Nanoparticles obtained via solid state dewetting of silver thin film

Introduction  Ordered metallic nano-particles can exhibit unique properties of light scattering, confinement and absorption, prominent for a vast number of applications (energy harvesting, bio-sensing, surface enhanced Raman... [ view full abstract ]

Introduction 

Ordered metallic nano-particles can exhibit unique properties of light scattering, confinement and absorption, prominent for a vast number of applications (energy harvesting, bio-sensing, surface enhanced Raman spectroscopy etc). However, deposition of such arrays over macroscopic surfaces remains challenging.

Among various methods known for the fabrication of metal nano-particles, we chose the solid-state dewetting of very thin metallic films. This technique alone results in randomly distributed islands with an important size distribution. But if the metal layer is deposed on a patterned surface, the dewetting results in the arrays of metallic nano-particles.

Methods

The morphology and optical properties of our samples are examined both post-mortem and through the combination of in situ and real-time techniques (environmental scanning electron microscopy and spectroscopic ellipsometry).

Results

In this contribution, we demonstrate how nano-imprint process combined to silver dewetting leads to an innovative, simple and scalable approach for fabrication of silver nano-particles arrays (Fig.1). It allows us to drastically increase the fabrication scalability and obtain the 8×8 cm² sample. Moreover, this new technique is not limited to wafer-based substrates and can be applied on transparent substrates such as glass, which paves a way for optical characterization in transmission.

Figure 1. SEM images treated of arrays of nanoparticles obtained through the dewetting of silver layer deposited on patterned silica surface (square array, lattice constant varied in range from 200 to 1000 nm)

DiscussionWe prove the excellent organization of our silver nano-particles array showing both order and uniform size distribution. We control the size and organization of particles with the initial thickness and graininess of the silver film and the period of patterns. Finally we investigate both experimentally and through numerical simulations the optical properties of these surfaces containing the arrangement of nano-particles and in particular the position of the surface lattice resonance with respect to lattice constant of the array.