Strong Spreading in a Droplet Flow for Low-Dimensional Nanostructures Growth

TL;DR

This study uses in situ TEM to observe indium droplet spreading on a silicon nitride surface, revealing complex nanofluidic behaviors driven by reactive spreading and crystallization, advancing understanding of low-dimensional nanostructure growth.

Contribution

It provides the first in situ visualization and analysis of droplet-driven nanostructure growth, linking experimental observations with theoretical models of reactive spreading and wettability gradients.

Findings

Strong droplet spreading on a-Si:H surface observed

Temperature-dependent droplet behaviors including break-up and nanowire formation

Validation of de Gennes' theory in nanofluidic droplet dynamics

Abstract

We report an in situ transmission electron microscopy observation of an indium droplet flowing on a silicon nitride membrane with a coating layer of hydrogenated amorphous silicon (a-Si:H), with the production of in-plane c-Si nanowire in its trail. We observe that the droplet strongly spreads on the a-Si:H coated surface while it dewets from the c-Si NW. This in situ observation, combined with the geometric analysis of such liquid-solid systems, presents nice consistency with de Gennes theoretic prediction of the droplet hydrodynamics steered by reactive spreading, where the wettability gradient for the droplet flowing is maintained by a progressively autophobic process due to the droplet mediated crystallization of a-Si:H. Interestingly, we record temperature dependent evolution of the droplet-nanowire interface, which leads the droplet break-up, self-turning and the nanoflake-to-nanowire transition. We elucidate these rich nanofluidic phenomena by a model based on the heterogeneous nucleation governed reactive spreading.