Article
Chemistry, Physical
Xingyue Zhangyang, Lei Liu, Feifei Lu, Jian Tian
Summary: First-principles calculations based on density functional theory were used to investigate the electronic and optical properties of composition-tunable InxGa1-xN bulks and nanowires. The studies found that increasing the In composition reduces the stability of InxGa1-xN nanowires, while increasing the nanowire diameter improves stability. Additionally, the band gap of InxGa1-xN nanowires narrows and the intrinsic absorption spectrum is red-shifted with increasing In composition.
APPLIED SURFACE SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
O. de Melo, M. Ramirez-Lopez, M. Perez-Caro, S. Gallardo-Hernandez, Y. L. Casallas-Moreno, M. Sanchez, J. Ortega, G. Santana, M. Behar, Y. Gonzalez, M. Lopez-Lopez
Summary: In this study, self-assembling of InxGa1-xN nanostructures under strong nitrogen-rich conditions on Si (111) substrates by molecular beam epitaxy was reported. The strain evolution and morphological changes of the films were monitored using in-situ analysis. Different nanostructures were observed depending on the In content, including nanocolumns and nanowalls. XRD and RBS measurements provided information about the indium concentration and composition of the films, and suggested phase separation at higher indium concentration. The morphology change from columnar surface arrangement to separated nanowalls as the indium content increases was discussed. A shift towards lower energies of the low temperature photoluminescence spectra with increased In concentration was observed.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2022)
Article
Physics, Applied
M. Katsikini, K. Filintoglou, F. Pinakidou, N. Pliatsikas, J. Arvanitidis, D. Christofilos, E. C. Paloura, S. Ves, U. Reinholz, E. Papadomanolaki, E. Iliopoulos
Summary: This study combines In-K-edge x-ray absorption fine structure (EXAFS), x-ray photoelectron, and Raman spectroscopy to comprehensively investigate InxGa1-xN layers with energy gaps covering nearly the entire visible spectrum. The research focuses on deriving the ionicity of In-N bonds, phonon frequency dependence, and phonon confinement due to alloying-induced perturbations in the periodic potential.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Condensed Matter
F. Sonmez, S. Ardali, B. Arpapay, E. Tiras
Summary: The photoluminescence properties of InGaN/GaN multiple quantum wells with different quantum well numbers were studied in this research. The observed shift in the peak energy of photoluminescence with increasing temperature is explained by the S-shaped behavior. The localization states of carriers and the inhomogeneity in the samples contribute to this behavior. The study also discusses the parameters that characterize the degree of carrier localization and the activation energy.
PHYSICA B-CONDENSED MATTER
(2022)
Article
Materials Science, Multidisciplinary
Chumpol Supatutkul, Kedkanok Sitarachu, Yongyut Laosiritaworn, Atchara Punya Jaroenjittichai
Summary: This study presents a detailed understanding of the electronic structures of lead-free halide double perovskites Cs2B+B3+Br6 and their potential applications in photovoltaics and optoelectronics. The calculated band structures and effective masses of Cs2B+B3+Br6 indicate that they have bandgaps covering a wide range of the spectrum, as well as qualified electrical conductivity due to their small effective masses. These findings will inspire further synthesis and characterization of Cs2B+B3+Br6 and related materials.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Xuewen Wang, Yanbo Zhao, Haiting Bai, Yuanmeng Zhang, Jie Gao, Chunxue Zhai, Yang Dai
Summary: This paper investigates the electronic structures and optical properties of monolayer InxAl1-xN with different compositions using the HSE function and GGA-PBE function respectively. The influence of electronic structure on properties and the effect of doping quantity on characteristics are analyzed, revealing a trend in the complex dielectric function and absorption spectrum. The results show that as x increases, the static dielectric constant, electron transition ability, and absorption peak intensity in the light absorption spectrum also increase. Therefore, the InxAl1-xN compound can theoretically achieve adjustable energy gap and photoelectric performance by varying x, making it suitable for various optoelectronic devices including solar cells and sensors.
MATERIALS SCIENCE-MEDZIAGOTYRA
(2022)
Article
Physics, Multidisciplinary
T. M. Inerbaev, T. Matsuoka, Y. Kawazoe
Summary: This study successfully estimates the band gap value in InxGa1-xN alloys through density functional calculations combined with subsequent GW calculations, and the results are in good agreement with experimental results. It is found that the LDA and GW(0) methods provide satisfactory theoretical results for the electronic structure calculation in this alloy system.
BULLETIN OF THE UNIVERSITY OF KARAGANDA-PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Hongjing Cui, Ning Liu, Rulong Zhou, Dongdong Li, Jigui Cheng
Summary: By investigating the structures and elastic properties of ternary W-Ta-V alloys, it was found that the elastic properties generally decrease with the addition of Ta and V, but the ductility of W is effectively improved. Electronic structure analysis showed that alloying Ta and V enhances the metallicity of W, and the types and strength of bonds influence the stability and elastic modulus of the alloys.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Nuclear Science & Technology
Diyou Jiang, Wenbo Xiao, Desheng Liu, Sanqiu Liu
Summary: The study shows that W-Re alloys are thermodynamically stable, but the thermodynamic stability of W8Re8 alloy is poor. Except for W14Re2 alloy, the mechanical strength of W-Re alloys is lower than that of pure tungsten, but the B/G ratio and Poisson's ratio of W-Re alloys are higher than that of pure W, indicating that Re alloying can effectively improve the ductility of pure W.
FUSION ENGINEERING AND DESIGN
(2021)
Article
Chemistry, Multidisciplinary
Giancarlo Cappellini, Andrea Bosin, Giovanni Serra, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Article
Materials Science, Multidisciplinary
Jens Rene Suckert, Claudia Roedl, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Summary: The study shows that band inversion in hexagonal germanium can be achieved through strain, transitioning from a pseudo-direct band gap to a direct band gap, with moderate tensile uniaxial strain showing the potential to achieve this goal.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Physics, Condensed Matter
Filipe Matusalem, Friedhelm Bechstedt, Ivan Guilhon, Marcelo Marques, Lara K. Teles
Summary: A computationally efficient methodology for calculating Z(2) topological invariants is presented and applied to group-IV graphene-like systems, showing the importance of quasiparticle (QP) effects in predicting the topological or trivial character.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Multidisciplinary
Jakob Genser, Daniele Nazzari, Viktoria Ritter, Ole Bethge, Kenji Watanabe, Takashi Taniguchi, Emmerich Bertagnolli, Friedhelm Bechstedt, Alois Lugstein
Summary: Silicene shows promising potential for high-performance devices due to its unique electronic and optical properties, but its outstanding characteristics are not preserved on certain growth templates.
Article
Materials Science, Multidisciplinary
Abderrezak Belabbes, Friedhelm Bechstedt, Silvana Botti
Summary: By conducting ab initio calculations, it has been demonstrated that perturbed hexagonal germanium is an excellent material for active optoelectronic devices in the infrared region. Perturbing the system through atomic substitution and applying strain can greatly enhance the oscillator strength and energy transition of the material, making it suitable for light emitting devices.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Pedro Borlido, Jens Rene Suckert, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti, Claudia Roedl
Summary: Ab initio calculations were performed to study the electronic and optical properties of hexagonal SiGe alloys. It was found that alloying can enhance the optical transitions of hexagonal Ge, making the alloys efficient optical emitters for integrated optoelectronic applications.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Pedro Borlido, Friedhelm Bechstedt, Silvana Botti, Claudia Roedl
Summary: Ge-rich hexagonal SiGe alloys have emerged as new direct-gap semiconductors with potential for integration of photonics on silicon. Optical, transport, and thermoelectric properties of these alloys were investigated using first-principles methods. The alloy band gap remains direct below 45% Si content and optical spectra show tunability with composition. Transport coefficients exhibit similar behaviors in cubic and hexagonal alloys, but the latter display anisotropic response due to reduced symmetry. The Seffbeck coefficients and thermoelectric power factors show nonmonotonous variations with Si content regardless of temperature.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Mousa Bejani, Olivia Pulci, Naser Karimi, Elena Cannuccia, Friedhelm Bechstedt
Summary: In this study, we conducted a detailed analysis of the electronic properties and lattice dynamics of different layers of beta-InSe through theoretical calculations. We found that the few-layers systems are indirect band gap semiconductors with a Mexican-hat-shaped top valence band. The phonon analysis revealed the dynamical stability of mono- and bi-layers, as well as the breakdown of the longitudinal-optical-transverse-optical splitting with an increase to four layers. The Raman and IR spectra were dominated by in-plane and out-of-plane lattice vibrations, and small shifts of the peak positions and variations of the peak intensities were observed as signatures of the number of layers.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Multidisciplinary Sciences
Giancarlo Cappellini, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Summary: We conducted a systematic investigation on the electronic and optical properties of two crystals of alkaline earth metal fluorides using state-of-the-art techniques. The calculations were performed using density functional theory, many-body perturbation theory, and the Bethe-Salpeter equation. Our results showed distinctive properties for rutile MgF2 compared to cubic SrF2 and other members of the alkaline earth metal fluoride family. The excitonic effects in finite-sized systems were confirmed through a comparison between bulk and cluster calculations.
Article
Materials Science, Multidisciplinary
Martin Keller, Abderrezak Belabbes, Juergen Furthmueller, Friedhelm Bechstedt, Silvana Botti
Summary: In this paper, the energetic, structural, elastic, and electronic properties of hexagonal SiGe are analyzed using density functional theory. The phase diagram shows that the diamond structure is the most stable, but hexagonal modifications are close to the phase boundary. Band structure calculations predict significant changes in electronic states with hexagonality. Si is always a semiconductor with indirect band gaps, while the hexagonal Ge polytypes have direct band gaps. Band alignment based on the branch-point energy leads to type-I heterocrystalline interfaces between Ge polytypes.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Alessia Muroni, Simone Brozzesi, Friedhelm Bechstedt, Paola Gori, Olivia Pulci
Summary: We conducted a comprehensive study on the structural and electronic properties of a graphene/phosphorene heterostructure using density functional theory. We found that by optimizing the lattice constants, the in-plane strain of the heterostructure can be reduced to under 1%. The presence of weak van der Waals interaction between the graphene and phosphorene layers was confirmed. Additionally, we demonstrated that G/P heterostructures can form both n-type and p-type Schottky contacts under external perturbations, suggesting their potential for novel electronics applications and optoelectronic devices.
Article
Materials Science, Multidisciplinary
Abderrezak Belabbes, Silvana Botti, Friedhelm Bechstedt
Summary: This study investigates the natural and true band profiles at heterojunctions formed by hexagonal SixGe1-x alloys. The findings show that the natural band offsets are not significantly affected by different alignment methods or functional choices. Ge-rich alloys exhibit a type-I heterocharacter with direct band gaps, while Si-rich junctions are type-I but with an indirect band gap. The true band lineups at pseudomorphically grown heterostructures are strongly influenced by the biaxial strain generated in the adjacent alloys.
Proceedings Paper
Engineering, Electrical & Electronic
E. M. T. Fadaly, A. Dijkstra, J. R. Suckert, D. Ziss, M. A. J. Tilburg, C. Mao, Y. Ren, V. T. V. Lange, S. Koling, M. A. Verheijen, D. Busse, C. Rodl, J. Furthmuller, F. Bechstedt, J. Stangl, J. J. Finley, S. Botti, J. E. M. Haverkort, E. P. A. M. Bakkers
Summary: The study found that a direct band gap can be created in Si1-xGex alloys by changing the crystal structure from cubic to hexagonal, offering new possibilities for the application of opto-electronic devices.
2021 SILICON NANOELECTRONICS WORKSHOP (SNW)
(2021)
Article
Materials Science, Multidisciplinary
Friedhelm Bechstedt, Simone Grillo, Olivia Pulci, Paola Gori
Summary: The thermal properties and electrical conductance of 2D electron gases in doped Xenes were studied using a four-band model, taking into account spin-orbit interactions and the influence of an electric field. The results showed that the thermal conductance of Xenes increases linearly or quadratically with temperature, with only small variations in electrical conductance, except for plumbene. In addition, for 2D electron gases with nearly Dirac character, the ratio of electron thermal conductance to electric conductance depends on doping level and temperature.