Focused Electron Beam Induced Deposition
Focused electron beam induced deposition (FEBID) is a direct-writing approach for the fabrication of 2D- and 3D-nanostructures.
Over the last decade FEBID or, more generally, focused electron beam induced processing (FEBIP) has developed from a rather exotic technique, employed by a small number of specialist groups for a rather limited but important selection of applications, such as mask repair, into a highly versatile technology for various materials research areas.
The basic principle of FEBID is simple. Provided by a gas injection system (GIS) or an environmental chamber inside of an electron microscope, a precursor gas adsorbed on a surface (see Fig.1) is dissociated in the focus of an electron beam. This brief description shows an apparent conceptual similarity to 3D-printing, in particular if one considers the 3D writing capabilities of FEBID.
A closer look, however, reveals the intrinsic complexity of the process. The electron-induced dissociation process is mostly triggered by low-energy electrons, i.e. the secondary electrons generated by the primary electrons SEI) and also by the backscattered electrons (SE II). For the process several dissociation channels are available with strongly energy-dependent and precursor-specific cross-sections. Which precursor to choose for a given application has to be carefully considered, as the growth process depends on several precursor-specific aspects, such as its vapor pressure at around room temperature, the adsorption characteristics of the precursor molecules and the stability of their stability under adsorption.
One unique advantage of FEBID, as compared to other direct-writing techniques, is its 3D fabrication capability, as is shown exemplarily in Fig.2. In this example a heteronuclear precursor containing Fe and Co has been used (HFeCo3(CO)12). The nano-cubes are ferromagnetic and show highly complex magnetic hysteresis loops.