Gas field ion source with coated tip
Coated tips, as well as related articles, systems and methods are disclosed.
1. An article, comprising:
a first electrically conductive material having a surface; and
a coating supported by the first electrically conductive material,
wherein:
the article is configured to be used as a tip in a gas field ion source;
the coating is supported by the first electrically conductive material in a region of the article where, when the article is being used as the tip in the gas field ion source, an electric field of the article is insufficient to cause all ions generated by the article to accelerate away from the article without contacting the surface of the first electrically conductive material; and
the coating is supported by the first electrically conductive material only where, when the article is being used as the tip in the gas field ion source, an average emission current density from the article is at most 50% of a maximum emission current density from the article when the article is being used as the tip in the gas field ion source.
2. The article of claim 1 , wherein the coating is supported by the first electrically conductive material only where, when the article is being used as the tip in the gas field ion source, the average emission current density is at most 25% of the maximum emission current density from the article when the article is being used as the tip in the gas field ion source.
3. The article of claim 1 , wherein the maximum emission current density from the article when the article is being used as the tip in the gas field ion source is at most 1 pA/Å 2 .
4. The article of claim 1 , wherein the coating comprises a second electrically conductive material.
5. The article of claim 4 , wherein the second electrically conductive material comprises an electrically conductive material selected from the group consisting of metals, alloys and carbon.
6. The article of claim 1 , wherein the coating is supported by the first electrically conductive material only where an angle between a normal to the surface of the first electrically conductive material and an axis normal to an apex of the first electrically conductive material is least 15°.
7. The article of claim 6 , wherein the coating is supported by the first electrically conductive material except within a distance of 200 nm of an apex of the first electrically conductive material as measured along the surface of the first electrically conductive material.
8. A system, comprising:
the article of claim 7 ; and
an optical system configured so that, during use, when the article emits an ion beam, the optical system can direct the ion beam toward a surface of a sample.
9. The article of claim 1 , wherein the coating is supported by the first electrically conductive material except within a distance of 200 nm of an apex of the first electrically conductive material as measured along the surface of the first electrically conductive material.
10. The article of claim 1 , wherein the article has average full cone angle of from 15° to 45°.
11. The article of claim 1 , wherein the article has an average radius of curvature of 200 nm or less.
12. The article of claim 1 , wherein the first electrically conductive material comprises an electrically conductive material selected from the group consisting of metals, alloys, carbon, polymers and ceramics.
13. The article of claim 1 , wherein the first electrically conductive material comprises a material selected from the group consisting of tungsten, carbon, tantalum, iridium, rhenium, niobium, platinum and molybdenum.
14. The article of claim 1 , wherein the first electrically conductive material comprises W(111).
15. The article of claim 1 , wherein the first electrically conductive material has a terminal atomic shelf that is a trimer.
16. A system, comprising:
the article of claim 1 ; and
an optical system configured so that, during use, when the article emits an ion beam, the optical system can direct the ion beam toward a surface of a sample.
17. The article of claim 1 , wherein the first electrically conductive material has a terminal atomic shelf comprising 20 atoms or less.
18. An article, comprising:
a first electrically conductive material having a surface; and
a coating comprising a second electrically conductive material, the coating being supported by the first electrically conductive material,
wherein:
the article is configured to be used as a tip in a gas field ion source;
the coating is supported by the first electrically conductive material except within a distance of 200 nm of an apex of the first electrically conductive material as measured along the surface of the first electrically conductive material;
the coating is supported by the first electrically conductive material only where an angle between a normal to the surface of the first electrically conductive material and an axis normal to an apex of the first electrically conductive material is least 15°;
the coating is supported by the first electrically conductive material in a region of the article where, when the article is being used as the tip in the gas field ion source, an electric field of the article is insufficient to cause all ions generated by the article to accelerate away from the article without contacting the surface of the first electrically conductive material; and
the coating is supported by the first electrically conductive material only where an average emission current density from the article is at most 50% of a maximum emission current density from the article when the article is being used as the tip in the gas field ion source.
19. A system, comprising:
the article of claim 18 ; and
an optical system configured so that, during use, when the article emits an ion beam, the optical system can direct the ion beam toward a surface of a sample.
20. The article of claim 18 , wherein the coating is supported by the first electrically conductive material only where the average emission current density is at most 25% of the maximum emission current density from the article when the article is being used as the tip in the gas field ion source.
21. The article of claim 18 , wherein the first electrically conductive material comprises a material selected from the group consisting of gold, silver, palladium, osmium, tungsten, tantalum, iridium, rhenium, niobium, platinum and molybdenum, and wherein the second electrically conductive material comprises a material selected from the group consisting of gold, silver, palladium, osmium, tungsten, tantalum, iridium, rhenium, niobium, platinum and molybdenum.
22. The article of claim 18 , wherein the first electrically conductive material has a terminal atomic shelf comprising 20 atoms or less.