Author, as appears in the article.: Mozalev A., Bendova M., Gispert-Guirado F., Llobet E.

Department: Enginyeria Electrònica, Elèctrica i Automàtica

URV's Author/s: Gispert Guirado, Francesc / GUIRADO PAGÉS, FRANCISCO / Llobet Valero, Eduard

Keywords: Metals Oxides

Abstract: Hafnium-oxide films with self-organized nanostructured 3-D architectures and variable dimension (10 to 400 nm) are synthesized via the high-current anodizing of thin aluminum-on-hafnium layers in phosphoric, malonic, and oxalic acid electrolytes. In the approach, the self-organized growth of a porous anodic alumina (PAA) film is immediately followed by the fast PAA-assisted reanodizing of the hafnium underlayer. The PAA-dissolved films consist of arrays of upright-standing hafnium-oxide nanorods held on the substrate by the tiny needle-like "nanoroots" widespread over a continuous hafnium-oxide bottom layer. The roots are amorphous Hf2O3, while the rods are amorphous HfO2-Hf2O3-Al2O3 mixed oxides, the bottom layer being, however, highly textured nanocrystalline HfO2. The calculated transport numbers for O2- and Hf4+(3)+ ions are, respectively, ∼0.55 and ∼0.45, which is a unique situation for anodic hafnium oxide, which normally grows by O2- transport only. Annealing the films in air at 600 °C oxidizes the remaining Hf metal to polycrystalline HfO2, still leaving the roots and rods amorphous. The annealing in vacuum results in partial oxide reduction and crystallization of the roots and rods to stable orthorhombic and monoclinic HfO2 phases. A model of the anodic film growth and solid-state ionic transport is proposed and experimentally justified. Potential applications of the 3-D hafnium-oxide nanofilms are in advanced electronic, photonic, or magnetic micro- and nanodevices.

Thematic Areas: Química Medicina ii Materials science, multidisciplinary Materials science Materials chemistry Materiais Interdisciplinar Geociências General chemistry General chemical engineering Farmacia Engenharias iv Engenharias iii Engenharias ii Engenharias i Ciências biológicas i Ciências ambientais Chemistry, physical Chemistry (miscellaneous) Chemistry (all) Chemical engineering (miscellaneous) Chemical engineering (all) Biotecnología Biodiversidade Astronomia / física

licence for use: https://creativecommons.org/licenses/by/3.0/es/

ISSN: 08974756

Author's mail: eduard.llobet@urv.cat

Author identifier: 0000-0001-6164-4342

Record's date: 2023-02-22

Papper version: info:eu-repo/semantics/acceptedVersion

Link to the original source: https://pubs.acs.org/doi/10.1021/acs.chemmater.8b00188

Licence document URL: http://repositori.urv.cat/ca/proteccio-de-dades/

Papper original source: Chemistry Of Materials. 30 (8): 2694-2708

APA: Mozalev A., Bendova M., Gispert-Guirado F., Llobet E. (2018). Hafnium-Oxide 3‑D Nanofilms via the Anodizing of Al/Hf Metal Layers. Chemistry Of Materials, 30(8), 2694-2708. DOI: 10.1021/acs.chemmater.8b00188

Article's DOI: 10.1021/acs.chemmater.8b00188

Entity: Universitat Rovira i Virgili

Journal publication year: 2018

Publication Type: Journal Publications