IOP Groups
Field Emission Displays
26 June 2002
A half-day Meeting by the Vacuum Group
Abstracts of the two invited talks (followed by a summary by JIB Wilson, Chairman)
"Towards field emission devices based on carbon nanotubes"
Dr Jean-Marc Bonard
Institut de Physique des Nanostructures, Faculté des Sciences de Base
EPFL - Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Suisse
Discovered ten years ago, carbon nanotubes have emerged in the last few years as one of the most exciting topics in nanophysics. Industries are also getting more and more interested in this system, as nanotubes are considered to be serious candidates for various applications. Among these, field emission has emerged as one of the most promising. Carbon nanotubes are capable of emitting high currents at low fields and are purported to be ideal candidates for the next generation of field emission flat panel displays.
In this talk, I will on one hand outline the progress achieved so far in the realisation of field emission devices, in particular for flat panel displays and lighting elements. For the latter type of application, we have demonstrated a cylindrical field emission diode, where the cathode is a metallic wire on which multiwall carbon nanotubes are grown by CVD, and which shows excellent performances. This allowed us to realize a luminescent, mercury-free, tube, which could provide an interesting alternative to usual fluorescent tubes.
On the other hand, I will also address some key issues for the future development of such devices. It is becoming increasingly apparent that field emission is an extremely selective process, and that the growth of the emitters has to be carefully controlled in order to optimise the emission and to ensure reproducible characteristics. These facts call for a better understanding of the growth process and of the role of the catalyst, as well as for a careful study of the field emission properties of individual tubes. First steps in these directions will be presented.
"Towards printable FEDs as the standard for mass-market displays"
Adrian P Burden*
Printable Field Emitters Ltd, Atlas Centre, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
adrian.burden@pfe-ltd.com, tel: 01235 445969, fax: 01235 445960.
The first generation field emission displays (FEDs) from companies such as Candescent, Futaba, Motorola, and PixTech were based on microtips. These have proven that the FED concept is a viable and elegant solution to creating bright and efficient flat panel displays. However, cost-effectively scaling the process of making these microtips over the large areas suitable for hang-on-the-wall televisions has not yet been possible. Printable Field Emitters (PFE) has always highlighted this issue and extolled the virtues of printing at least the cold cathode structure. In doing so, PFE unlocks the potential to create FEDs suitable for mass-market television in the much-vaunted 20-40 inch screen diagonal range.
This presentation will discuss the recent technical progress at PFE in creating a 5.7 inch quarter-VGA FED. Ironically, this is a small display necessary to convince potential manufacturers that this approach will lead to the standard for bigger mass-market displays. The presentation will discuss the techniques used to characterise the emitter ink both in terms of its printing properties and its emission properties. Particular attention will be placed on how the emission properties of test samples (which are quicker, easier and more cost effective to produce) can be confidently reconciled with those of the emitter working in the conventional triode structure required for a display module.
Finally, progress with the low cost approaches of creating the majority of the triode structure using printing technology will be presented. These processing advantages will be the key to making large wall displays affordable for the general consumer.
*The presenting author acknowledges all of his colleagues at PFE.
Summary (a personal view by JIBW):
The talk on nanotubes reviewed their structure, catalytic growth, and patterned deposition. Field emission theory was introduced and some devices were introduced that use this phenomenon. The problems with obtaining homogeneous electron emission and a high emitter density were illustrated with experimental data. Attention was given to the alignment of nanotubes by an electric field, and the properties of individual tubes. A practical realisation was described, with pictures, of a multi-walled nanotube cathode for a discharge lamp that emitted bright light from a phosphor coating on a surrounding envelope. The nanotubes were deposited in situ and fully sealed-off lamps were shown to have an acceptable lifetime. Finally, nanotube growth and simultaneous monitoring of electron emission was described.
The following papers refer to this work:
Submitted papers
"Field emission of individual carbon nanotubes in the Scanning Electron Microscope", submitted to Phys. Rev. Lett. (2002).
"Watching carbon nanotubes grow", submitted to Appl. Phys. Lett. (2002).
"Following the growth of carbon nanotubes by field emission measurements during chemical vapor deposition", submitted to Phys. Rev. B (2002).
"A fully sealed luminescent tube based on carbon nanotube field emission", submitted to Microelectronic Journal (2002).
"Raman spectroscopy and field emission of patterned carbon nanotube films", submitted to J. Phys. Chem. B (2002).
The talk on printable cathode materials for field emission gave a review of display requirements (eg size and resolution) showing the slot that might be filled by field emission displays, competing for instance with cathode ray tubes and plasma panel displays. The matrix-addressing scheme was described, and some commercial examples of FEDs were compared. Problems lay in the production costs and yield of most of these FED technologies. The advantages of the PFE fabrication lay in the use of special heterogeneous “inks” which had particles of, for instance, graphite embedded in a matrix. These could be screen-printed to provide a dense array of electron emitters with a small switch-on voltage. Some more details of the manufacturing processes were described, leading towards a 5.7” QVGA mono-display. Videos were shown of demonstrator displays made in this way, and progress towards a commercial product for 2005 was outlined.
^ To the top ^