Template-controlled mineralization: Determining film granularity and structure by surface functionality patterns

TL;DR

Scientists show how to control the structure of a mineral film by using different surface patterns, which affects the film's texture and properties.

Contribution

The study demonstrates how surface functionality patterns can control the granularity and morphology of self-assembling zinc oxide films.

Findings

Fluorinated surfaces produce coarse-grained films with agglomerates around 75 nm.

Amino-functionalized surfaces result in smooth, fine-grained films with 1 nm roughness.

Surface adhesion energy and nanoparticle diffusion rates explain the morphological differences.

Abstract

We present a promising first example towards controlling the properties of a self-assembling mineral film by means of the functionality and polarity of a substrate template. In the presented case, a zinc oxide film is deposited by chemical bath deposition on a nearly topography-free template structure composed of a pattern of two self-assembled monolayers with different chemical functionality. We demonstrate the template-modulated morphological properties of the growing film, as the surface functionality dictates the granularity of the growing film. This, in turn, is a key property influencing other film properties such as conductivity, piezoelectric activity and the mechanical properties. A very pronounced contrast is observed between areas with an underlying fluorinated, low energy template surface, showing a much more (almost two orders of magnitude) coarse-grained film with a typical agglomerate size of around 75 nm. In contrast, amino-functionalized surface areas induce the growth of a very smooth, fine-grained surface with a roughness of around 1 nm. The observed influence of the template on the resulting clear contrast in morphology of the growing film could be explained by a contrast in surface adhesion energies and surface diffusion rates of the nanoparticles, which nucleate in solution and subsequently deposit on the functionalized substrate.

Figures