| 1. |
- Alinejadian, Navid, et al.
(författare)
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Progress in additive manufacturing of MoS2-based structures for energy storage applications - A review
- 2022
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 139
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Forskningsöversikt (refereegranskat)abstract
- Investigation of next-generation manufacturing methods for the processing of functional materials and offering products with improved performance/functionalities has always been a challenge in terms of energy efficiency, cost-effectiveness, and eco-friendliness. Additive manufacturing (AM) attributes to rapid prototyping techniques that provide new opportunities to test new concepts and design complex 3D structures from metals, ceramics, and composites. Moreover, as a well-known transition metal dichalcogenide, Molybdenum disulfide (MoS2) is a two-dimensional (2D) material with outstanding electrochemical, physical, and mechanical properties that make it a potential candidate for energy storage electrodes via intercalation of different H+, Li+, Na+, and K+ cations. In this review, we discuss the existing conventional MoS2-processing methodologies and compare them with the novel additive manufacturing processes (especially laser-based powder bed fusion). The authors are convinced that the processing of prominent MoS2-based functional structures by the novel additive manufacturing processes can provide complex structures for different electrochemical applications, particularly for energy conversion/ storage systems.
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| 2. |
- Allal, Adel, et al.
(författare)
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A comparative theoretical investigation of optoelectronic and mechanical properties of KYS2 and KLaS2
- 2020
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 113
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Tidskriftsartikel (refereegranskat)abstract
- The ternary sulfides KYS2 and KLaS2 are two promising candidates for numerous applications, as much as white LED, X-ray phosphor and transparent conductor materials. However, theoretical studies on these materials are lacking, and many of their physical properties are still unknown. The aim of this work is to investigate the physical properties of the ternary sulfides KYS2 and KLaS2 namely, structural, elastic, optoelectronic, thermodynamic analysis, and set the substitution effect of Y and La elements in the two compounds. The fundamental properties calculations are based on ab-initio pseudopotential framework, with both local density approximation (LDA) and generalized gradient approximations (GGA) along with an expanded set of plane waves. The Becke, 3-parameter, Lee–Yang–Parr (B3LYP) hybrid functional is also employed to describe the electronic structures and optical properties. The optimized crystal parameters are correlated very well with the existing experimental data. The predicted values of the elastic constants demonstrate that the two compounds are mechanically stable and can be classified as brittle materials. The band structure analysis reveals that both KYS2 and KLaS2 have indirect band gap. The optical properties, like the refractive index, extinction, absorption and reflectivity coefficients, are determined for various polarizations of incident light, while both compounds present optical anisotropy. The obtained optical properties indicate the high transparency of KYS2 and KLaS2 in the infrared and visible regions, which makes them promising candidates for many of transparent applications. The thermodynamic properties are investigated with the help of quasiharmonic Debye model approximation. KYS2 has a larger bulk modulus value, which make it more beneficial in engineering applications. Calculations of thermodynamical properties indicate that KYS2 compound has better thermal conductivity, stronger chemical bonds and bigger hardness.
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| 3. |
- Allal, Adel, et al.
(författare)
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Phase stability, phonon, electronic, and optical properties of not-yet-synthesized CsScS2, CsYS2, and APmS(2) (A= Li, Na, K, Rb, Cs) materials : Insights from first-principles calculations
- 2022
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Transparent conducting materials (TCMs) combine two exclusive properties, electrical conductivity and visible light transparency; which make them a unique class of materials. They are required in a wide range of applications in modern life ranging from touchscreen-based devices, flat panel displays, light-emitting diodes (LED), and solar cells. Most of the commercially and widely used TCMs are n-type, whereas the development of highperformance p-type TCMs remains an outstanding challenge in the actual time. Herein, using the newly developed SCAN meta-GGA and the hybrid HSE06 functionals, we have explored the structural stability and physical properties of not-yet-synthesized ternary materials CsScS2, CsYS2, and APmS(2) (A = Li, Na, K, Rb, Cs) to identify promising p-type TCMs. As result, the calculated formation energy, phase diagram and phonon dispersion curves confirm that these materials are thermodynamically stable and feasible to synthesize experimentally. All these materials, have large optical band gaps (larger than 3.4 eV), small hole effective masses (except for LiPmS2), and have no absorption and weak reflectivity of the visible light. Our work demonstrates that these compounds have suitable properties for p-type TCMs applications.
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| 4. |
- Bathen, Marianne Etzelmueller, et al.
(författare)
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Dual configuration of shallow acceptor levels in 4H-SiC
- 2024
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Ingår i: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 177
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Tidskriftsartikel (refereegranskat)abstract
- Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor impurities at hexagonal and pseudo -cubic lattice sites in 4H-SiC, and tentatively assign the X peak to Al based on experimental findings and density functional theory calculations.
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| 5. |
- Ekström, Mattias, et al.
(författare)
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Self-aligned contacts to ion implanted S/D regions in 4H-SiC
- 2023
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier Ltd. - 1369-8001 .- 1873-4081. ; 168
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Tidskriftsartikel (refereegranskat)abstract
- The self-aligned silicide (salicide) process, where a metallic silicide is formed without lithographic definition to both source/drain-regions and the gate, is important for devices thanks to its ability to minimize parasitic resistances in scaled silicon CMOS technology. The challenge to transfer the process to SiC technology is two-fold: a single silicide has to give low resistance contacts to both ion implanted p-type and n-type simultaneously, and the typical temperatures required to form contacts to SiC is high enough that silicide agglomerates on polysilicon. In this work, we investigated if there exists a process window for salicide process for the purpose of developing a salicide process for SiC CMOS. Transfer length method structures were fabricated by ion implantation of phosphorus and aluminum to investigate simultaneous contacts to SiC. Bridge resistor structures (2μm width) were fabricated both with and without silicide-block to determine the silicide stability on highly in-situ doped polysilicon. The approach is design of experiment with multiple factors, including silicide composition, annealing temperature, deposited metal thickness and annealing time. The formation of self-aligned low resistive contacts to both n-type and p-type SiC was successful. The mutual process window for the co-existence of stable silicide on polysilicon and low resistive contacts to SiC, which is required for true salicide process, could not be found.
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| 6. |
- El Jamal, Ghada, et al.
(författare)
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A scalable, resource-efficient process for synthesis of self-supporting germanium nanomembranes
- 2024
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 172
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Tidskriftsartikel (refereegranskat)abstract
- The design of self-supporting membranes is gaining high interest in a broad range of applications, from nanodevices, optoelectronics, sensing, separation, and catalysis. In this report, we demonstrate a synthesis pathway for high quality ultrathin self-supporting germanium membranes using a highly scalable and resource-efficient process. We discuss the process flow, the compatibility between the materials and the processing chemicals, the important details for achieving the pure membranes and potential anomalies related to the etching process. Comprehensive characterization using SEM, EDX, TEM and nuclear microprobe analysis is employed for revealing the physical and structural properties of the synthesized membranes. The outcome of the fabrication process is large-area Ge nanomembranes with extremely flat and clean surfaces.
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| 7. |
- Lo, Yi-Ling, et al.
(författare)
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Determination of effective Ga/N ratio to control GaN growth behavior in liquid-target reactive magnetron sputter epitaxy
- 2024
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Ingår i: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- The optimization of magnetron sputter epitaxy (MSE) for the high -volume production of high -quality GaN films is increasingly important. This study concerns the influence of key MSE process parameters - including the partial pressure of process gas, target -to -substrate distance (TSD), and growth temperature (TG) - for the synthesis of GaN thin films using a liquid Ga target. It is observed that the effective Ga/N ratio on the substrate surface determines the film's growth behavior and affects material's composition and luminescence properties. A lower Ar/N2 partial pressure ratio substantially enhances the crystalline quality, evidenced by the reduction in peak width of x-ray rocking curves from approximately 1.25 degrees (N -rich regime) to 0.35 degrees (Ga-rich regime) and improved GaN bandgap emission. While target sputtered in a highly Ga-rich condition significantly reduces the GaN growth rate (R), primarily due to Ga desorption in nitrogen -limited condition at elevated TG. Ion mass spectrometry and rate monitor measurements demonstrate that the Ga/N ratio can be controlled by adjusting Ar/N2 pressure ratio in MSE process. A reduction in TSD from 9.3 cm to 7 cm resulted in an increased R from 541 nm/h to 731 nm/h, corroborated by Simulation of Metal Transport (SIMTRA) analysis. Temperature -dependent studies revealed that films grown above 900 degrees C exhibited flat surface with high crystalline quality.
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| 8. |
- Mustafa, Ghulam M., et al.
(författare)
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Study of optoelectronic and transport properties of MgLu2Z4 (Z=S, Se) spinels for optoelectronic and energy harvesting applications
- 2021
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 121
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Tidskriftsartikel (refereegranskat)abstract
- Intense research has been done to build materials that are potential candidates for energy storage applications. Spinels are of great interest in this respect because they have vast potential to be used in Mg-based batteries. To explore their energy storage as well as transport response, we calculate Mg-based spinels, namely MgLu2Z4 (ZS, Se). The full potential linearized augmented plane wave method has been used to examine their optoelectronic and transport response. An increase in the lattice constant has been observed by replacing S with Se, and our calculated values are in good agreement with those obtained experimentally. The Tran-Blaha modified Becke-Johnson exchange potential (TB-mBJ), has been used to study the optoelectronic and thermoelectric characteristics of the respective spinels. The dependence of these properties on the bandgap has also been observed. Replacing S with Se resulted in the transformation of the electronic bandgap from near-infrared to the visible region (MgLu2S4: 2.60 eV and MgLu2Se4: 2.00 eV). These results showed that these materials have the potential to be used in optoelectronic devices. The optical properties are discussed as a function of energy. Besides, the thermal transports are discussed with the help of Seebeck coefficient and figure of merit as a function of chemical potential and temperature.
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| 9. |
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| 10. |
- Siddiqui, Amna, et al.
(författare)
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Carrier removal rates in 4H–SiC power diodes : A predictive analytical model
- 2023
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 167
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model for predicting the proton and neutron radiation-induced carrier removal in silicon carbide (4H–SiC) diodes, is developed. It is primarily aimed towards a fast calculation of the carrier removal rates (ηe) and critical fluence (above which the diode drift layer is fully compensated), for a wide range of particle energies and diode ratings. The model utilizes the NIEL (non-ionizing energy loss) concept along with the actual carrier removal rate values for SiC available in the literature. A comparison to Si power devices is also made. The results from the predictive model suggest that diodes with a lower voltage rating can sustain a higher particle fluence and displacement damage before their drift layers are fully compensated. This provides radiation hardening guidelines for 4H–SiC power diodes at a device engineering level, which can help improve the reliability of circuits in harsh environment applications, such as space. The model is validated through TCAD simulations incorporating the proton-induced defects, as well as experimentally by irradiating SiC diodes with 2 MeV protons. The extracted compensation levels are in good agreement with those predicted by the analytical model, validating its potential in predicting carrier removal rate of SiC diodes for radiation prone environments.
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