Electronic and structural characterization of barrier-type amorphous aluminium oxide

Evangelisti, Fabio; Stiefel, Michael; Guseva, Olga; Nia, Raheleh Partovi; Hauert, Roland; Hack, Erwin; Jeurgens, Lars P. H.; Ambrosio, Francesco; Pasquarello, Alfredo; Schmutz, Patrik; Cancellieri, Claudia

doi:10.1016/j.electacta.2016.12.090

Cited by 25 publications

(29 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Al 2 O 3 ) and amorphous, in line with previous findings. 22 For the Al99.5 substrate, higher final current densities after 600 s dwell time were observed for increasing V anod ( Figure 1A). The increase of the residual current with the V anod is typical for the growth of compact, barrier-type oxide layers, in which ionic migration and related space charge recombination processes are effectively hindered.…”

Section: Anodic Oxide Growth and Morphology-mentioning

confidence: 89%

“…For each angle, the UV-Vis spectra were collected in the wavelength range of 370-1720 nm with an integration times of 5 s. The layer thickness was evaluated from the measured series of spectra, according to an established procedure. 22 Atomic-Force-Microscopy-based Scanning Kelvin probe force microscopy (AFM-SKPFM) was employed to gain information on the surface potential and surface roughness of the anodized oxide layers. The surface characterizations were performed with a Bruker Nano Environmental AFM (E-SCOPE) system using a Pt-Ir metallic coated tip with a resonance frequency of f res = 100 kHz and a nominal spring constant k = 2.8 Nm −1 .…”

Section: Experimental: Materials and Methodsmentioning

confidence: 99%

“…Anodizing of metals and alloys in organic electrolytes of controlled pH (5)(6)(7), such as oxalic and citric acids, generally results in the formation of dense and low-defective barrier oxide layers with relatively low electrolyte impurity concentrations. 11,22,23 Nevertheless, the incorporation of minor impurity concentrations from the electrolyte solution into the grown Al 2 O 3 barrier layer seems unavoidable. For organic/aqueous electrolyte solutions, H-and C-containing species are the main impurities in the anodically grown oxide layer.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

González‐Castaño

Döbeli

Araullo‐Peters

et al. 2018

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

A comprehensive study concerning the effect of different Al metal substrate purities (i.e. 99.5 versus 99.99%) on the properties of amorphous anodic barrier Al 2 O 3 is presented. The experimental findings demonstrate that only tiny variations in the purity of the employed Al materials lead to different oxide growth rate, surface charge, structural defect and impurities content. Below the ionic recombination potential characterized by Scanning Kelvin Probe Force Microscopy, an increase of the anodizing voltage leads to an improvement of the oxide barrier properties. The larger growth rate exhibited by the higher purity Al substrate however indicates the formation of highly disordered and inhomogeneous barrier oxides. A combination of photoelectrochemical and photoluminescence spectroscopies was used to characterize structural defect concentration and confirmed the presence of significantly higher concentrations in the oxide grown on the purer Al substrates. FT-IR and RBS/ERDA results indicate that H and C species are incorporated from the electrolyte solution in the barrier oxides with higher H amounts detected in the oxide grown on the purer Al substrate.

show abstract

Section: Anodic Oxide Growth and Morphology-mentioning

confidence: 89%

Section: Experimental: Materials and Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

González‐Castaño

Döbeli

Araullo‐Peters

et al. 2018

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This implies that the AP shift for an atom in a given compound with respect to its reference state is proportional to the difference in extra atomic relaxation energy, which can be related to important physical properties, such as the electronic polarizability, the dielectric constant or the relative density. [31][32][33] By analyzing the kinetic energy difference between a core-level photoelectron and its The higher the energy of the applied X-ray excitation source, the higher the kinetic energy of the detected core-level photoelectrons. On the contrary, detected core-core Auger electrons have a fixed kinetic energy, independent of the X-ray excitation energy.…”

Section: Figurementioning

confidence: 99%

Concepts for chemical state analysis at constant probing depth by lab‐based XPS/HAXPES combining soft and hard X‐ray sources

Siol

Mann²,

Newman³

et al. 2020

Surface & Interface Analysis

Self Cite

View full text Add to dashboard Cite

The greater information depth provided in Hard X-ray Photoelectron Spectroscopy (HAXPES) enables non-destructive analyses of the chemistry and electronic structure of buried interfaces. Moreover, for industrially relevant elements like Al, Si and Ti, the combined access to the Al 1s, Si 1s or Ti 1s photoelectron line and its associated Al KLL, Si KLL or Ti KLL Auger transition, as required for local chemical state analysis on the basis of the Auger parameter, is only possible with hard X-rays. Until now, such photoemission studies were only possible at synchrotron facilities. Recently however, the first commercial XPS/HAXPES systems, equipped with both soft and hard X-ray sources, have entered the market, providing unique opportunities for monitoring the local chemical state of all constituent ions in functional oxides at different probing depths, in a routine laboratory environment. Bulksensitive shallow core-levels can be excited using either the hard or soft X-ray source, whereas more surface-sensitive deep core-level photoelectron lines and associated Auger transitions can be measured using the hard X-ray source. As demonstrated for thin Al2O3, SiO2 and TiO2 films, the local chemical state of the constituting ions in the oxide may even be probed at near constant probing depth by careful selection of sets of photoelectron and Auger lines, as excited with the combined soft and hard X-ray sources. We highlight the potential of lab-based HAXPES for the research on functional oxides and also discuss relevant technical details regarding the calibration of the kinetic binding energy scale. Supporting information:Advanced chemical state studies of oxide films by lab-based HAXPES combining soft and hard X-ray sources

show abstract

“…Citric acid (1 M, adjusted to a pH 5.8) was chosen as electrolyte, since previous work showed that dense barrier oxide containing very low amounts of impurity contamination from the electrolyte can be obtained. 32 The potential was applied between the metallic precursor exposed surface and a Pt counter electrode. The potential was ramped at 6 V/s to the final voltage and subsequently held for 50 s and 100 s for samples anodized at 90 V and 30 V, respectively.…”

Section: Synthesismentioning

confidence: 99%

Anodizing of Self-Passivating W_xTi_1–x Precursors for W_xTi_1–xO_n Oxide Alloys with Tailored Stability

Siol

Beall

Ott

et al. 2019

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

TiO2 and WO3 are two of the most important, industrially relevant earth-abundant oxides. Although both materials show complementary functionality and are promising candidates for similar types of applications such as catalysis, sensor technology, and energy conversion, their chemical stability in reactive environments differs remarkably. In this study, anodic barrier oxides are grown on solid-solution WxTi1-x alloy precursors covering a wide compositional range (0 x 1) with the goal of creating functional oxides with tailored stability. A strong Ti-cation enrichment in the surface region of the grown WxTi1-xOn layer is observed, which can be controlled by both the anodizing conditions and precursor composition. For Ti concentrations above 50 at. %, a continuous nanometer-thick TiO2 protective coating is achieved on top of a homogeneous WxTi1-xOn film as evidenced by X-ray photoelectron spectroscopy and transmission electron microscopy analyses. A comprehensive electrochemical assessment demonstrates a very stable passivation of the surface in both acidic and alkaline environments. This increase in chemical stability correlates directly with the presence of this protective TiO2 film. The results of this work provide insights into the oxidation behavior of W1-xTix alloys, but more importantly demonstrate how controlled oxidation of self-passivating alloys can lead to oxide alloys with thin, protective surface layers that otherwise would require more sophisticated deposition methods.

show abstract

Electronic and structural characterization of barrier-type amorphous aluminium oxide

Cited by 25 publications

References 61 publications

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

Concepts for chemical state analysis at constant probing depth by lab‐based XPS/HAXPES combining soft and hard X‐ray sources

Anodizing of Self-Passivating W_xTi_1–x Precursors for W_xTi_1–xO_n Oxide Alloys with Tailored Stability

Contact Info

Product

Resources

About

Electronic and structural characterization of barrier-type amorphous aluminium oxide

Cited by 25 publications

References 61 publications

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al2O3

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al2O3

Concepts for chemical state analysis at constant probing depth by lab‐based XPS/HAXPES combining soft and hard X‐ray sources

Anodizing of Self-Passivating WxTi1–x Precursors for WxTi1–xOn Oxide Alloys with Tailored Stability

Contact Info

Product

Resources

About

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

Anodizing of Self-Passivating W_xTi_1–x Precursors for W_xTi_1–xO_n Oxide Alloys with Tailored Stability