A focused electron beam can directly deposit complex features onto a substrate in a single step. While this is an established technique for gold, platinum, copper and further metals, direct electron beam writing was not previously possible for silver, which the researchers believe has limited its use in nano-optics applications in information technology.
According to the team, typical silver compounds are difficult to evaporate and are highly reactive. During the heating in the injection unit, they tend to chemically react with the reservoir walls and if there is a drop in temperature during their journey from the reservoir to the tip of the needle, the compounds freeze and obstruct the tube.
"It took us a lot of time and effort to design a new injection unit and find a suitable silver compound," explains HZB physicist Dr Katja Höflich. "The compound silver dimethylbutyrate remains stable and dissociates only in the focus of the electron beam."
Information about the composition of the silver nanostructures’ surfaces can be obtained from the colour and intensity of scattered light, which could be used to detect the fingerprint of specific molecules that bind to the silver surface. The nanostructures could therefore be good candidates as sensors for explosives or other dangerous compounds.
The team believes complex silver nanostructures could also one day constitute the basis for purely optical information processing.
