Publication detail

Hafnium-Oxide 3-D Nanofilms via the Anodizing of Al/Hf Metal Layers

MOZALEV, A. BENDOVÁ, M. GISPERT-GUIRADO, F. LLOBET, E.

Original Title

Hafnium-Oxide 3-D Nanofilms via the Anodizing of Al/Hf Metal Layers

Type

journal article in Web of Science

Language

English

Original 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.

Keywords

OXIDATION; ANODIZATION; ALUMINUM; GROWTH; FILM; ACID; XPS; ZIRCONIUM; TANTALUM; NIOBIUM

Authors

MOZALEV, A.; BENDOVÁ, M.; GISPERT-GUIRADO, F.; LLOBET, E.

Released

24. 4. 2018

ISBN

0897-4756

Periodical

CHEMISTRY OF MATERIALS

Year of study

30

Number

8

State

United States of America

Pages from

2694

Pages to

2708

Pages count

15

BibTex

@article{BUT147223,
  author="Alexander {Mozalev} and Mária {Bendová} and Francesc {Gispert-Guirado} and Eduard {Llobet}",
  title="Hafnium-Oxide 3-D Nanofilms via the Anodizing of Al/Hf Metal Layers",
  journal="CHEMISTRY OF MATERIALS",
  year="2018",
  volume="30",
  number="8",
  pages="2694--2708",
  doi="10.1021/acs.chemmater.8b00188",
  issn="0897-4756"
}