Abstract: Graphite comprises atoms arranged in discrete layers (100). The perpendicular distance between these layers is the ‘d-spacing’ (101). A field emission material is obtained by expanding the d-spacing (102). Such expansion may be achieved by an intercalant that has been introduced between layers of the material. Such an intercalant may reside, or may no longer reside, in the material. The material may be placed in position on a substrate by a printing process, prior to expansion. Such field emission material may be used in cold cathodes in field electron emission devices.

Abstract: A field electron emission material is created by applying a silica precursor to graphite particles (11); processing the silica precursor to produce amorphous silica (12) which is doped and/or is heavily defective, and disposing the graphite particles (11) upon an electrically conductive surface (14) of a substrate (13) such that they are at least partially coated with the amorphous silica (12).

Abstract: A masking layer (405) is provided on selected areas of an electrode structure that is at least partly performed, to define masked areas and unmasked areas (emitter cells 410). A first constituent with particles (408) and a second constituent (409) are then applied to the emitter cells (410), and the particles (408) are selectively directed towards the bottoms of the emitter cells (410)—e.g. by electrophoresis. The masking layer (405) is then removed from the masked areas, together with any stray quantities of the first and second constituents (408, 409) on the masking layer (405). The first and second constituents (408, 409) are then processed (e.g. by curing) to create broad area field electron emission sites in desired locations of the electrode structure.

Abstract: A field electron emission cathode is manufactured by depositing on an insulating substrate 300, by low resolution means, a sequence of a first conducting layer 301, a field emitting layer 302 and a second conducting layer 303 to form at least one cathode electrode. There is then deposited on the cathode electrode by low resolution means, a sequence of an insulating layer 304 and a third conducting layer 305, to form at least one gate electrode. The structure thus formed is then coated with a photoresist layer 306. The photoresist layer 306 is then exposed by high resolution means to form at least one group of emitting cells, the or each such group being located in an area of overlap between a cathode electrode and gate electrode. To complete the cells, the conducting and insulating layers 305, 304, 303 are etched sequentially to expose the field emitting layer 302 in the cells, and remaining areas of the photoresist layer 306 are removed.

Abstract: A field electron emission material is formed by coating a substrate (221, 230) having an electrically conductive surface with a plurality of electrically conductive particles (223, 231). Each particle has a layer of electrically insulating material (222, 232) disposed either in a first location between the conductive surface of the substrate (221) and the particle (223), or in a second location between the particle (231) and the environment (237) in which the field electron emission material is disposed, but not in both of such first and second locations, so that at least some of the particles (223, 231) form electron emission sites at such first or second locations. A number of field emission devices are disclosed, utilizing such electron emission material.

Abstract: A field electron emission material has a substrate with an electrically conductive surface. Electron emission sites on the conductive surface each include a layer of electrically insulating material to define a primary interface region between the conductive surface and the insulating layer, and a secondary interface region between the insulating layer and the vacuum environment,. Each primary interface region is treated or created so as to enhance the probability of electron injection form the conductive surface into the insulating layer. Each primary interface region after such treatment or creation is either an insulator or graded from conducting adjacent the conductive surface to insulating adjacent the insulating layer.

Abstract: A field electron emission material comprises an electrically conductive substrate and, disposed thereon, electrically conductive particles embedded in, formed in, or coated by a layer of inorganic electrically insulating material. A first thickness material is defined between the particle and the environment in which the material is disposed. The dimension of each particle between the first and second thicknesses is significantly greater than each thickness. Upon application of a sufficient electric field, each thickness provides a conducting channel, to afford electron emission from the particles By use of an inorganic insulating material, surprisingly good stability and performance have been obtained. The particles can be relatively small, such that the electron emitting material can be applied to the substrate quite cheaply by a variety of methods, including printing. The material can be used in a variety of devices, including display and illuminating devices.