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Theoretical study on the improvement of the doping efficiency of Al in 4H-SiC by co-doping group-IVB elements 下载免费PDF全文
Yuanchao Huang 《中国物理 B》2022,31(4):46104-046104
The p-type doping efficiency of 4H silicon carbide (4H-SiC) is rather low due to the large ionization energies of p-type dopants. Such an issue impedes the exploration of the full advantage of 4H-SiC for semiconductor devices. In this study, we show that co-doping group-IVB elements effectively decreases the ionization energy of the most widely used p-type dopant, i.e., aluminum (Al), through the defect-level repulsion between the energy levels of group-IVB elements and that of Al in 4H-SiC. Among group-IVB elements Ti has the most prominent effectiveness. Ti decreases the ionization energy of Al by nearly 50%, leading to a value as low as ~0.13 eV. As a result, the ionization rate of Al with Ti co-doping is up to ~5 times larger than that without co-doping at room temperature when the doping concentration is up to 1018 cm-3. This work may encourage the experimental co-doping of group-IVB elements such as Ti and Al to significantly improve the p-type doping efficiency of 4H-SiC. 相似文献
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Eva Lucaccini Matteo Briganti Dr. Mauro Perfetti Dr. Laure Vendier Dr. Jean‐Pierre Costes Dr. Federico Totti Prof. Dr. Roberta Sessoli Prof. Dr. Lorenzo Sorace 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5552-5562
The magnetic behaviour of a Dy(LH)3 complex (LH? is the anion of 2‐hydroxy‐N′‐[(E)‐(2‐hydroxy‐3‐methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising‐type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non‐equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising‐type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure DyIII phase and YIII diluted phase, which showed two different relaxation channels in zero and non‐zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet. 相似文献
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Weak Ligand‐Field Effect from Ancillary Ligands on Enhancing Single‐Ion Magnet Performance 下载免费PDF全文
Yin‐Shan Meng Prof. Dr. Yi‐Quan Zhang Prof. Dr. Zhe‐Ming Wang Prof. Dr. Bing‐Wu Wang Prof. Dr. Song Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12724-12731
A series of bis‐pentamethylcyclopentadienyl‐supported Dy complexes containing different ancillary ligands were synthesized and characterized. Magnetic studies showed that 1 Dy [Cp*2DyCl(THF)], 1 Dy’ [Cp*2DyCl2K(THF)]n, 2 Dy [Cp*2DyBr(THF)], 3 Dy [Cp*2DyI(THF)] and 4 Dy [Cp*2DyTp] (Tp=hydrotris(1‐pyrazolyl)borate) were single‐ion magnets (SIMs). The 1D dysprosium chain 1 Dy’ exhibited a hysteresis at up to 5 K. Furthermore, 3 Dy featured the highest energy barrier (419 cm?1) among the complexes. The effects of ancillary ligands on single‐ion magnetic properties were studied by experimental, ab initio calculations and electrostatic analysis methods in detail. These results demonstrated that the QTM rate was strongly dependent on the ancillary ligands and that a weak equatorial ligand field could be beneficial for constructing Dy‐SIMs. 相似文献
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Simultaneous Aromatic–Beryllium Bonds and Aromatic–Anion Interactions: Naphthalene and Pyrene as Models of Fullerenes,Carbon Single‐Walled Nanotubes,and Graphene 下载免费PDF全文
Dr. Marta Marín‐Luna Prof. Ibon Alkorta Prof. José Elguero Prof. Otilia Mó Prof. Manuel Yáñez 《Chemphyschem》2015,16(12):2680-2686
The possibility of forming stable BeR2:ArH:Y? (R=H, F, Cl; ArH=naphthalene, pyrene; Y=Cl, Br) ternary complexes in which the beryllium compounds and anions are located on the opposite sides of an extended aromatic system is explored by means of MP2/aug‐cc‐pVDZ ab initio calculations. Comparison of the electron‐density distribution of these ternary complexes with the corresponding BeR2:ArH and ArH:Y? binary complexes reveals the existence of significant cooperativity between the two noncovalent interactions in the triads. The energetic effects of this cooperativity are quantified by evaluation of the three‐body interaction energy Δ3E in the framework of the many‐body interaction‐energy (MBIE) approach. Although an essential component of the interaction energies is electrostatic and is well reflected in the changes in the molecular electrostatic potential of the aromatic system on complexation, strong polarization effects, in particular for the BeR2:ArH interactions, also play a significant role. The charge transfers associated with these polarization effects are responsible for significant distortion of both the BeR2 and the aromatic moieties. The former are systematically bent in all the complexes, and the latter are curved to a degree that depends on the nature of the R substituents of the BeR2 subunit. 相似文献
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Dmitry Sharapa Prof. Andreas Hirsch Prof. Bernd Meyer Prof. Timothy Clark 《Chemphyschem》2015,16(10):2165-2171
Ab initio and DFT calculations are used to investigate the structure, electronic properties, spectra and reactivity of cubic C8, which is predicted to be aromatic according to Hirsch′s rule. Although highly strained and with a small amount of diradical character, the carbon cube represents a surprisingly deep minimum and should therefore be observable as an isolated molecule. It is, however, predicted to be very reactive, both with itself and triplet oxygen. Calculated IR, Raman, and UV/Vis spectra are provided to aid identification of cubic C8 should it be synthesized. 相似文献
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Janine George Christoph Reimann Dr. Volker L. Deringer Prof. Dr. Thomas Bredow Prof. Dr. Richard Dronskowski 《Chemphyschem》2015,16(4):728-732
We report on an erroneous ground state within common density functional theory (DFT) methods for the solid elements bromine and iodine. Phonon computations at the GGA level for both molecular crystals yield imaginary vibrational modes, erroneously indicating dynamic instability—that fact alone could easily pass as a computational artefact, but these imaginary modes lead to energetically more favorable and dynamically stable structures, made up of infinite monoatomic chains. In contrast, meta‐GGA and hybrid functionals yield the correct energetic order for bromine, while for iodine, most global hybrids do not improve the GGA result significantly. The qualitatively correct answer, in both cases, is given by the long‐range corrected hybrid LC‐ωPBE, the Minnesota functionals M06L and M06, and by periodic Hartree–Fock and MP2 theory. This poor performance of economic DFT functionals should be kept in mind, for example, during global structure optimizations of systems with significant contributions from halogen bonds. 相似文献
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