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Hole-doped 2D InSe for spintronic applications
摘要： Using first-principles calculations based on density functional theory, we study the magnetic and electronic properties of hole-doped two-dimensional InSe. Our simulations reveal that although 2D InSe is intrinsically non-magnetic, a stable ferromagnetic phase appears for a wide range of hole densities. Interestingly, hole doping not only induces spontaneous magnetization but also half-metallicity, and hole-doped InSe, presenting one conducting and one insulating spin channel, could be highly promising for next generation spintronic nanodevices. The possibility to induce hole doping and a subsequent ferromagnetic order by intrinsic and extrinsic defects was also investigated. We found that In vacancy creates spin-polarized states close to the valence band and leads to a p-type behavior. Similar to In vacancies, group-V atoms replacing Se atoms lead to a p-type behavior, potentially stabilizing a ferromagnetic order in 2D InSe.
关键词： ferromagnetism,InSe,half-metallicity,hole-doping,defects
更新于2025-09-23 15:21:01
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Role of co-doping on structural, optical and magnetic properties of nano-crystalline ZnO thin films
摘要： This paper refers to investigation of structure, surface morphology, optical parameters and magnetic characteristics of the prepared ZnO thin films when Co concentration varies from 1 to 5 at wt %. X-ray diffraction study revealed that deposited films were poly-crystalline with hexagonal wurtzite structure. The band gap energy was calculated by using the envelope method. It’s value was decreased from 3.334 to 3.22 eV with increasing Co concentration up to 4 at wt % and then increased to 3.335 eV for 5 at wt% Co. The magnetic study indicated a ferromagnetic trend for all thin films. An oxygen vacancies–related F-center is a possible physical mechanism for generation of ferromagnetism. Scanning Electron Microscopy exhibited rough and porous morphology.
关键词： sol-gel,Thin films,ZnO,Ferromagnetism,doping
更新于2025-09-23 15:21:01
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Valley polarization reversal and spin ferromagnetism and antiferromagnetism in quantum dots of the topological insulator monolayer bismuthene on SiC
摘要： The valley and spin polarizations associated with electronic transport in quantum dots of the large-gap topological insulator (TI) monolayer bismuthene on SiC are investigated in the linear response regime using a minimal tight-binding model that accurately describes the low-energy electronic band structure of this TI. It is found that for zigzag edges the electronic edge states are strongly valley polarized if the Fermi energy lies in the bulk energy band gap. We predict the edge-state valley polarizations to switch between valleys K and K (cid:2) as the Fermi energy varies from the top of the valence band to the bottom of the conduction band or if the direction of electric current through the dot is reversed. If the electrostatic potential in the dot is nonuniform, we predict that the valley polarization of an electron can reverse as it travels through the dot. The valley polarization reversal is due to the zigzag edge-state dispersion crossing the center of the Brillouin zone that separates valleys K and K (cid:2) and is therefore predicted to be a general phenomenon. Although the spin polarization within the edge states is ferromagnetic, as expected for spin Hall devices, our calculations reveal the out-of-plane component of the spin polarization of the bulk valence band scattering states to be antiferromagnetic, and the direction of the out-of-plane component of the Neel vector to depend on whether the electronic accumulation belongs primarily to valley K or K (cid:2).
关键词： quantum dots,ferromagnetism,bismuthene,topological insulator,spin polarization,antiferromagnetism,SiC,tight-binding model,valley polarization
更新于2025-09-23 15:19:57
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Surface ferromagnetism in ZnO single crystal
摘要： We report on the room temperature surface ferromagnetism in undoped ZnO bulk single crystal. Typical ferromagnetic saturation behavior is clearly demonstrated by magnetization loops, and the saturated magnetization can be manipulated by annealing under argon atmosphere. A strongly correlation, between the saturated magnetization and the concentration of singly occupied oxygen vacancies on the surface of ZnO single crystal, is established by means of the Raman spectra, photoluminescence, electron paramagnetic resonance and atomic force microscope. It is suggested that the observed room temperature ferromagnetism in ZnO single crystal should be attributed to the effect of surface oxygen vacancy defects. This finding may help to get further insight into the ferromagnetic origin in other undoped oxide semiconductor materials.
关键词： D. Annealing,A. ZnO single crystal,C. Oxygen vacancies,B. Surface ferromagnetism
更新于2025-09-19 17:15:36
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Ge <sub/>x</sub> Si <sub/>1-x</sub> Virtual-Layer Enhanced Ferromagnetism in Self-assembled Mn <sub/>0.06</sub> Ge <sub/>0.94</sub> Quantum Dots Grown on Si Wafers by Molecular Beam Epitaxy
摘要： The self-assembled Mn0.06Ge0.94 quantum dots (QDs) on Si substrate or GexSi1-x virtual substrate (VS) were grown by molecular beam epitaxy. The GexSi1-x VS of different thicknesses and Ge compositions x were utilized to modulate the ferromagnetic properties of the above QDs. The MnGe QDs on GexSi1-x VS show a significant enhanced-ferromagnetism with a Curie temperature above 220 K. On the basis of the microstructural and magnetization results, the ferromagnetic properties of the QDs on GexSi1-x VS are believed to come from the intrinsic MnGe ferromagnetic phase rather than any intermetallic ferromagnetic compounds of Mn and Ge. At the same time, we found that by increasing Ge composition x of GexSi1-x VS, the ferromagnetism of QDs grown on VS will markedly increase due to the improvements of hole concentration and Ge composition inside the QDs. These results are fundamentally important in the understanding and especially to the realization of high Curie temperature MnGe diluted magnetic semiconductors.
关键词： ferromagnetism,molecular beam epitaxy,diluted magnetic semiconductors,GexSi1-x virtual substrate,MnGe quantum dots
更新于2025-09-19 17:13:59
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Room temperature ferromagnetism in ball milled Cu-doped ZnO nanocrystallines: an experimental and first-principles DFT studies
摘要： Experimental and theoretical studies on the room temperature ferromagnetism of ball milled Zn0.95Cu0.05O nanocrystalline, were reported. X-ray diffraction analysis reveals that the most dominant crystalline phase is hexagonal wurtzite with presence of weak peaks due to Cu and CuO. Rietveld analysis indicated that the crystallite size decreases with increasing milling time, while the strain enhanced with milling time. Magnetic measurements using SQUID expose remarkable room temperature ferromagnetic ordering for milled samples. The physical origin of the ferromagnetism order has been explained using a bound magnetic polaron model. Theoretical calculations based on First principles methods were employed to calculate the electronic structures and magnetic properties of Cu doping and zinc and oxygen vacancies behavior of Zn1?xCuxO. It was found that a Cu dopant leads to induce magnetism and exhibits an increasing of magnetic moment when Zn vacancy are introduced.
关键词： Room temperature ferromagnetism,Ball milled Cu-doped ZnO,Magnetic properties,Nanocrystalline,First-principles DFT
更新于2025-09-19 17:13:59
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Oxygen vacancy induced ferromagnetism in ball milled Zn0.97Ni0.03O: Confirmation through electron spin resonance
摘要： Among the semiconducting materials, ZnO is a versatile multifunctional candidate with a direct band gap of 3.37 eV at 300 K and large excitonic binding energy of 60 meV which can be useful for spintronics device applications. ZnO has high solubility for transition metals. The transition metals which have been used for DMS, Ni is the most efficient doping element to improve the electrical, magnetic properties of ZnO. Ni doped ZnO would be a good candidate to achieve ferromagnetic property with a high curie temperature i.e. above the room temperature. In this study, Zn1?xNixO (x = 0.03) powder sample was successfully synthesized by a ball milling technique. The X-ray diffraction analysis confirms the polycrystalline, hexagonal wurzite structure for 3% Ni doped ZnO nanoparticles. The substitution of Ni in the ZnO matrix has been confirmed by micro-Raman analysis with the observation of E2 (High) vibrational mode at 437 cm?1 which refers to the strongest mode of vibration in wurtzite crystal structure. A broadened peak observed at 570 cm?1 informs about the presence of clusters of oxygen vacancies. VSM measurement of the sample shows the ferromagnetic hysteresis loop at room temperature with saturation moment of 9 × 10?5 emu/g. The calculated ‘g’ value of 1.95 from electron spin resonance spectrum suggests that the observed ferromagnetism is due to the oxygen vacancy.
关键词： Diluted magnetic semiconductor,Electron spin resonance,Defects,Ferromagnetism,ZnO,Nanoparticles
更新于2025-09-19 17:13:59
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Colloidal Seconda??Neara??infrareda??emitting Mna??doped Ag2S Quantum Dots
摘要： Incorporation of transition metal dopants within a semiconductor nanocrystal has a tremendous effect on the optical and magnetic properties of the semiconductor nanocrystals. Herein, we showed the novel synthesis of second-near-infrared-emitting photoluminescent Mn2+-doped Ag2S quantum dots via co-pyrolysis of silver and manganese single source precursors. The Mn2+ doping level was flexibly tuned in Ag2S quantum dots, which was confirmed by elemental analysis and electron paramagnetic resonance spectroscopy. The Mn2+ doping induced negligible change in the pristine monoclinic acanthite Ag2S crystal structure but significantly decreased the photoluminescent intensity. Mn2+ doped Ag2S QDs exhibit the second-near-infrared-emission and ferromagnetic ordering, which show potential applicability for multimodal fluorescence/MRI probes.
关键词： Second Near-infrared,Manganese Dopant,Ferromagnetism,Quantum Dot,Silver Sulfide
更新于2025-09-16 10:30:52
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Ferromagnetism in quantum dot plaquettes
摘要： Following recent experimental progress concerning Nagaoka ferromagnetism in finite-size quantum dot plaquettes, a general theoretical analysis is warranted in order to ascertain in rather generic terms which arrangements of a small number of quantum dots can produce saturated ferromagnetic ground states and under which constraints on interaction and interdot tunneling in the plaquette. This is particularly necessary since Nagaoka ferromagnetism is fragile and arises only under rather special conditions. We test the robustness of ground state ferromagnetism in the presence of a long-range Coulomb interaction and long-range as well as short-range interdot hopping by modeling a wide range of different plaquette geometries accessible by arranging a few (～4) quantum dots in a controlled manner. We find that ferromagnetism is robust to the presence of long-range Coulomb interactions, and we develop conditions constraining the tunneling strength such that the ground state is ferromagnetic. Additionally, we predict the presence of a partially spin-polarized ferromagnetic state for 4 electrons in a Y-shaped 4-quantum-dot plaquette. Finally, we consider 4 electrons in a ring of 5 dots. This does not satisfy the Nagaoka condition; however, we show that the ground state is spin 1 for strong, but not infinite, on-site interaction. Thus, even though Nagaoka’s theorem does not apply, the ground state for the finite system with one hole in a ring of 5 dots is partially ferromagnetic. We provide detailed fully analytical results for the existence or not of ferromagnetic ground states in several quantum dot geometries which can be studied in currently available coupled quantum dot systems.
关键词： long-range Coulomb interactions,Nagaoka ferromagnetism,interdot tunneling,ferromagnetic ground states,quantum dot plaquettes
更新于2025-09-12 10:27:22
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Transparent Collision Visualization of Point Clouds Acquired by Laser Scanning
摘要： Exploring two-dimensional (2D) materials with room-temperature ferromagnetism and large perpendicular magnetic anisotropy is highly desirable but challenging. Here, through first-principles calculations, we propose a viable strategy to achieve such materials based on transition metal (TM) embedded borophene nanosheets. Due to electron deficiency, the commonly existent hexagon boron vacancies in various borophene phases serve as intrinsic anchor points for electron-rich transition metals, which not only adsorb strongly upon the vacancies but also favor to be embedded into the vacancies, forming 2D planar hybrid nanosheets. The adsorption-to-embedding transition is feasible thermodynamically and kinetically, owing to its exothermic nature and relatively small kinetic barriers. After embedding, phase transition is further proposed to obtain diverse structures of TM embedded borophenes with versatile magnetic properties. Based on the example of χ3 phase borophene, several ferromagnetic TM embedded borophene nanosheets with high Curie temperature and large perpendicular magnetic anisotropy have been predicted.
关键词： transition metal embedded borophene nanosheets,first-principles calculations,perpendicular magnetic anisotropy,room-temperature ferromagnetism,two-dimensional materials
更新于2025-09-11 14:15:04