| 摘要 |
A method of forming a two-electrode capacitor comprises oxidizing a surface film of a first electrode of Ta, Nb, Ti, Bi or Al forming a layer of insulating material on the oxidized surface to fill fissures or cracks formed therein during the oxidation process, and depositing a second electrode on the surface. The first electrode may be deposited on glass or ceramic. In one example a layer 12 of tantalum 4000 Angstroms thick is deposited on a glass plate 10 by cathode sputtering and anodized, except for an end contact 16, in an electrolyte comprising a 1% aqueous solution of ammonium borate. The voltage across the growing oxide layer is raised to and maintained at 100 volts for at least 20 minutes to form an oxide layer 1600 Angstroms thick. The layer is coated with aluminium by evaporation in a vacuum chamber so that aluminium fills any cracks in the layer, and the surface aluminium is removed by etching in aqueous potassium hydroxide. The surface is then anodized in a 1% aqueous solution of boric acid with the maximum forming voltage at 125 volts. Counter electrodes 18 and 20 are then deposited by evaporation or cathode sputtering. These electrodes may be of aluminium or tantalum. In another example the anodized tantalum surface is placed in an evaporation chamber to 10-4 to 10-5 mm. and aluminium is evaporated slowly on to the surface, e.g. over a period of about 2 minutes instead of the normal 15 seconds. The residual oxygen and water vapour causes partial oxidation of the aluminium as it condenses on the metal oxide layer, and the deposited layer of aluminium serves as a counter electrode. |
