Smiths Group Plc

Other

Smiths Industries Public Limited Company

Wang Nang Wang

Neil Anthony Fox

An electron emitter, such as for a display, has a substrate and regions of n-type material and p-type material on the substrate arranged such that there is an interface junction between the regions exposed directly to vacuum for the liberation of electrons. The p-type region may be a thin layer on top of the n-type region or the two regions may be layers on adjacent parts of the substrate with adjacent edges forming the interface junction. Alternatively, there many be multiple interface junctions formed by p-type particles or by both p-type and n-type particles. The particles may be deposited on the substrate by an ink-jet printing technique. The p-type material is preferably diamond, which may be activated to exhibit negative electron affinity.

Electron-emitting devices

Parallel cathode electrodes extend across the base plate of a display. Each electrode has teeth projecting from both sides, the teeth of adjacent electrodes being closely spaced from one another by a gap that is bridged by a dot of an electron emitter material. A glass screen spaced by a vacuum gap above the base plate carries transparent anode stripes extending transversely of the cathode electrodes and a fluorescent layer of colored phosphors on the anode stripes. A voltage applied between adjacent cathode electrodes and gates conduction via each electron emitter dot. A voltage applied to an anode stripe causes a part of the current from the emitter directly below the stripe to be directed towards the anode, thereby illuminating the phosphor pixel above the emitter.

Field-emission display

A diamond grit surface is formed on a substrate (,) having a metal surface (,), such as nickel, by applying a paste (,) of low-grade diamond grit in a binder to the surface. After driving off the binder, the diamond coated surface is placed in a reactor chamber (,) having a microwave plasma reactor (,) and connected to a hydrogen gas pump (,). The substrate (,) is heated in the hydrogen atmosphere at a reduced pressure. The metal surface (,) acts as a catalyst in the presence of the hydrogen plasma to cause regrowth of the diamond (,), giving an improved size, shape and adhesion. The method may be used to make diamond surfaces in electron emitter devices, circuit boards or abrasive devices.

Diamond surfaces

An electron emitter (2) has a semiconductor substrate (20) doped with an n-type region (21). A diamond layer (24) is doped by ion implantation with a p-type dopant to form a graded dopant profile region (27) that increases away from the upper surface of the diamond layer (24) and a thin insulating region (28) separating the p-type region (27) from the n-type region (21). The emitter (2) has a first electrical contact (23) on a lower surface of the substrate (20) and a second electrical contact (25) on the upper surface of the diamond layer (24) such that a voltage can be applied across the emitter (2) to cause tunneling of electrons from the n-type region (21) through the insulating region (28) into the p-type region (27), causing emission of electrons from an exposed surface (29). A lamp or display (1) includes several such electron emitters (2) and contains gas at reduced pressure, which is ionized by the emitted electrons, thereby generating UV radiation, which causes a fluorescent layer (5) on a transparent window (3) to produce visible light.

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Limpley Stoke, United Kingdom

Wang Nang Wang