Patent ID: 8314403

Claim:
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.