Thermodynamic Control of Nanoparticle Fabrication via Confined Dewetting.

Abstract

Dewetting, a phenomenon studied for over a century, has broad applications across diverse areas. When thin metal films deposited on flat substrates are heated, they undergo dewetting and typically form nanoparticles whose size and spacing are influenced by parameters such as film thickness, substrate surface energy, annealing temperature, and surface diffusion kinetics. In conventional dewetting, these factors often result in broad particle size distributions and irregular interparticle spacings due to uncontrolled thermal fluctuations and instabilities. Controlling dewetting to produce high-density nanoparticles with narrow size distributions and single-digit nanometre interparticle separations is a very difficult task and requires complex and expensive fabrication techniques. Here, a scalable, cost-effective method for producing high-density and low-dispersity metal nanoparticles on various substrates with flat, curved, and microtextured surfaces is presented. By creating a confined environment with a Polydimethylsiloxane (PDMS) layer atop the film during dewetting, pure metal and alloy nanoparticles with high density, low size variation, and high purity are obtained. Theoretical analysis suggests that the elasticity and reduced surface tension of PDMS lower the energy associated with surface fluctuations, which in turn reduces particle size. This approach provides a straightforward route for fabricating low-dispersity, high-density nanoparticles through a simple confined-dewetting method, with widespread applications.