The electron beam induced deposition (EBID) permits highly precise fabrication of truly three-dimensional nanostructures of almost arbitrary shapes on any conductive substrate using metal-organic precursors. The EBID process makes use of the local decomposition of a typically metal-organic compounds as precursor gases (e.g. dimethyl-gold(III)-acetyl-acetonate) under the electron beam. A gas-injection system (GIS) inserts a precursor gas into the vacuum chamber of a scanning electron microscope (SEM), the precursor molecules which adsorb, desorb and diffuse at the substrate surface are locally decomposed by the electron beam. The structures that form during decomposition of the organo-metallic precursor gas contain a matrix of carbonaceous material in which single crystalline metallic nanocrystals of a few nanometers in diameter are dispersed. This implies that the EBID-material itself is a metamaterial. |
Since the metal content of this material is very low, several approaches are discussed how to overcome this drawback. The first one is to decrease the carbon content of the structure by electron beam irradiation with either ambient or locally injected water vapor. The splitting of water molecules by electron beam impact results in reactive oxygen species which oxidize the carbon of the EBID material creating volatile carbon oxides. Another approach is to use the EBID structure as a template and achieving the plasmonic response by a metallic coverage.
The optical response of chiral structures are under current investigations. A comparative study examines the scattered field by plan wave incident for pure EBID-structures, coated structures and those who are treated with water vapor.
caspar.haverkamp@mpl.mpg.de