Strong Substrate Binding Modulates the Acoustic Quality Factors in Gold Nanodisks

Lithographically prepared plasmonic nanoparticles are ideal mechanical probes, as their vibrational behavior can be precisely tuned through particle size and shape. But these particles exhibit strong intrinsic and extrinsic damping that results in small vibrational quality (Q) factors. Here, we perform single-particle transient transmission microscopy to investigate the effect of substrate-particle binding strength on the vibrational Q-factor of lithographically prepared gold nanodisks on glass. Weak and strong binding is realized through titanium adhesion layers of variable thickness. We find that strong binding leads to the generation of several new acoustic modes with varying Q-factors that depend on the particle aspect ratio and substrate material. Our work proposes an approach to tune enhanced acoustic Q-factors of lithographically prepared nanoparticles and offers a comprehensive description of their damping mechanism.