GB1205129A - Photocathodes containing antimony and method of making the same - Google Patents

Abstract

1,205,129. Cathode materials and processing. RCA CORPORATION. 8 March, 1968 [10 March, 1967], No. 11517/68. Heading H1D. A photocathode comprises in successive layers on an insulating substrate 20, a layer of tin oxide 30, a layer of antimony oxide 34 and a photoemissive layer 32 including antimony which is preferably activated by an alkali metal. The tin oxide layer 30 may be 0À1 to 1À0 microns thick and formed by spraying a solution of tin oxide in alcohol on to a glass support 20 heated to 500‹ C., Fig. 4 (not shown). The antimony oxide layer 34 may be formed by evaporating antimony on to the tin oxide in a vacuum to 100 to 300 A thickness (or until light transmission drops to 50%) and then oxidizing by means of a glow discharge in oxygen at 0À1 to 1À0 torr, Fig. 5 (not shown). Preferably antimony oxide layer 34 is made up of two to five separately formed sublayers. A further non-oxidized coating of antimony is applied over layer 34 prior to incorporating the photocathode in a discharge device, e.g. the proximity focus type image tube shown in Fig. 1. The photocathode mounted in the tube spaced 100 mils. from phosphor screen 27 and secured to re-entrant ring 18 may be activated by successive depositions of potassium and caesium from generators 36. The spacing between re-entrant ring 18 and ring 16 which seals the two cylindrical ceramic envelope portions 12, 14 is made large enough to permit adequate migration of alkali metal from generator 36 into the interelectrode space and at the same time is small enough to protect the generators from the high field, e.g. 15,000 volts, existing between the electrodes.