of the ZnO nanorods on the MW-CNT films. Room temperature photoluminescence spectra of the 1D ZnO nanostructures exhibit an ultraviolet emission band around 378 nm and deep-level emission band centered around 505 nm.

Effect of Electrical Aging on Field Electron Emission from Screen-Printed Carbon Nanotube Film

We investigated the effect of electrical aging on field electron emission from a screen-printed carbon nanotube (CNT) film. After maintaining the field-emission current density at 20 mA/cm2 for 3 h in the DC mode, it was observed that initially long CNTs became short and initially lying CNTs stood up. As a result, the field-emission uniformity and lifetime were markedly improved. From the analysis of the corresponding Fowler–Nordheim plots using a temperature-dependent formula, the shortening of CNTs by electrical aging was found to originate from the thermal evaporation of carbon atoms at the tip of CNTs during field electron emission.

Effects of plasma treatment on microstructure and electron field emission properties of screen-printed carbon nanotube films

The effect of H2, N2 and NH3 plasma treatment on the microstructure and field emission (FE) properties of the screen-printed carbon nanotube (CNT) films has been systematically examined. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy were used to characterize the microstructural changes of the CNTs. The results indicated that the surface of CNTs became rough, and on which a lot of nano-protuberances appeared after plasma treatment. FE experiments showed the treated CNT films had superior FE behavior with emission site density (ESD) dramatically increasing from 103 to 106/cm2. The mechanism of ESD enhancement and variation of FE properties with treatment time have been discussed.

Enhanced surface morphologies of screen-printed carbon nanotube films by heat treatment and their field-emission properties

A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications.

Improvement of Field-Emission Properties of Screen Printed Carbon Nanotube Films via Argon Plasma Treatment

In this paper, we describe an effective surface treatment to improve the field emission site density. The carbon nanotube (CNT) films fabricated by a screen printing process have been exposed to Ar plasma for varying durations and their field emission characteristics have been measured. The CNT films, after applying an Ar plasma treatment, have excellent field emission characteristics with very high emission current and low threshold fields. Scanning electron microscopy showed the contamination removal from the surface of the CNT films, and transmission electron microscopy showed the structural modification of the CNT walls after exposure to Ar plasma. Raman results showed that the particles generated by the deformation of the CNT structure had characteristics of both single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs). We attribute improvement of field emission properties to the changes of the geometrical structure of the local emission region in MWCNTs.

Significant improvement of field emission by depositing zinc oxide nanostructures on screen-printed carbon nanotube films

In order to improve the field emission properties of screen-printed carbon nanotube films, ZnO nanostructures were deposited on multiwall carbon nanotubes (MWNTs) using vapor phase transport method. Based on the combined effect of geometrical structure of MWNT/ZnO, a low turn-on field of ∼0.7V∕μm at current density of 0.1μA∕cm2, a low threshold field of ∼2.3V∕μm at current density of 1mA∕cm2, a high field enhancement factor of 8.2×103, and a homogeneous emission image with emission spot density of ∼105cm−2 were obtained from ZnO nanomultipods grown on MNWT film.

Field-emission enhancement from change of printed carbon nanotube morphology by an elastomer

The surface morphology of screen-printed carbon nanotube films was modified by using the poly-dimethylsiloxane (PDMS) elastomer. The entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. In addition, the cathode film morphology of top-gated triode structures can be treated by using the proposed surface treatment technique, which is a low-cost process.

P-118: Field Emission Improvement by Liquid Elastomer Modification of Screen-Printed CNT Film Morphology

The film morphology of screen-printed carbon nanotube emitters was modified by using the liquid elastomer. The entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. In addition, the modification of the cathode film morphology of top-gated triode type structures can be easily solved by using our based surface treatment technique, which is a low-cost, simple process. This technique has showed good possibility for surface treatment of large-size field emission displays (FEDs) in the future.

P‐33: Effect of Surface Treatments on Screen‐Printed Carbon‐Nanotube Films by Argon Plasma

AbstractWe have investigated effects of post‐treatment of carbon nanotubes(CNTs) films on field emission characteristics. CNTs films were prepared with Ar plasma treatment of different exposure times. With the Ar plasma treatment, electron emission at low threshold field was observed and higher emission current at 2.9 V/μm was generated, compared to the untreated films. Also the field emission site density of CNTs films was improved by Ar plasma treatment. We show that electrons can be emitted from not only CNT tip but also irradiation‐induced defects on CNTs walls.

Effect of ion impinging on the microstructure and field emission of carbon nanotubes

Effects of ion impinging on the microstructure and field electron emission properties of screen-printed carbon nanotube films were investigated. We observed that the plasma treatment modified the microstructure of CNTs along with the remarkable increase of emission site density. With the prolongation of ion impinging time, the emission current falls down first, and then rises up to higher than that of the untreated films. It is proposed that the change of emission characteristics is due to the different emission mechanisms. After the treatment, electrons are emitted predominantly from the nano-nodes on the tube wall instead from the nanotube tips.