Impact of Different Intermediate Layers on the Morphology and Crystallinity of TiO2 Grown on Carbon Nanotubes by Atomic Layer Deposition

Abstract

Nanocomposites of TiO2 and carbon nanotubes (CNTs) have been extensively studied in photocatalysis, sensing, and energy conversion and storage over the last decade. The unique properties of these nanocomposites are greatly dependent on the morphology, crystallinity, and homogeneity of the TiO2 coating. However, a fine control of the film microstructure is still challenging due to limited understanding of early stages of the TiO2 growth. The presence of an intermediate buffer layer can induce remarkable changes in the morphological and structural characteristics of the coatings. Here, TiO2 films deposited by atomic layer deposition (ALD) on CNTs without and with different intermediate layers (Al2O3 and ZnO) have been systematically investigated. Compared to bare CNTs, it is suggested that these two intermediate layers with higher surface energy can lead to a delay of the TiO2 crystallization, ultimately resulting in the growth of conformal and crystalline TiO2 films. This study demonstrates a strategy to tailor the microstructure and the properties of thin films via ALD by applying intermediate layers and provides information about the role of surface energy of the substrate in crystallization and growth behavior of ALD thin films.