Figure 11.

FEBID/ focused ion beam (FIB) assisted, photonic/plasmonic tip-enhanced Raman scattering (TERS) nano-probe. (a) Overview of a 100 nm thick Si₃N₄ AFM cantilever, equipped with the photonic and plasmonic element, based on FIB and FEBID, respectively. (b) shows a close up in which the FIB holes (160 nm diameter and 250 nm distance) are evident. The central element uses a Pt-based 3D-FEBID pillar as scaffold, further coated with pure Ag and milled down via FIB to apex radii of 5 nm and below (c). Such TERS nano-probes are then used in AFM-based configuration, as shown in (d), where the laser couples in from the backside via the photonic element, launching surface plasmons. After propagation along the cone structures, they induce a localized plasmon resonance at the tip apex in a nanometer-sized volume. (e) shows an AFM height image in 3D representation of a sub-micrometer Si nanocrystal/SiO_x trench. The Raman intensity along the red line is shown in (f) in a spectrally resolved diagram, where the intensity variation reflects the crystallinity degree. As evident, the applied step size of 7 nm allows for sharp intensity edges, which confirms a sub-10 nm resolution in TERS operation. Adapted and reprinted from De Angelis et al., Nat. Nanotechnol. 2010 [128].