Characterization of nanocrystalline-nanoporous nickel oxide thin films prepared by reactive advanced gas deposition

• Published in: Materials chemistry and physics Vol. 227; pp. 98 - 104
• Main Authors: Cindemir, U., Topalian, Z., Granqvist, C.G., Österlund, L., Niklasson, G.A.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.04.2019; Elsevier BV
• Subjects: Actuators; Advanced gas deposition; Annealing; Atomic structure; Deposition; Engineering Science with specialization in Solid State Physics; EXAFS; Fine structure; Gas sensor; Gas sensors; Grain growth; Heat treatment; Morphology; Nanocrystals; Nanoparticles; Nickel oxide; Nickel oxides; Oxide coatings; Photoelectrons; Scanning electron microscopy; Sensors; Structural analysis; Substrates; Teknisk fysik med inriktning mot fasta tillståndets fysik; Thick films; Thin films; Variations; X ray absorption; Gas sensor; Advanced gas deposition; Atomic structure; Nickel oxide; EXAFS
• ISSN: 0254-0584; 1879-3312; 1879-3312
• DOI: 10.1016/j.matchemphys.2019.01.058

Nanocrystalline-nanoporous Ni oxide is of much interest for gas sensors and other applications. Reactive advanced gas deposition (AGD) stands out as a particularly promising technique for making thin films of this material owing to the technique's ability to separate between the growth of individual nanoparticles and their subsequent deposition to create a consolidated material on a substrate. Here we report on the characterization of Ni oxide films, made by reactive AGD, by several methods. X-ray diffractometry showed that the films had a face centered cubic NiO structure, and scanning electron microscopy indicated a compact nanoparticulate composition. X-ray photoelectron spectroscopy showed the presence of Ni3+ and demonstrated that these states became less prominent upon heat treatment in air. Extended x-ray absorption fine structure analysis elucidated the local atomic structure; in particular, data on interatomic distances and effects of annealing on local disorder showed that the Ni oxide nanoparticles crystallize upon annealing while maintaining their nanoparticle morphology, which is a crucial feature for reproducible fabrication of Ni oxide thin films for gas sensors. Importantly, several techniques demonstrated that grain growth remained modest for annealing temperatures as high as 400 °C for 1700-nm-thick films. The present article is a sequel to an earlier one [U. Cindemir et al., Sensors and Actuators B 242 (2017) 132–139] in which we reported on fluctuation-enhanced and conductometric gas sensing with Ni oxide films prepared by AGD. •Nanoporous films of NiO were produced by advanced gas deposition (AGD).•The crystallinity improves upon annealing while grain growth is modest.•AGD is a promising method to deposit NiO films for gas sensor applications.