Electrochemical Oxidation of Hf–Nb Alloys as a Valuable Route to Prepare Mixed Oxides of Tailored Dielectric Properties

Abstract

Metal oxides with high dielectric constant are extensively studied in the frame of substituting SiO2 as gate dielectric in nanoelectronic devices. Here, high‐k mixed HfO2/Nb2O5 oxides are prepared by a facile electrochemical route starting from sputtering‐deposited Hf–Nb alloys with several compositions. Transmission electron microscopy, grazing incidence X‐ray diffraction, and glow discharge optical emission spectroscopy are employed to study the oxide structures, disclosing a crystalline–amorphous transition of the electrochemically prepared oxides by increasing the Nb content. Photo‐electrochemical measurements allow the observation of optical transitions ascribed to localized states inside oxide bandgap induced by the presence of oxygen vacancies for Hf‐rich oxides. Impedance measurements, coupled with withstand voltage and leakage current estimates, provide a comprehensive view of the real dielectric properties of the oxides. The highest ε is estimated for the anodic oxide grown on Hf–39 at% Nb (i.e., 45) but thin film grown on Hf–57 at% Nb alloy shows the best dielectric properties, revealing high dielectric constant, high withstand voltage, and low leakage current. Promising equivalent oxide thickness (down to 0.38 nm) is estimated for the oxide thin layers. The electrochemical oxidation represents a valuable and reliable way to prepare high‐k thin oxide films with tailored and controlled dielectric properties.

A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

“…Band gap modeling of simple and complex oxides is of paramount importance for the application of such materials in numerous and important applications pertaining to different fields such as solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis, and electrocatalysis), microelectronics (high- k , high-band-gap materials and resistive random access memory (ReRAM)), and active and passive anticorrosive coatings. − Owing to this, the band structure calculation of solids and, notably, of oxides has been one of the most investigated subjects of materials science in the past 20 years or more . In spite of the rewarding achievements obtained in computing numerous solid-state properties of different materials, the prediction of band gap values of materials is still a formidable task also for the most advanced quantum mechanical methods rooted on density functional theory (DFT). ,− …”

Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants

“…This is due to the barrier nature of the anodic film grown for 100 s, and the use of the EEC, as shown in Figure 4 a, is in agreement with that reported in the literature, for which the electrochemical behavior of barrier-like anodic films can be successfully modelled by a simple parallel RQ . 26 − 28 Conversely, in the case of AZ31 samples anodized for longer times (e.g., 30 and 60 min), a more complex EEC is needed to model the electrochemical behavior of anodic films immersed in HS. In particular, the EEC used is shown in Figure 4 b, where the parallel ( R b Q b ) is in series with R p representing the outer layer resistance, that is, the electrolyte resistance inside the pores of the anodic films.…”

Electrochemiluminescence of Carbon‐based Quantum Dots: Synthesis, Mechanism and Application in Heavy Metal Ions Detection

“…Compared with chemical oxidation, electrochemical oxidation only requires dialysis to purify CQDs. The electrochemical oxidation of impurities can change the oxidation state by applying an external voltage or releasing chemistry to transfer electrons between mole-cules or ions [33]. Zhou et al reported that CQDs with many oxygen-containing functional groups were prepared by cyclic voltammetry using multi-walled carbon nanotubes as working electrode [34].…”

“…Compared with chemical oxidation, electrochemical oxidation only requires dialysis to purify CQDs. The electrochemical oxidation of impurities can change the oxidation state by applying an external voltage or releasing chemistry to transfer electrons between molecules or ions [33]. Zhou et al.…”