1,079,342. Field emission cathodes; electron beam tubes. FIELD EMISSION CORPORATION. June 30, 1965 [Nov. 2, 1964], No. 27653/65. Heading H1D. A field emission cathode has a predetermined crystal lattice plane oriented at the surface of a sharpened portion of the cathode, and a layer of emissive material coated on the sharpened portion which migrates to, and concentrates at, the predetermined lattice plane upon heating, the coated portion having a lower work function than uncoated portions of the cathode so that elecelectron emission is limited substantially entirely to the predetermined lattice plane. A bonding material is also present in the layer to cause the emissive material to adhere better to the sharpened portion of the cathode. The sharpened portion may be a pointed tip or a knife edge on a heating filament, or on a rod heated by induction or electron bombardment to cause the migration of the emissive material. The cathode may be of W with a 100 or possibly 211 crystal lattice plane oriented at the tip, and the emissive material may be Zr, Hf, Mg, Cs, Ba or Th, which may be bonded to the W with an intermediate layer of O, N, Cl, I or F. Also, the cathode may be of Mo, Pt, Ni, Si or diamond. In particular, a W cathode 32 having a pointed tip is exposed first to O already present in a cathoderay tube or produced by decomposing copper oxide, and then to Zr by heating a Zr-coated filament 36 arranged within control grid 34. The tube is divided into two chambers by collimating electrode 42 which may be disc-sealed through the envelope, and the pressure in the gun chamber is maintained lower by gettering material 80 provided as shown, or between two plates which together form the collimating electrode, Fig. 3 (not shown). The oscilloscope tube shown further includes a magnetic focusing lens 52 with polepieces 54, or a corresponding electrostatic gun lens; a pair of beamblanking deflection plates 56; electrostatic focusing and deflecting electrodes 62-70; and a helical resistive coating 78 for post-deflection acceleration. The cathode may also be used in electron microscopes, charge-image storage tubes and electron beam machining apparatus.

The present invention provides a thin film for a reflection film or for a semi-transparent reflection film, which has at least one silver compound phase of nitride, oxide, complex oxide, nitroxide, carbide, sulfide, chloride, silicide, fluoride, boride, hydride, phosphide, selenide and telluride of silver, dispersed in a matrix formed of silver. The thin film according to the present invention keeps its reflectance without significant loss even after a long period of use, and can prolong the life of various devices which comprises the thin film as a reflection film, such as an optical recording medium and a display. The thin film can be also applied to a semi-reflective/semi-transparent film used in the optical recording medium.

A gas sensor is disclosed, which includes two separate metal electrodes on a surface of a substrate and a semiconductor thin film deposited on the surface of the substrate and connecting the two metal electrodes. The semiconductor thin film contains zinc oxide or a mixed oxide of zinc and indium, and the zinc oxide or the mixed oxide of zinc and indium are in the form of nanowires which constitute a gas-sensing surface of the semiconductor thin film. The nanowires have a diameter of 50-900 nm. The present invention also discloses a method for detecting the presence of a NOx gas.