Patent GB-848755-A (GB)
Title: Improvements in or relating to methods of manufacturing unidirectional conducting elements
IPC: B01D47/06
Filed: 1956-12-31
Abstract: A unidirectional conducting element is made by cathodic bombardment of a metallic surface to transfer metallic particles on to a conducting base - plate, with simultaneous reaction with the gaseous atmosphere present to convert the metal into a compound having the desired semi-conductive properties; the receiving base-plate is heated (e.g. by induction) so that a mono-crystalline layer of semiconductor is deposited progressively.  The deposited layer may be cadmium, lead, thallium or antimony sulphide having photo-conductive properties, or may be a copper sulphide or oxide rectifying layer; the gases used are hydrogen sulphide and oxygen respectively.  The process may be carried out by making the metallic surface the cathode in a discharge device containing the required reactive gas at a low pressure.  The metal may first be evaporated on to an intermediate base plate which is inert to the metal (e.g. magnesium or aluminium) and this plate used as the cathode for transfer of the metal as above.  By this means impurities are held back and do not contaminate the final product.  The receiving base plate may be iron, aluminium or an aluminium-alloy; it may also be magnesium when a sulphide is formed, or copper for copper oxide.  When transfer is complete the vessel is evacuated and a further layer deposited on the surface to form a counterelectrode.  For photo-cells this can be a translucent film of aluminium or silver, but in the case of rectifiers a thicker film can be formed, of silver for copper sulphide or indium for copper oxide. The complete assembly is then cut up into smaller parts for use. A mixture of metallic sulphides may be formed by forming an alloy of the appropriate metals on the intermediate plate.  An activator may similarly be evaporated on this plate at the same time; this can be magnesium, silver or antimony.ALSO:A unidirectional conducting element is made by cathodic bombardment of a metallic surface to transfer metallic particles on to a conducting base-plate, with simultaneous reaction with the gaseous atmosphere present to convert the metal into a compound having the desired semi-conductive properties; the receiving base-plate is heated (e.g. by induction) so that a mono-crystalline layer of semi-conductor is deposited progressively.  The process may be carried out by making the metallic surface the cathode in a discharge device containing the required reactive gas at a low pressure.  The deposited layer may be cadmium, lead, thallium or antimony sulphide having photo-conductive properties, or may be a copper sulphide or oxide rectifying layer; the gases used are hydrogen sulphide and oxygen respectively.  The metal may first be evaporated on to an intermediate base plate which is inert to the metal (e.g. magnesium or aluminium) and this plate used as the cathode for transfer of the metal as above.  By this means impurities are held back and do not contaminate the final product.  The receiving base plate may be iron, aluminium or an aluminium-alloy; it may also be magnesium when a sulphide is formed, or copper for copper oxide.  When transfer is complete the vessel is evacuated and a further layer deposited on the surface to form a counter-electrode.  For photo-cells this can be a translucent film of aluminium or silver, but in the case of rectifiers a thicker film can be formed, of silver for copper sulphide or indium for copper oxide. The complete assembly is then cut up into smaller parts for use.  A mixture of metallic sulphides may be formed by forming an alloy of the appropriate metals on the intermediate plate.  An activator may similarly be evaporated on this plate at the same time; this can be magnesium, silver or antimony.