Reliable Fabrication of High Aspect Ratio Plasmonic Nanostructures Based on Seedless Pulsed Electrodeposition

Abstract

shape, size, and periodicity. [21,22] For a variety of applications, it is desirable to increase the interaction volume of incident radiation within the nanostructures. [23] Recently, electrochemical deposition of metal through nanometric templates has attracted much interest due to its advantages over physical deposition, [19,[24][25][26][27] such as lower material cost, better film morphology, and higher aspect ratio. [27] Typical plasmonic metals in the UVvis-NIR regions are silver, gold, aluminum, and copper, [28][29][30] all of which except aluminum can be electrodeposited using aqueous solutions. For plasmonic applications in the visible range, silver has the lowest loss. However, gold, having slightly higher loss, especially below its interband transition at 539 nm, is often preferred due its inertness and biocompatibility. [29,31] It is for these reasons that gold is the metal of choice for biological and chemical sensing applications. In addition to intrinsic metal

Hybrid Transverse–Longitudinal Modes for High Figure‐of‐Merit Localized Plasmonic Refractometric Sensing in the Visible Spectrum

“…The differences in the spectral contrast and mode positions are likely due to the dispersive properties of the conductive ITO film, which exhibits free carrier loss in the near infrared. The resistance of the ITO film across for 1 × 1 cm 2 is measured to be 20 Ω, a sufficient resistance to ensure a satisfactory seedless electrodeposition process . Other factors also contribute to the differences, such as the rounding caused by e‐beam proximity effects and thickness nonuniformity of the electrodeposition process (particularly for the tall vSRRs).…”

“…The nanopatterning was carried out by electron‐beam lithography (EBL) on indium tin oxide (ITO)‐coated glass substrate, followed by sonicated cold development process for achieving sub‐15 nm resolution at lower exposure dose . Pulsed electrodeposition was used instead of physical evaporation to overcome the thickness limitation in the lift‐off transfer, in addition to improving the surface morphology of the gold film . The deposition rate for the seedless pulsed gold electrodeposition is presented in the Note S1, Supporting Information.…”

Interplays of Dipole and Charge‐Transfer‐Plasmon Modes in Capacitively and Conductively Coupled Dimer with High Aspect Ratio Nanogaps

“…Figure 1 presents some examples of the high aspect ratio dimer and its variants for investigating the CTP mode, which were fabricated via a combination of nanolithography and pulsed electrodeposition described in our previous work, [50,51] briefly summarized in the following. The nanopatterning was first carried out by electron beam lithography (EBL), followed by a sonicated cold development process.…”

Alternative approaches for enhancing plasmonic sensor performance

“…The differences in the spectral contrast and mode positions are likely due to the dispersive properties of the conductive ITO film, which exhibits free carrier loss in the near infrared. The resistance of the ITO film across for 1x1 cm 2 is measured to be 20 Ω, a sufficient resistance to ensure a satisfactory seedless electrodeposition process [133]. Other factors also contribute to the differences, such as the rounding caused by e-beam proximity effects and thickness non-uniformity of the electrodeposition process (particularly for the tall vSRRs).…”

“…Pulsed electrodeposition was used instead of physical evaporation to overcome the thickness limitation in the lift-off transfer, in addition to improving the surface morphology of the gold film. [131,133] Based on this technique, vSRRs were successfully fabricated with feature sizes such as width in the sub-30 nm range and height comparable to the resist thickness. An example of the fabricated vSRR in this work is shown in Fig.…”