Expanded Design Flexibility in 3D-Nanoprinting via Focused Electron Beam Induced Deposition

While the miniaturization trend in research and industry is still unbroken, there is a rising demandon fabrication technologies, which allow fabrication of 3-dimensional architectures with graduallydecreasing dimensions. Among a small pool of technologies, which enable 3D fabrication at thenanoscale, Focused Electron Beam Induced Deposition (FEBID) is a highly promising candidatedue to both, its capabilities and increasing reliability [1]. Based on the working principle, whichrelies on the beam induced dissociation of surface adsorbed, gaseous precursor molecules,FEBID has very low demands on substrate materials and morphologies. Together with its additivecharacter and a constantly increasing precursor material pool, FEBID reached the status of a3D-nanoprinter for a wide range of novel applications, including 3D sensors, plasmonics,-nanomagnetics or SPM nanoprobes. Most 3D designs in the past were of mesh-like character bymeans of nanowires connected in 3D space (Fig 1). While desired for many applications, the smallnanowire dimensions can entail limitations to relevant properties. Consequently, that expansion ofdesign possibilities is of high relevance, which includes fully closed structures, sheet-like elementsor their combination with the mesh-like architectures (Fig 2).Following that motivation, this contribution focuses on two different approaches: (1) controlleddiameter tuning of individual nanowires and (2) fabrication of closed, sheet-like elements. Theformer strategy uses the introduction of a deliberate beam defocus, which has manifoldimplications during growth aside of the originally intended diameter widening [2]. We discuss thoseresults from a practical point of view and demonstrate the enhanced design flexibility of varying oreven dynamically changing nanowire-dimensions. The second approach forms the baseline for 3Dnanoprinting of objects, composed of sheet-like base-elements. Here, we discuss the basicimplications when changing from nanowires to quasi-2D sheets, based on the more complexthermal situation. We present an unified compensation model, taking those effects into account,leading to very high precision [3]. Both together consequently form the basis for enhanced designflexibility of 3D-FEBID, which is stepwise leveraged into the status of a true 3D nanoprinter for yetunknown applications in 3D space.