We show field emission from excimer laser crystallized ͑ELC͒ hydrogenated amorphous silicon (a-Si:H) at current densities and threshold fields suitable for display applications. The laser crystallized a-Si:H gives rise to a densely packed and relative sharp surface morphology that gives emission currents of the order of 10 Ϫ5 A ͑current densitiesϷ0.04 A/cm 2 ͒ at threshold fields less than 15 V/m in a diode configuration, without the need for a forming process. With the progress in utilizing ELC in flat panel driver electronics, a fully integrated field emission display on a single glass substrate can now be envisaged.

Lateral growth crystallization of hydrogenated amorphous silicon with single and multiple pulse excitation using a Nd:YAG laser at a wavelength of 532 nm and a 3 ns pulse width at a repetition of 10 Hz is shown. With single pulse crystallization, large grain sizes of the order of 1 m were obtained with an energy density Ͼ400 mJ/cm 2 , and these have been studied using transmission electron microscopy ͑TEM͒ and atomic force microscopy. We show that, by using extremely short ͑3 ns͒ multiple pulse excitation of significantly lower powers ͑Ͻ150 mJ/cm 2 ͒, than that used to crystallize amorphous silicon with single pulse excitation, a uniform growth of crystalline grains is observed. TEM gives evidence for lateral grain growth with multiple pulse crystallization at low energies. We suggest that a ''super sequential lateral growth'' mechanism is occurring.

The holy-grail in terms of flat panel displays has been an inexpensive process for the production of large area 'hang on the wall' television that is based on an emissive technology. As such electron field emission displays, in principle, should be able to give high quality pictures, with good colour saturation, and, if suitable technologies for the production of the cathodes over large areas were to be made available, at low cost. This requires a process technology where temperatures must be maintained below 450 o C throughout the entire production cycle to be consistent with the softening temperature of display glass. In this paper we show three possible routes for nanoscale engineering of large area cathodes using low temperature processing that can be integrated into a display technology.The first process is based on carbon nanotube-polymer composites that can be screen printed over large areas and show electron field emission properties comparable with some of the best aligned nanotube arrays. The second process is based on the direct large area growth of carbon nanofibres directly on to substrates held at temperatures ranging from room temperature to 300 o C, thereby making it possible to use inexpensive substrates. The third process is based on the use of excimer laser processing of amorphous silicon for the production of lithography free large area three terminal nanocrystalline silicon substrates. Each route has its own advantages, and flexibility in terms of incorporation into an existing display technology. The harnessing of these synergies will be highlighted together, with the properties of the cathodes developed for the differing technologies.

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