Patent Number: 
Section: claims

1. A positive/negative phase shift bimetallic zone plate; comprising:a first metallic material having a positive phase shift;a second metallic material having a negative phase shift at a working energy point;wherein the first metallic material and the second metallic material are alternately arranged, so that the second metallic material replaces the blank portion in a cycle of a traditional zone plate. 2. The positive/negative phase shift bimetallic zone plate of claim 1, wherein the positive/negative phase shift bimetallic zone plate is annular, and the first metallic material and the second metallic material form a structure of alternate rings. 3. The positive/negative phase shift bimetallic zone plate of claim 1, the first metallic material is selected from nickel, gold, germanium, titanium, vanadium, chromium, manganese, iron, copper, zinc. 4. The positive/negative phase shift bimetallic zone plate of claim 1, the second metallic material is selected from titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, hafnium, tungsten, rhenium and osmium. 5. The positive/negative phase shift bimetallic zone plate of claim 1, wherein in the case that the positive/negative phase shift bimetallic zone plate has the same thickness as that of a normal monometallic phase zone plate, the diffraction efficiency of the positive/negative phase shift bimetallic zone plate is higher than the diffraction efficiency of the normal monometallic phase zone plate in conventional ranges. 6. The positive/negative phase shift bimetallic zone plate of claim 1, the positive/negative phase shift bimetallic zone plate is a vanadium-nickel, titanium-nickel, or vanadium-gold bimetallic zone plate. 7. A method of producing a positive/negative phase shift bimetallic zone plate, comprising following steps:a. depositing a thin film of a first metallic material on a substrate;b. forming a photoresist having a zone plate structure on the thin film of the first metallic material;c. transferring the zone plate structure to the thin film of the first metallic material by performing etching via the formed photoresist having the zone plate structure, so as to form a zone plate structure of the first metallic material;d. depositing the second metallic material at interspaces formed by the etching;e. removing the photoresist, so as to form a positive/negative phase shift bimetallic zone plate structure. 8. The method of claim 7, wherein the photoresist is coated by spin coating, and thereafter is subjected to electron beam exposureor interference lithography, so as to form a photoresist having a zone plate structure. 9. The method of claim 7, wherein the etching in step d is performed by argon ion etching or reactive ion etching. 10. The method of claim 7, further comprising:opening a window on the back side of the positive/negative phase shift bimetallic zone plate structure obtained in step e, to obtain the positive/negative phase shift bimetallic zone plate.