LAUSR

DOI: 10.1002/adom.202000879 plasmonic structures, they struggle as soon as complex arrangements of different nanoparticles are needed, possibly even distributed on large areas as well as in periodic arrangements. Only recently, with the advent of sophisticated DNA-guided nanotechnology, also in combination with other techniques, it became possible to create such structures.[8–11] In contrast, top-down techniques such as optical lithography and electron-beam lithography straightforwardly offer the required periodic and well defined arrangement on surfaces. Taking these techniques a step further, they are also able to realize 3D arrangements by virtue of mark recognition and layered fabrication.[12] Additionally, these top down techniques allow for a larger variety of structures and can be used to fabricate solid particles of almost any metal or dielectric as well as inverse structures, such as slits and holes in metallic and dielectric films employing Babinet’s principle.[13] Electron-beam lithography (EBL) has been utilized for many years and is a prime candidate for highest resolution structuring and layered processes. Using positive and negative tone resists, lift-off, reactive and nonreactive ion (beam) etching, a plethora of solid and inverse structures can be fabricated.[14,15] The technique, however, faces a few limitations: The fabrication of “sculptured” structures, that is, of structures with varying thickness or shape or of particles with complex 3D shapes, is extremely difficult if not impossible. While EBL gray-scale lithography can be applied in some cases, this technique is intrinsically process-instable and difficult to control. Another limitation lies with the EBL resists as not all samples or structures tolerate resists, either due to contamination issues, due to the fragility of the substrate, for example, in case of transmission electron microscopy (TEM) membranes, or due to very small sample sizes which do not allow for homogeneous resist spin coating. In some of these cases the use of a focused ion-beam (FIB) tool has proven successful.[16,17] Here, a beam of focused ions sputters and allows to structure the material of interest directly.[18–21] The main use of these so-called cross beam tools, consisting of a (crossed) scanning electron column and a focused ion beam column, lies with the fabrication of TEM cuts and lamellas for material inspection. Consequently, the resolution of these tools is limited in two aspects: For so-called FIB cuts as well as TEM lamella production large amounts of material have to be removed which Plasmonics is a field uniquely driven by advances in microand nanofabrication. Many design ideas pose significant challenges in their experimental realization and test the limits of modern fabrication techniques. Here, the combination of electron-beam and gold ion-beam lithography is introduced as an alternative and highly versatile route for the fabrication of complex and high fidelity plasmonic nanostructures. The capability of this strategy is demonstrated on a selection of planar as well as 3D nanostructures. Large area and extremely accurate structures are presented with little to no defects and errors. These structures exhibit exceptional quality in shape fidelity and alignment precision. The combination of the two techniques makes full use of their complementary capabilities for the realization of complex plasmonic structures with superior optical properties and functionalities as well as ultra-distinct spectral features which will find wide application in plasmonics, nanooptics, metasurfaces, plasmonic sensing, and similar areas.