Substrate Topography Guides Pore Morphology Evolution in Nanoporous Gold Thin Films

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Nanoporous gold (np-Au) thin films exhibit unique properties relevant to catalysis and sensing.
• Controlling the morphology of np-Au films is crucial for optimizing their performance.
• Substrate topography is an underexplored factor in np-Au film evolution.

Purpose of the Study:

• To investigate the impact of substrate topography on the morphological evolution of nanoporous gold thin films.
• To identify the critical parameters governing np-Au film morphology on patterned substrates.
• To establish structure-property relationships based on substrate-induced morphological changes.

Main Methods:

• Fabrication of silicon ridges with varying widths (150 nm to 50 µm) and a height of 1 µm.
• Coating the patterned substrates with 500 nm-thick nanoporous gold films via dealloying of sputtered gold-silver alloy films.
• Analysis of film morphology using scanning electron microscopy (SEM) after dealloying and thermal annealing.

Main Results:

• Two distinct morphological evolution regimes were observed in the np-Au films.
• The ratio of the np-Au film thickness to the substrate ridge width was identified as the key determinant of these regimes.
• Specific morphological changes, such as dewetting or ridge-conforming growth, were linked to this ratio.

Conclusions:

• Substrate topography significantly influences the morphology of nanoporous gold thin films.
• The film thickness to ridge width ratio provides a predictive parameter for controlling np-Au film morphology on patterned surfaces.
• Understanding these topographical effects is essential for designing np-Au based devices with tailored properties.