Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.

The transient transmittance of plasmonic metasurfaces consisting of metal antennas over a semiconductor substrate was investigated, focusing on the role of carrier multiplication within the semiconductor through hot carrier generation by localized surface plasmons. Time-resolved far-infrared pump-probe spectroscopy monitored the dependence of the optical responses on the metasurface periodicity, the substrate temperature (ranging from 10 K to 300 K), and substrate dopant level (ranging from 2.9×10¹² to 3.3×10¹⁵ cm⁻³). The relative position of the excitation wavelength with respect to the plasmon resonance of the metasurface is crucial for the dynamic response. Transmittance changes up to 50% were achieved if the excitation was close to the plasmonic resonance. By decreasing the periodicity of the metasurface, the transmission minimum shifts towards shorter wavelengths. The periodicity also significantly affected the field enhancement of the metasurface, which plays a crucial role in the charge carriers' dynamics. Cooling the samples results in much larger transient transmission changes owing to the higher impact ionization rate, carrier multiplication factor, and longer diffusion length. A low initial substrate dopant concentration was found to be favorable for achieving a large transient response. The simulations from the developed diffusive impact ionization model validated all experimental results. These findings provide insight into the carrier dynamics and pave the way for developing electro-optical devices operating in the far-infrared spectral range.