METHOD OF DOPING THE SURFACE OF A METAL-OXYGEN COMPOUND AND ARTICLE COMPRISING A METAL-OXYGEN COMPOUND THUS DOPED

摘要

1374333 Doping oxide semi-conductors; image pick-up tubes PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 3 March 1972 [6 March 1971] 9997/72 Headings H1K and H1D The invention concerns a process for doping the surface of a porous layer of lead monoxide, e.g. a target for a vidicon tube of which it is desired to adjust the spectral response, with an element which replaces oxygen in the lead monoxide by chemisorption of a reactive gas-containing the replacing element. The process comprises firstly adsorbing the reactive gas into the lead monoxide surface at a temperature below that at which the reactive gas decomposes and in a concentration less than that required to replace the oxygen atoms of all the surface molecules by the replacing element and then, in the absence of any further reactive gas, raising the temperature of the lead monoxide layer so that the adsorbed reactive gas decomposes releasing the replacing element, which then replaces the oxygen atoms of a proportion of the surface molecules, the replaced oxygen escaping as a gaseous compound. For vidicon tube target manufacture the lead monoxide layer is preferably polycrystalline with plateshaped crystallite aligned perpendicularly to the glass face plate of the tube which carries a tin oxide or indium oxide layer on which the lead monoxide is vapour deposited. Suitable reactive gases are hydrogen compounds of Cl, Br, I, F, S, Se or Te, and details of deposition and decomposition temperatures and of appropriate reactive gas concentrations are given for several specific embodiments. Reference is made to bombardment of the doped lead monoxide layer with oxygen ions. If it is desired to dope the lead monoxide surface with two oxygen-replacing elements; e.g. firstly Cl or Br and then S, Se or Te; it is not necessary to maintain the temperature of the layer so low during the adsorption process for the second dopant as would be the case if this dopant were used on its own. This enables Te to be used as a dopant, obtained from H 2 Te reactive gas, the temperature required when Te alone is used being so low that no appreciable vapour pressure occurs.