# Self-Organized Conductive Gratings of Au Nanostripe Dimers Enable Tunable Plasmonic Activity
## 2 Results and Discussion
### Plasmonic and Conductive Nanostripe Arrays
The change of the nanoantennas' shape with an increase of the aspect ratio \(h\)/\(w\) from 0.21 to 0.28 induces a blue shift of the LSP from 615 nm (blue curve, \(h\) = 22 nm) to 560 nm (red curve, \(h\) = 30 nm). In parallel, a decrease of the full width half maximum of the plasmonic extinction is observed, despite equivalent underlying templates having been exploited in the two cases. Out of resonance, a strong amplification of the TM transmittance with respect to the TE intensity is detected, confirming that the nanostripe arrays behave as broadband wire grid polarizers from the near-UV to the IR spectral range. In particular, the NIR extinction ratio \(r\) = T\({}_{\text{TM}}\)/T\({}_{\text{TE}}\) of these Au nanostripes array reads about 4.8 at a 1096 nm wavelength, and even better performances are expected in the red-shifted part of the spectrum. Provided the high degree of order of the gratings, the detected plasmonic behavior is in full agreement with the optical response of corresponding 1D gratings calculated via finite element method simulations [31]. Figure 1:, (**a,b**) AFM topography and cross-section line profile of the nanopatterned glass template; (**c**) Picture of the sample: the plasmonic nanostructures homogeneously extend over large area (cm\({}^{2}\)); (**d,e**) sketch of the glancing angle Au evaporation growth on the wide and on the narrow facets, respectively; and (**f,g**) SEM images of the tilted Au nanostripe arrays grown under condition of panel (d,e), respectively. The red scale bars in panel (**f,g**) correspond to 500 nm and 1 μm, respectively. Alternatively, the optical response of these templates can be modulated by performing Au evaporation on the narrower facets (Figure 1e,g). Under this condition, the template imposes a reduction of the antennas' width in the range of 80 nm, with a possibility to finely tailor this parameter by changing the metal evaporation angle (\(\theta_{2}\)). The optical response of the quasi-1D array obtained for \(\theta_{2}\), respectively fixed at 50\({}^{\circ}\) (green curves) and 70\({}^{\circ}\) (black curves), is shown in Figure 2b for the near-UV, VIS and near-IR spectrum, and detected up to a 1800 nm wavelength. In analogy to the wider nanostripe samples, a narrow-band plasmonic resonance is detected under TM-polarized illumination (dashed curves), which blue-shifts from 620 nm to 540 nm wavelengths as a consequence of the increase of the aspect ratio (i.e., a decrease of \(w\)) under more grazing Au growth. Remarkably, a strong dichroism is detected in the near-IR spectral range, where the transparency exceeds the 90% for transversal polarization (TM), while is attenuated in the range of 20%-40% for TE polarization at about a 1600 nm wavelength. The latter behavior is due to the high reflectivity of the film along the non-resonant polarization, suggesting the possibility of achieving a macroscopic electrical transport parallel to the nanostripes' long axis. The possibility to combine high electrical conductivity with optical dichroism has been probed by measuring the longitudinal sheet resistance of the arrays, \(R_{s}\), as schematically shown in Figure 2c. The longitudinal sheet resistance (Figure 2d) has been measured over a macroscopic circuit of 5\(\times\)5 mm\({}^{2}\) size during Au growth in three different samples, where plasmonic nanostripes were confined on the  
Figure 2: (**a,b**) Optical extinction spectra of quasi-1D Au nanostripe arrays confined on the wide and on the narrow facets, respectively, as sketched in Figure 1d,e. The spectra were recorded for the longitudinal (TE-continuous lines) and transversal (TM-dashed lines) polarization of the UV-VIS-NIR illumination beam, with respect to the nanostripes’ long axis.