Electronic Phenomena of Transition Metal Oxides Volume II

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: 10 August 2024 | Viewed by 9029

Special Issue Editors


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Guest Editor
August Chelkowski Institute of Physics, University of Silesia, 40-007 Katowice, Poland
Interests: perovskites; dislocations; phase transitions; resistive switching
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Guest Editor
Forschungszentrum Jülich, Institute of Energy and Climate Research/Electrochemical Process Engineering (IEK-14), Jülich, Germany
Interests: solid oxides; perovskites; electrochemistry; renewable energy; surface physics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Reducing the energy consumption of electronic devices while increasing their functionality remains a major task for research and development. Since new materials are needed for this purpose, the study of electronic- and crystallographic-structure and lattice dynamics, as well as machine learning of single- and multi-ternary transition metal oxides, is becoming increasingly important. Electromechanics, superconductivity, resistive switching, photovoltaics, or energy storage are a few examples of applications for transition metal oxides. With the ongoing miniaturization of electronic components, nanoscale properties must be understood in detail, which demands measurement techniques with high spatial resolution to be employed. In this context, on the one hand, the analysis of redox processes and the interplay of electronic and ionic conductivity, point defects, and extended defects must be investigated to understand the complexity of the chemistry and electrochemistry of transition metal oxides. On the other hand, the nature of the screening phenomena in the presence of ordering parameters should be investigated at the atomic level.

This Special Issue provides a platform for sharing recent results on the electronic properties of transition metal oxides on the nanoscale using advanced experimental methods in combination with theoretical analyses.

Prof. Dr. Krzysztof Szot
Dr. Christian Rodenbücher
Guest Editors

Manuscript Submission Information

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Keywords

  • metal–insulator transitions and superconductivity
  • atomistic processes at surfaces, interfaces, and extended defects
  • electronic structure and lattice dynamics
  • redox reactions and oxygen transport
  • segregation and phase transformations
  • multiferroic properties
  • machine learning for transition metal oxides design and discovery

Published Papers (5 papers)

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Research

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12 pages, 5377 KiB  
Article
Influence of Defects-Induced Stresses on Birefringence in SrTiO3 Single Crystals
by Iwona Lazar, Krzysztof Szot and Krystian Roleder
Crystals 2023, 13(7), 985; https://doi.org/10.3390/cryst13070985 - 21 Jun 2023
Cited by 1 | Viewed by 851
Abstract
Significant applications of SrTiO3 single crystals in electronics require knowledge about the influence of structural imperfections on their optical properties. Birefringence temperature changes were investigated in a few SrTiO3 single crystals in a broad temperature range, from 85 K to 250 [...] Read more.
Significant applications of SrTiO3 single crystals in electronics require knowledge about the influence of structural imperfections on their optical properties. Birefringence temperature changes were investigated in a few SrTiO3 single crystals in a broad temperature range, from 85 K to 250 K. The birefringence was found to be a non-linear function below the transition Ts at 105 K, and non-linear changes in the optical indicatrix orientation accompanied it. A weak residual birefringence was permanently present a dozen degrees above the phase transition temperature Ts. This is mainly connected with dislocations, which induce local stresses and shift transition points even up to about 200 K. The essential role of imperfections on optical properties was studied in a SrTiO3 24° bi-crystal reduced at 1000 K and under low oxygen pressure. In such an intentionally defected crystal, an increase of non-linearities in Δn(T) dependence was observed below and above the transition point Ts. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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11 pages, 5235 KiB  
Article
Electrostimulation and Nanomanipulation of Two-Dimensional MoO3-x Layers Grown on Graphite
by Aleksandra Nadolska, Dorota A. Kowalczyk, Iaroslav Lutsyk, Michał Piskorski, Paweł Krukowski, Paweł Dąbrowski, Maxime Le Ster, Witold Kozłowski, Rafał Dunal, Przemysław Przybysz, Wojciech Ryś, Klaudia Toczek, Paweł J. Kowalczyk and Maciej Rogala
Crystals 2023, 13(6), 905; https://doi.org/10.3390/cryst13060905 - 1 Jun 2023
Cited by 2 | Viewed by 1339
Abstract
Molybdenum trioxide shows many attractive properties, such as a wide electronic band gap and a high relative permittivity. Monolayers of this material are particularly important, as they offer new avenues in optoelectronic devices, e.g., to alter the properties of graphene electrodes. Nanoscale electrical [...] Read more.
Molybdenum trioxide shows many attractive properties, such as a wide electronic band gap and a high relative permittivity. Monolayers of this material are particularly important, as they offer new avenues in optoelectronic devices, e.g., to alter the properties of graphene electrodes. Nanoscale electrical characterization is essential for potential applications of monolayer molybdenum trioxide. We present a conductive atomic force microscopy study of an epitaxially grown 2D molybdenum oxide layer on a graphene-like substrate, such as highly oriented pyrolytic graphite (HOPG). Monolayers were also investigated using X-ray photoelectron spectroscopy, atomic force microscopy (semi-contact and contact mode), Kelvin probe force microscopy, and lateral force microscopy. We demonstrate mobility of the unpinned island under slight mechanical stress as well as shaping and detachment of the material with applied electrical stimulation. Non-stoichiometric MoO3-x monolayers show heterogeneous behavior in terms of electrical conductivity, which can be related to the crystalline domains and defects in the structure. Different regions show various I–V characteristics, which are correlated with their susceptibility to electrodegradation. In this work, we cover the existing gap regarding nanomanipulation and electrical nanocharacterization of the MoO3 monolayer. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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14 pages, 4498 KiB  
Article
Theoretical Study on (n,n)-Nanotubes Rolled-up from B/N Substituted Me-Graphene
by Hong-Chao Luo, Feng-Yin Li, Ya-Nan Zhang, Hong-Xing Zhang, Roberts I. Eglitis and Ran Jia
Crystals 2023, 13(5), 829; https://doi.org/10.3390/cryst13050829 - 17 May 2023
Cited by 1 | Viewed by 1278
Abstract
In this work, the n,n-type nanotube systems rolled up from the B/N substituted Me-graphene (i.e., Me-CBNT and Me-CNN, respectively) were investigated with the aid of the density functional theory (DFT). Due to the lattice dynamic instabilities until n=10 [...] Read more.
In this work, the n,n-type nanotube systems rolled up from the B/N substituted Me-graphene (i.e., Me-CBNT and Me-CNN, respectively) were investigated with the aid of the density functional theory (DFT). Due to the lattice dynamic instabilities until n=10, the n,0 and n,m nanotube systems were not involved in this study. According to our calculations at the Perdew-Burke-Ernzerhof (PBE) level, the n,n Me-CBNT and Me-CNNT systems possess excellent mechanical strengths. The Young’s moduli of Me-CBNTs can reach 60% of single-walled carbon nanotubes (SWCNTs), while their mass densities are only around 70% of SWCNTs. Based on the fully relaxed geometric configurations at the PBE level, the electronic configurations of the related nanotubes were evaluated by using the global hybrid functional B3LYP with 36% Fock exchanges. The n,n Me-CBNTs are metallic, while the n,n Me-CNNTs are semiconductors with the inherent band gaps in the range of 3.08 eV to 3.31 eV. The Bloch flat bands appear on both sides of their Fermi levels, indicating the localized charge carriers. Their band edge arrangements imply that these materials are promising candidates for the photocatalytic water splitting reactions at certain pH values. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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Review

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17 pages, 7035 KiB  
Review
The Effect of Reduction and Oxidation Processes on the Work Function of Metal Oxide Crystals: TiO2(110) and SrTiO3(001) Case
by Karol Cieślik, Dominik Wrana, Maciej Rogala, Christian Rodenbücher, Krzysztof Szot and Franciszek Krok
Crystals 2023, 13(7), 1052; https://doi.org/10.3390/cryst13071052 - 3 Jul 2023
Cited by 3 | Viewed by 1582
Abstract
The strict control of the work function of transition metal oxide crystals is of the utmost importance not only to fundamental research but also to applications based on these materials. Transition metal oxides are highly abundant in electronic devices, as their properties can [...] Read more.
The strict control of the work function of transition metal oxide crystals is of the utmost importance not only to fundamental research but also to applications based on these materials. Transition metal oxides are highly abundant in electronic devices, as their properties can be easily modified using redox processes. However, this ease of tuning is a double-edged sword. With the ease of manipulation comes difficulty in controlling the corresponding process. In this study, we demonstrate how redox processes can be induced in a laboratory setting and how they affect the work function of two model transition metal oxide crystals, namely titanium dioxide TiO2(110) and strontium titanate SrTiO3(001). To accomplish this task, we utilized Kelvin Probe Force Microscopy (KPFM) to monitor changes in work function, Scanning Tunneling Microscopy (STM), and Low-Energy Electron Diffraction (LEED) to check the surface morphology and reconstruction, and we also used X-ray Photoelectron Spectroscopy (XPS) to determine how the surface composition evolves. We also show that using redox processes, the work function of titanium dioxide can be modified in the range of 3.4–5.0 eV, and that of strontium titanate can be modified in the range of 2.9–4.5 eV. Moreover, we show that the presence of an oxygen-gaining material in the vicinity of a transition metal oxide during annealing can deepen the changes to its stoichiometry and therefore the work function. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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25 pages, 6361 KiB  
Review
Review of First Principles Simulations of STO/BTO, STO/PTO, and SZO/PZO (001) Heterostructures
by Roberts I. Eglitis, Dmitry Bocharov, Sergey Piskunov and Ran Jia
Crystals 2023, 13(5), 799; https://doi.org/10.3390/cryst13050799 - 10 May 2023
Cited by 19 | Viewed by 3267
Abstract
In this study, we review our first-principles simulations for STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures. Specifically, we report ab initio B3PW calculations for STO/BTO, STO/PTO, and SZO/PZO (001) interfaces, considering non-stoichiometric heterostructures in the process. Our ab initio B3PW calculations demonstrate that charge [...] Read more.
In this study, we review our first-principles simulations for STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures. Specifically, we report ab initio B3PW calculations for STO/BTO, STO/PTO, and SZO/PZO (001) interfaces, considering non-stoichiometric heterostructures in the process. Our ab initio B3PW calculations demonstrate that charge redistribution in the (001) interface region only subtly affects electronic structures. However, changes in stoichiometry result in significant shifts in band edges. The computed band gaps for the STO/BTO, STO/PTO, and SZO/PZO (001) interfaces are primarily determined according to whether the topmost layer of the augmented (001) film has an AO or BO2 termination. We predict an increase in the covalency of B-O bonds near the STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures as compared to the BTO, PTO, and PZO bulk materials. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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