New Stamping Process Creates High-Resolution Metallic Nanopatterns in a Single Step

A new single-step process was used to print the letters and shapes on a piece of silver film that is only a quarter as wide as a human hair.

The researchers--graduate student Keng H. Hsu, assistant professor Nicholas X. Fang, professor Placid M. Ferreira and graduate student Peter L. Schultz--shared the details in a paper that appeared in the February 14 issue of the journal Nano Letters, one of the most authoritative journals for nanotechnologists.

The groundbreaking process they described in their paper uses a patterned superionic material as a stamp; patterns are etched onto metallic film via an electrochemical reaction. The advance creates high-resolution metallic nanopatterns in a single step, which could potentially reduce manufacturing costs and increase yields. (Conventional processing involves multiple steps in which patterns are first placed on a photoresist, followed by metal deposition and subsequent etching.)

The new single-step process was used to print the letters and shapes in the above image on a piece of silver film that is only a quarter as wide as a human hair. To make such patterns, the researchers use focused ion beam milling to carve patterns into a stamp made of superionic material, such as silver sulfide. The stamp is then placed on a substrate, and a voltage is applied. This produces an electrochemical reaction at the contact points of the interface. The reaction generates metal ions, which migrate across the interface into the stamp. The stamp acts like a sponge, soaking up metal ions. As the reaction continues, the stamp progresses into the substrate, which generates features complementary to the pattern on the stamp.