On the role of micro-porosity in affecting the environmental stability of atomic/molecular layer deposited (ZnO)(Zn-O-CH-O) films.

Atomic/molecular layer deposited (ALD/MLD) inorganic-organic thin films form a novel class of materials with tunable properties. In selected cases, hybrid materials are reported to show environmental instability, specifically towards moisture. In this article, we focus on zinc oxide/zincone multi-layers with the theoretical formula of (ZnO)(a)(Zn-O-C6H4-O)(b). We show by means of ellipsometric porosimetry that microporosity in the range of 0.42 and 2 nm in the pristine zincone layer is responsible for its environmental degradation. During degradation, it is found that a relative micro-porosity content of 1.2 +/- 0.1 vol% in the pristine zincone films evolves into micro-mesoporosity with a relative content of 39 +/- 1 vol%. We also show that the micro-porosity in the zincone layer can be gradually suppressed when few cycles (a = 1-10) of ZnO are introduced. The resulting (ZnO)(a)(Zn-O-C6H4-O) b = 1 periodic multilayer is an environmentally stable film with a = 10. It is found that the suppressed micro-porosity is due to the development of continuous ZnO layers with a >= 10.