Growth of NiO Thin Films in the Presence of Water Vapor: Insights from Experiments and Theory

Abstract

NiO-based thin films and nanomaterials are promising candidates for a variety of end-uses, encompassing photo- and electrocatalysts, solar cells, displays, and sensors. This widespread attention has strongly fueled the interest in the fabrication of tailored systems featuring modular chemico-physical properties as a function of the required application. In this study, a single-step chemical vapor deposition (CVD) route for the preparation of pure and fluorine-doped NiO films is presented. Growth experiments were performed under water vapor-containing oxygen atmospheres from a series of Ni­(II) β-diketonate–diamine molecular precursors featuring a different fluorination degree of the ligand side chain. A comprehensive experimental and theoretical investigation yielded valuable insights into the growth mechanism, with particular regard to the dependence of the system electronic properties on fluorine doping and content, and to the role exerted by water vapor in the reaction atmosphere. In fact, the interactions of water with the diketonate ligands contribute to weaken Ni–O bonds, favoring precursor activation. The obtainment of F-doped NiO systems from fluorinated derivatives and the simplicity of our process make the adopted strategy a valuable tool to control the system characteristics for a variety of eventual functional applications.

On the Fragmentation of Ni(II) β-Diketonate-Diamine Complexes as Molecular Precursors for NiO Films: A Theoretical and Experimental Investigation

“…In order to circumvent these problems, following our previous works on homologous first-row transition metal complexes [30,31,[41][42][43][44][45], we have focused on the preparation and characterization of Ni(II) β-diketonate-diamine compounds of the general formula NiL 2 TMEDA [HL = 1,1,1,-trifluoro-2,4-pentanedionate (tfa), 2,2-dimethyl-6,6,7,7,8,8,8heptafluoro-3,5-octanedionate (fod), or thd; TMEDA = N,N,N ′ ,N ′ -tetramethylethylenediamine]. The results of a comprehensive experimental and theoretical investigation [46,47] highlighted that these compounds offer several amenable characteristics as CVD precursors of NiO films with modular properties. Insights into the compound reactivity were previously obtained by electron ionization mass spectrometry (EI-MS) [46], typically considered more appropriate for the investigation of CVD precursor gas-phase reactivity, especially in plasma-assisted processes [46].…”