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15 pages, 3554 KiB

Open AccessArticle

Study of ZrO₂ Gate Dielectric with Thin SiO₂ Interfacial Layer in 4H-SiC Trench MOS Capacitors

by Qimin Huang, Yunduo Guo, Anfeng Wang, Zhaopeng Bai, Lin Gu, Zhenyu Wang, Chengxi Ding, Yi Shen, Hongping Ma and Qingchun Zhang

Materials 2025, 18(8), 1741; https://doi.org/10.3390/ma18081741 - 10 Apr 2025

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Abstract

The transition of SiC MOSFET structure from planar to trench-based architectures requires the optimization of gate dielectric layers to improve device performance. This study utilizes a range of characterization techniques to explore the interfacial properties of ZrO₂ and SiO₂/ZrO₂ [...] Read more.

The transition of SiC MOSFET structure from planar to trench-based architectures requires the optimization of gate dielectric layers to improve device performance. This study utilizes a range of characterization techniques to explore the interfacial properties of ZrO₂ and SiO₂/ZrO₂ gate dielectric films, grown via atomic layer deposition (ALD) in SiC epitaxial trench structures to assess their performance and suitability for device applications. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements showed the deposition of smooth film morphologies with roughness below 1 nm for both ZrO₂ and SiO₂/ZrO₂ gate dielectrics, while SE measurements revealed comparable physical thicknesses of 40.73 nm for ZrO₂ and 41.55 nm for SiO₂/ZrO₂. X-ray photoelectron spectroscopy (XPS) shows that in SiO₂/ZrO₂ thin films, the binding energies of Zr 3d_5/2 and Zr 3d_3/2 peaks shift upward compared to pure ZrO₂. Electrical characterization showed an enhancement of E_BR (3.76 to 5.78 MV·cm⁻¹) and a decrease of I_{ON_EBR} (1.94 to 2.09 × 10⁻³ A·cm⁻²) for the SiO₂/ZrO₂ stacks. Conduction mechanism analysis identified suppressed Schottky emission in the stacked film. This indicates that the incorporation of a thin SiO₂ layer effectively mitigates the small bandgap offset, enhances the breakdown electric field, reduces leakage current, and improves device performance. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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19 pages, 826 KiB

Open AccessArticle

Straight Disclinations in Fractional Nonlocal Medium

by Tamara Kyrylych and Yuriy Povstenko

Materials 2025, 18(8), 1717; https://doi.org/10.3390/ma18081717 - 9 Apr 2025

Viewed by 179

Abstract

The constitutive equation for a nonlocal stress tensor is represented as an integral with the suitable kernel function. In this paper, the nonlocality kernel is chosen as the Green function of the Cauchy problem for the fractional diffusion equation with the Caputo derivative [...] Read more.

The constitutive equation for a nonlocal stress tensor is represented as an integral with the suitable kernel function. In this paper, the nonlocality kernel is chosen as the Green function of the Cauchy problem for the fractional diffusion equation with the Caputo derivative with respect to the nonlocality parameter. The solutions of nonlocal elasticity problems for the straight wedge and twist disclinations in an infinite medium are obtained in the framework of this new nonlocal theory of elasticity. The Laplace integral transform with respect to the nonlocality parameter is used. It is necessary to emphasize that the transition from the nonlocal to local stress tensor is described by the limiting value of the nonlocality parameter

τ \to 0

. The obtained stress fields do not contain nonphysical singularities at the disclination lines. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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17 pages, 5606 KiB

Open AccessArticle

Optimizing Carbon Dot—TiO₂ Nanohybrids for Enhanced Photocatalytic Hydrogen Evolution

by Pinelopi P. Falara, Nikolaos Chatzikonstantinou, Adamantia Zourou, Polychronis Tsipas, Elias Sakellis, Eleni Alexandratou, Nektarios K. Nasikas, Konstantinos V. Kordatos and Maria Antoniadou

Materials 2025, 18(5), 1023; https://doi.org/10.3390/ma18051023 - 26 Feb 2025

Viewed by 542

Abstract

CDs/TiO₂ nanohybrids were synthesized and tested for photocatalytic H₂ production from aqueous media through simulated solar light-driven photocatalytic reactions. Firstly, three different types of CDs were prepared through green methods, specifically hydrothermal treatment and microwave irradiation, using citric acid and urea [...] Read more.

CDs/TiO₂ nanohybrids were synthesized and tested for photocatalytic H₂ production from aqueous media through simulated solar light-driven photocatalytic reactions. Firstly, three different types of CDs were prepared through green methods, specifically hydrothermal treatment and microwave irradiation, using citric acid and urea as precursors in varying molar ratios. After a multi-step purification procedure, impurity-free CDs were obtained. The as-synthesized CDs were thoroughly characterized using UV-Vis, FT-IR, and PL spectroscopy, along with HR-TEM. The results revealed that the size and optical and physicochemical properties of CDs can be tailored by selecting the precursors’ ratio and the synthetic approach. The heterostructured CDs/TiO₂ photocatalysts were formed solvothermally and were analyzed using UV-Vis/DRS, FT-IR, and XPS techniques, which confirmed the effective incorporation of CDs and the improved properties of TiO₂. The use of sacrificial reagents is among the most common strategies for enhancing H₂ production from water through photocatalytic processes; herein, ethanol was selected as a green liquid organic hydrogen carrier. A maximum H₂ production rate of 0.906 μmol H₂/min was achieved, while the recyclability study demonstrated that the photocatalyst maintained stable performance during multiple cycles of reuse. Thus, optimizing the synthesis conditions of CDs/TiO₂ nanohybrids resulted in the creation of environmentally friendly and reusable photocatalysts. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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32 pages, 26195 KiB

Open AccessArticle

Topology Design of Soft Phononic Crystals for Tunable Band Gaps: A Deep Learning Approach

by Jingru Li, Minqi Qian, Jingming Yin, Wei Lin, Zhifu Zhang and Shihao Liu

Materials 2025, 18(2), 377; https://doi.org/10.3390/ma18020377 - 15 Jan 2025

Viewed by 774

Abstract

The phononic crystals composed of soft materials have received extensive attention owing to the extraordinary behavior when undergoing large deformations, making it possible to provide tunable band gaps actively. However, the inverse designs of them mainly rely on the gradient-driven or gradient-free optimization [...] Read more.

The phononic crystals composed of soft materials have received extensive attention owing to the extraordinary behavior when undergoing large deformations, making it possible to provide tunable band gaps actively. However, the inverse designs of them mainly rely on the gradient-driven or gradient-free optimization schemes, which require sensitivity analysis or cause time-consuming, lacking intelligence and flexibility. To this end, a deep learning-based framework composed of a conditional variational autoencoder and multilayer perceptron is proposed to discover the mapping relation from the band gaps to the topology layout applied with prestress. The nonlinear superelastic neo-Hookean model is employed to describe the constitutive characteristics, based on which the band structures are obtained via the transfer matrix method accompanied with Bloch theory. The results show that the proposed data-driven approach can efficiently and rapidly generate multiple candidates applied with predicted prestress. The band gaps are in accord with each other and also consistent with the prescribed targets, verifying the accuracy and flexibility simultaneously. Furthermore, based on the generalization performance, the design space is deeply exploited to obtain desired soft structures whose stop bands are characterized by wider bandwidth, lower location, and enhanced wave attenuation performance. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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18 pages, 4252 KiB

Open AccessArticle

Bilayer TiO₂/Mo-BiVO₄ Photoelectrocatalysts for Ibuprofen Degradation

by Martha Pylarinou, Elias Sakellis, Spiros Gardelis, Vassilis Psycharis, Marios G. Kostakis, Nikolaos S. Thomaidis and Vlassis Likodimos

Materials 2025, 18(2), 344; https://doi.org/10.3390/ma18020344 - 14 Jan 2025

Viewed by 1029

Abstract

Heterojunction formation between BiVO₄ nanomaterials and benchmark semiconductor photocatalysts has been keenly pursued as a promising approach to improve charge transport and charge separation via interfacial electron transfer for the photoelectrocatalytic degradation of recalcitrant pharmaceutical pollutants. In this work, a heterostructured TiO [...] Read more.

Heterojunction formation between BiVO₄ nanomaterials and benchmark semiconductor photocatalysts has been keenly pursued as a promising approach to improve charge transport and charge separation via interfacial electron transfer for the photoelectrocatalytic degradation of recalcitrant pharmaceutical pollutants. In this work, a heterostructured TiO₂/Mo-BiVO₄ bilayer photoanode was fabricated by the deposition of a mesoporous TiO₂ overlayer using the benchmark P25 titania catalyst on top of Mo-doped BiVO₄ inverse opal films as the supporting layer, which intrinsically absorbs visible light below 490 nm, while offering improved charge transport. A porous P25/Mo-BiVO₄ bilayer structure was produced from the densification of the inverse opal underlayer after post-thermal annealing, which was evaluated on photocurrent generation in aqueous electrolyte and the photoelectrocatalytic degradation of the refractory anti-inflammatory drug ibuprofen under back-side illumination by visible and UV–Vis light. Significantly enhanced photoelectrochemical performance on both photocurrent density and pharmaceutical degradation was achieved for the bilayer structure with respect to the additive effect of the constituent layers, which was related to the improved light harvesting arising from the backscattering by the mesoporous TiO₂ layer in combination with the favorable charge transfer at the TiO₂/Mo-BiVO₄ interface. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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15 pages, 4530 KiB

Open AccessArticle

Thermal Optimization of Edge-Emitting Lasers Arrays

by Robert P. Sarzała, Dominika Dąbrówka and Maciej Dems

Materials 2025, 18(1), 107; https://doi.org/10.3390/ma18010107 - 30 Dec 2024

Viewed by 558

Abstract

This paper presents a novel approach to address the issue of uneven temperature distribution in one-dimensional laser arrays, specifically in gallium nitride edge-emitting lasers emitting green light of 540 nm. The results were obtained using heat flow numerical analysis, which included an optimization [...] Read more.

This paper presents a novel approach to address the issue of uneven temperature distribution in one-dimensional laser arrays, specifically in gallium nitride edge-emitting lasers emitting green light of 540 nm. The results were obtained using heat flow numerical analysis, which included an optimization method specifically developed for this type of array. It was demonstrated that thermal optimization of a one-dimensional edge-emitting laser array can be achieved by adjusting the placement of the emitters within the array and the size of the top gold contact, without changing the overall dimensions of the device. The proposed design alterations ensure an even temperature distribution across the array without the need for a complex and expensive cooling systems. The proposed optimization method can be applied to arrays made from various material systems, including nitrides, arsenides, and phosphides. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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10 pages, 2823 KiB

Open AccessArticle

Lu₃Al₅O₁₂:Ce³⁺ Fluorescent Ceramic with Deep Traps: Thermoluminescence and Photostimulable Luminescence Properties

by Junwei Zhang, Miao Zhao, Qiao Hu, Renjie Jiang, Hao Ruan and Hui Lin

Materials 2025, 18(1), 63; https://doi.org/10.3390/ma18010063 - 27 Dec 2024

Viewed by 590

Abstract

Electron-trapping materials have attracted a lot of attention in the field of optical data storage. However, the lack of suitable trap levels has hindered its development and application in the field of optical data storage. Herein, Lu₃Al₅O₁₂:Ce [...] Read more.

Electron-trapping materials have attracted a lot of attention in the field of optical data storage. However, the lack of suitable trap levels has hindered its development and application in the field of optical data storage. Herein, Lu₃Al₅O₁₂:Ce³⁺ fluorescent ceramics were developed as the optical storage medium, and high-temperature vacuum sintering induced the formation of deep traps (1.36 eV). The matrix based on the garnet-structured material ensures excellent rewritability. By analyzing the thermoluminescence and photostimulable luminescence, it is found that the transition of electrons provided by Ce³⁺ between the conduction band and trap levels offers the possibility for optical data storage. As evidence of its application, the optical information encoding using 254 nm light and decoding using a light stimulus and thermal stimulus were applied. These findings are expected to provide candidate material for novel optical storage technology, and further promote the development of advanced information storage technology. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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13 pages, 4036 KiB

Open AccessFeature PaperArticle

Improving Visible Light Photocatalysis Using Optical Defects in CoO_x-TiO₂ Photonic Crystals

by Alexia Toumazatou, Elias Sakellis and Vlassis Likodimos

Materials 2024, 17(23), 5996; https://doi.org/10.3390/ma17235996 - 7 Dec 2024

Viewed by 1202

Abstract

The rational design of photonic crystal photocatalysts has attracted significant interest in order to improve their light harvesting and photocatalytic performances. In this work, an advanced approach to enhance slow light propagation and visible light photocatalysis is demonstrated for the first time by [...] Read more.

The rational design of photonic crystal photocatalysts has attracted significant interest in order to improve their light harvesting and photocatalytic performances. In this work, an advanced approach to enhance slow light propagation and visible light photocatalysis is demonstrated for the first time by integrating a planar defect into CoO_x-TiO₂ inverse opals. Trilayer photonic crystal films were fabricated through the successive deposition of an inverse opal TiO₂ underlayer, a thin titania interlayer, and a photonic top layer, whose visible light activation was implemented through surface modification with CoO_x nanoscale complexes. Optical measurements showed the formation of “donor”-like localized states within the photonic band gap, which reduced the Bragg reflection and expanded the slow photon spectral range. The optimization of CoO_x loading and photonic band gap tuning resulted in a markedly improved photocatalytic performance for salicylic acid degradation and photocurrent generation compared to the additive effects of the constituent monolayers, indicative of light localization in the defect layer. The electrochemical impedance results showed reduced recombination kinetics, corroborating that the introduction of an optical defect into inverse opal photocatalysts provides a versatile and effective strategy for boosting the photonic amplification effects in visible light photocatalysis by evading the constraints imposed by narrow slow photon spectral regions. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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8 pages, 303 KiB

Open AccessArticle

Multiferroic and Phonon Properties of the Double Perovskite Pr₂FeAlO₆

by Angel T. Apostolov, Iliana N. Apostolova and Julia M. Wesselinowa

Materials 2024, 17(19), 4785; https://doi.org/10.3390/ma17194785 - 29 Sep 2024

Viewed by 858

Abstract

With the help of a microscopic model and Green’s function technique, we studied the multiferroic and phonon properties of the recently reported new multiferroic Pr₂FeAlO₆ (PFAO) compound, which belongs to the double perovskite A₂BB’O₆ family. The magnetization [...] Read more.

With the help of a microscopic model and Green’s function technique, we studied the multiferroic and phonon properties of the recently reported new multiferroic Pr₂FeAlO₆ (PFAO) compound, which belongs to the double perovskite A₂BB’O₆ family. The magnetization decreases with the increase in temperature and disappears at the ferromagnetic Curie temperature

T_{C}^{F M}

. The polarization increases with the application of an external magnetic field, indicating strong magnetoelectric coupling and confirming the multiferroic behavior of PFAO. In the curves of dependence of the phonon energy and their damping with respect to temperature, a kink is observed at

T_{C}^{F M}

. This is due to the strong anharmonic spin–phonon interactions, which play a crucial role below

T_{C}^{F M}

and are frequently observed in other double perovskite compounds. Above

T_{C}^{F M}

, only anharmonic phonon–phonon coupling remains. The phonon mode is controlled by an external magnetic field. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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8 pages, 2626 KiB

Open AccessEditor’s ChoiceArticle

Improvement of the Stability of Quantum-Dot Light Emitting Diodes Using Inorganic HfO_x Hole Transport Layer

by Jung Min Yun, Min Ho Park, Yu Bin Kim, Min Jung Choi, Seunghwan Kim, Yeonjin Yi, Soohyung Park and Seong Jun Kang

Materials 2024, 17(19), 4739; https://doi.org/10.3390/ma17194739 - 27 Sep 2024

Viewed by 1392

Abstract

One of the major challenges in QLED research is improving the stability of the devices. In this study, we fabricated all inorganic quantum-dot light emitting diodes (QLEDs) using hafnium oxide (HfO_x) as the hole transport layer (HTL), a material commonly used [...] Read more.

One of the major challenges in QLED research is improving the stability of the devices. In this study, we fabricated all inorganic quantum-dot light emitting diodes (QLEDs) using hafnium oxide (HfO_x) as the hole transport layer (HTL), a material commonly used for insulator. Oxygen vacancies in HfO_x create defect states below the Fermi level, providing a pathway for hole injection. The concentration of these oxygen vacancies can be controlled by the annealing temperature. We optimized the all-inorganic QLEDs with HfO_x as the HTL by changing the annealing temperature. The optimized QLEDs with HfO_x as the HTL showed a maximum luminance and current efficiency of 66,258 cd/m² and 9.7 cd/A, respectively. The fabricated all-inorganic QLEDs exhibited remarkable stability, particularly when compared to devices using organic materials for the HTL. Under extended storage in ambient conditions, the all-inorganic device demonstrated a significantly enhanced operating lifetime (T₅₀) of 5.5 h, which is 11 times longer than that of QLEDs using an organic HTL. These results indicate that the all-inorganic QLEDs structure, with ITO/MoO₃/HfO_x/QDs/ZnMgO/Al, exhibits superior stability compared to organic-inorganic hybrid QLEDs. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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16 pages, 8286 KiB

Open AccessFeature PaperArticle

A DFT Computational Study of Type-I Clathrates A₈Sn_46−x (A = Cs or NH₄, x = 0 or 2)

by Nikolaos Kelaidis, Emmanuel Klontzas and Andreas Kaltzoglou

Materials 2024, 17(18), 4595; https://doi.org/10.3390/ma17184595 - 19 Sep 2024

Viewed by 1314

Abstract

Semiconducting clathrates have attracted considerable interest in the field of thermoelectric materials. We report here a computational study on the crystal structure, the enthalpy of formation, and the physical properties of the following type-I clathrates: (a) experimentally studied Cs₈Sn₄₄ and [...] Read more.

Semiconducting clathrates have attracted considerable interest in the field of thermoelectric materials. We report here a computational study on the crystal structure, the enthalpy of formation, and the physical properties of the following type-I clathrates: (a) experimentally studied Cs₈Sn₄₄ and hypothetical Cs₈Sn₄₆ and (b) hypothetical (NH₄)₈Sn_46−x (x = 0 or 2). The ab initio VASP calculations for the nominal stoichiometries include the geometry optimization of the initial structural models, enthalpies of formation, and the electronic and phonon density of states. Comparison of the chemical bonding of the structural models is performed via the electron localization function. The results show that the presence and distribution of defects in the Sn framework for both Cs₈Sn_46−x and (NH₄)₈Sn_46−x systems significantly alters the formation energy and its electrical properties, ranging from metallic to semiconducting behavior. In particular, one defect per six-membered Sn ring in a 3D spiro-network is the thermodynamically preferred configuration that results in the Cs₈Sn₄₄ and (NH₄)₈Sn₄₄ stoichiometries with narrow-band gap semiconducting behavior. Moreover, the rotation of the ammonium cation in the polyhedral cavities is an interesting feature that may promote the use of ammonium or other small molecular cations as guests in clathrates for thermoelectric applications; this is due to the decrease in the lattice thermal conductivity. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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13 pages, 4081 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Raman Scattering in CVD-Grown MoS₂/Ag Nanoparticle Hybrids

by Dionysios M. Maratos, Antonios Michail, Alkeos Stamatelatos, Spyridon Grammatikopoulos, Dimitris Anestopoulos, Vassilis Tangoulis, Konstantinos Papagelis, John Parthenios and Panagiotis Poulopoulos

Materials 2024, 17(17), 4396; https://doi.org/10.3390/ma17174396 - 6 Sep 2024

Cited by 2 | Viewed by 1679

Abstract

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful, non-destructive technique for enhancing molecular spectra, first discovered in 1974. This study investigates the enhancement of Raman signals from single- and few-layer molybdenum disulfide (MoS₂) when interacting with silver nanoparticles. We synthesized a MoS [...] Read more.

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful, non-destructive technique for enhancing molecular spectra, first discovered in 1974. This study investigates the enhancement of Raman signals from single- and few-layer molybdenum disulfide (MoS₂) when interacting with silver nanoparticles. We synthesized a MoS₂ membrane primarily consisting of monolayers and bilayers through a wet chemical vapor deposition method using metal salts. The silver nanoparticles were either directly grown on the MoS₂ membrane or placed beneath it. Raman measurements revealed a significant increase in signal intensity from the MoS₂ membrane on the silver nanoparticles, attributed to localized surface plasmon resonances that facilitate SERS. Our results indicate that dichalcogenide/plasmonic systems have promising applications in the semiconductor industry. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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12 pages, 5681 KiB

Open AccessFeature PaperArticle

Thermal Relaxation in Janus Transition Metal Dichalcogenide Bilayers

by Aristotelis P. Sgouros, Fotios I. Michos, Michail M. Sigalas and George Kalosakas

Materials 2024, 17(17), 4200; https://doi.org/10.3390/ma17174200 - 25 Aug 2024

Viewed by 949

Abstract

In this work, we employ molecular dynamics simulations with semi-empirical interatomic potentials to explore heat dissipation in Janus transition metal dichalcogenides (JTMDs). The middle atomic layer is composed of either molybdenum (Mo) or tungsten (W) atoms, and the top and bottom atomic layers [...] Read more.

In this work, we employ molecular dynamics simulations with semi-empirical interatomic potentials to explore heat dissipation in Janus transition metal dichalcogenides (JTMDs). The middle atomic layer is composed of either molybdenum (Mo) or tungsten (W) atoms, and the top and bottom atomic layers consist of sulfur (S) and selenium (Se) atoms, respectively. Various nanomaterials have been investigated, including both pristine JTMDs and nanostructures incorporating inner triangular regions with a composition distinct from the outer bulk material. At the beginning of our simulations, a temperature gradient across the system is imposed by heating the central region to a high temperature while the surrounding area remains at room temperature. Once a steady state is reached, characterized by a constant energy flux, the temperature control in the central region is switched off. The heat attenuation is investigated by monitoring the characteristic relaxation time (τ_av) of the local temperature at the central region toward thermal equilibrium. We find that SMoSe JTMDs exhibit thermal attenuation similar to conventional TMDs (τ_av~10–15 ps). On the contrary, SWSe JTMDs feature relaxation times up to two times as high (τ_av~14–28 ps). Forming triangular lateral heterostructures in their surfaces leads to a significant slowdown in heat attenuation by up to about an order of magnitude (τ_av~100 ps). Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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16 pages, 2545 KiB

Open AccessArticle

Cavity-Tuned Exciton Dynamics in Transition Metal Dichalcogenides Monolayers

by Kaijun Shen, Kewei Sun, Maxim F. Gelin and Yang Zhao

Materials 2024, 17(16), 4127; https://doi.org/10.3390/ma17164127 - 20 Aug 2024

Cited by 2 | Viewed by 1339

Abstract

A fully quantum, numerically accurate methodology is presented for the simulation of the exciton dynamics and time-resolved fluorescence of cavity-tuned two-dimensional (2D) materials at finite temperatures. This approach was specifically applied to a monolayer WSe

_{2}

system. Our methodology enabled us to identify [...] Read more.

A fully quantum, numerically accurate methodology is presented for the simulation of the exciton dynamics and time-resolved fluorescence of cavity-tuned two-dimensional (2D) materials at finite temperatures. This approach was specifically applied to a monolayer WSe

_{2}

system. Our methodology enabled us to identify the dynamical and spectroscopic signatures of polaronic and polaritonic effects and to elucidate their characteristic timescales across a range of exciton–cavity couplings. The approach employed can be extended to simulation of various cavity-tuned 2D materials, specifically for exploring finite temperature nonlinear spectroscopic signals. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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18 pages, 7635 KiB

Open AccessArticle

A Novel Approach for Evaluating the Influence of Texture Intensities on the First Magnetization Curve and Hysteresis Loss in Fe–Si Alloys

by Daniele Carosi, Alessandro Morri, Lorella Ceschini and Alessandro Ferraiuolo

Materials 2024, 17(16), 3969; https://doi.org/10.3390/ma17163969 - 9 Aug 2024

Viewed by 1524

Abstract

This paper examines the relationship between the magnetization behavior and crystal lattice orientations of Fe–Si alloys intended for magnetic applications. A novel approach is introduced to assess anisotropy of the magnetic losses and first magnetization curves. This method links the magnetocrystalline anisotropy energy [...] Read more.

This paper examines the relationship between the magnetization behavior and crystal lattice orientations of Fe–Si alloys intended for magnetic applications. A novel approach is introduced to assess anisotropy of the magnetic losses and first magnetization curves. This method links the magnetocrystalline anisotropy energy of single crystal structures to the textures of polycrystalline materials through a vectorial space description of the crystal unit cell, incorporating vectors for external applied field and saturation magnetization. This study provides a preliminary understanding of how texture influences magnetic loss rates and the first magnetization curves. Experimental results from Electron Back-Scattered Diffraction (EBSD) and Single-Sheet Tests (SSTs), combined with energy considerations and mathematical modeling, reveal the following key findings: (i) a higher density of cubic texture components, whether aligned or rotated relative to the rolling direction, decreases magnetic anisotropy, suggesting that optimizing cubic texture can enhance material performance; (ii) at high magnetic fields, there is no straightforward correlation between energy losses and polarization; and (iii) magnetization rates significantly impact magnetization loss rates, highlighting the importance of considering these rates in optimizing Fe–Si sheet manufacturing processes. These findings offer valuable insights for improving the manufacturing and performance of Fe–Si sheets, emphasizing the need for further exploration of texture effects on magnetic behavior. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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11 pages, 4002 KiB

Open AccessArticle

Chalcogen Doping in SnO₂: A DFT Investigation of Optical and Electronic Properties for Enhanced Photocatalytic Applications

by Nikolaos Kelaidis, Yerassimos Panayiotatos and Alexander Chroneos

Materials 2024, 17(16), 3910; https://doi.org/10.3390/ma17163910 - 7 Aug 2024

Viewed by 1098

Abstract

Tin dioxide (SnO₂) is an important transparent conductive oxide (TCO), highly desirable for its use in various technologies due to its earth abundance and non-toxicity. It is studied for applications such as photocatalysis, energy harvesting, energy storage, LEDs, and photovoltaics as [...] Read more.

Tin dioxide (SnO₂) is an important transparent conductive oxide (TCO), highly desirable for its use in various technologies due to its earth abundance and non-toxicity. It is studied for applications such as photocatalysis, energy harvesting, energy storage, LEDs, and photovoltaics as an electron transport layer. Elemental doping has been an established method to tune its band gap, increase conductivity, passivate defects, etc. In this study, we apply density functional theory (DFT) calculations to examine the electronic and optical properties of SnO₂ when doped with members of the oxygen family, namely S, Se, and Te. By calculating defect formation energies, we find that S doping is energetically favourable in the oxygen substitutional position, whereas Se and Te prefer the Sn substitutional site. We show that S and Se substitutional doping leads to near gap states and can be an effective way to reduce the band gap, which results in an increased absorbance in the optical part of the spectrum, leading to improved photocatalytic activity, whereas Te doping results in several mid-gap states. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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9 pages, 446 KiB

Open AccessArticle

Theoretical Study of the Magnetic and Optical Properties of Ion-Doped LiMPO₄ (M = Fe, Ni, Co, Mn)

by Iliana N. Apostolova, Angel T. Apostolov and Julia Mihailowa Wesselinowa

Materials 2024, 17(9), 1945; https://doi.org/10.3390/ma17091945 - 23 Apr 2024

Cited by 3 | Viewed by 1023

Abstract

Using a microscopic model and Green’s function theory, we calculated the magnetization and band-gap energy in ion-doped LiMPO₄ (LMPO), where M = Fe, Ni, Co, Mn. Ion doping, such as with Nb, Ti, or Al ions at the [...] Read more.

Using a microscopic model and Green’s function theory, we calculated the magnetization and band-gap energy in ion-doped LiMPO₄ (LMPO), where M = Fe, Ni, Co, Mn. Ion doping, such as with Nb, Ti, or Al ions at the Li site, induces weak ferromagnetism in LiFePO₄. Substituting Li with ions of a smaller radius, such as Nb, Ti, or Al, creates compressive strain, resulting in increased exchange interaction constants and a decreased band-gap energy,

E_{g}

, in the doped material. Notably, Nb ion doping at the Fe site leads to a more pronounced decrease in

E_{g}

compared to doping at the Li site, potentially enhancing conductivity. Similar trends in

E_{g}

reduction are observed across other LMPO₄ compounds. Conversely, substituting ions with a larger ionic radius than Fe, such as Zn and Cd, causes an increase in

E_{g}

. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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Review

Jump to: Research

16 pages, 954 KiB

Open AccessReview

Dynamical Projective Operatorial Approach (DPOA): Theory and Applications to Pump–Probe Setups and Semiconductors

by Amir Eskandari-asl and Adolfo Avella

Materials 2025, 18(6), 1310; https://doi.org/10.3390/ma18061310 - 16 Mar 2025

Viewed by 342

Abstract

This manuscript reviews our recently developed theory, the dynamical projective operatorial approach (DPOA), for studying pump–probe setups in ultra-fast regimes. After reviewing the general formulation of the DPOA, we focus on its lattice version and provide a formalism that is particularly suitable for [...] Read more.

This manuscript reviews our recently developed theory, the dynamical projective operatorial approach (DPOA), for studying pump–probe setups in ultra-fast regimes. After reviewing the general formulation of the DPOA, we focus on its lattice version and provide a formalism that is particularly suitable for several pumped semiconductors. Within the DPOA, we also compute the TR-ARPES signal through out-of-equilibrium Green’s functions and establish an out-of-equilibrium counterpart of the fluctuation–dissipation theorem. Moreover, we generalize the linear response theory to pumped systems and address, within the DPOA, the differential transient optical properties, providing an overall robust theoretical and computational framework for studying pump–probe setups. Considering a minimal model for a semiconductor, we illustrate the capabilities of the DPOA and discuss several features emerging in this case study that are relevant to real materials. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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25 pages, 8173 KiB

Open AccessReview

Advances in Powder-Filled Mold Processes: A Comprehensive Review and Outlook

by Pengyu Bai, Shuhua Yang, Yalin Yan, Dongliang Wang and Yanwei Ma

Materials 2024, 17(22), 5476; https://doi.org/10.3390/ma17225476 - 9 Nov 2024

Viewed by 1485

Abstract

Powder molding technology is a versatile process widely used in the pharmaceutical, ceramic, chemical, food, and powder metallurgy industries. The powder-filling mold process is a key link in powder compression molding, and the uniformity and consistency of powder filling directly affect the final [...] Read more.

Powder molding technology is a versatile process widely used in the pharmaceutical, ceramic, chemical, food, and powder metallurgy industries. The powder-filling mold process is a key link in powder compression molding, and the uniformity and consistency of powder filling directly affect the final quality of powder products. Powder filling of molds is a more complex flow process. This paper first reviews the methods used to test powder flow characteristics and comments on their applicability to the mold-filling process, provides an in-depth discussion of four different filling techniques, focusing on the flow behavior of the powder during the filling process, and analyzes the effects of powder characteristics and process parameters on the filling effect. By reviewing the latest advances and identifying the key challenges, a valuable reference is provided for the mold-filling process. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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