arXiv subjects

Mingsu Si

Publications and source records attributed to Mingsu Si.

5 recordsLinked to original sources

arXiv2026

Origin of anomalous p-type conductivity in monolayer Fe-doped MoS2

Substitutional doping effectively modulates carrier polarity of semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) like MoS2. Although Fe doping typically induces n-type conductivity in monolayer MoS2, anomalous p-type behavior has also been experimentally reported, the origin of which remains unresolved. Here, we prove that this anomalous p-type conductivity originates from defect associates formed through interactions between Fe dopants and S atoms, which consists of three Fe substituting Mo (FeMo) point defects arranged into an equilateral triangle with a central S atom, denoted as 3FeMo-S associate. Its p-type effect is directly verified through scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS) measurement, in sharp contrast to the n-type behavior induced by isolated FeMo point defects, and the conclusion is further supported by electrical transport measurements and first-principles calculations. Similar 3FeW-S associates and their p-type doping effect are also identified in monolayer Fe-doped WS2. This work resolves a longstanding controversy and highlights the critical role of defect associates in modulating properties of 2D TMDs.

cond-mat.mtrl-sci↗

arXiv2024

Tunable high Chern-number quantum anomalous Hall effect through interlayer ferromagnetic coupling in two-dimensional ferromagnet NiSbO3

The high Chern-number quantum anomalous Hall effect (QAHE) is significant and fascinating due to the presence of multiple dissipationless chiral edge states. Here, we predict that monolayer NiSbO3 possesses the Chern number C = 3, confirmed by the anomalous Hall conductance and the chiral edge states. The magnetic anisotropic energy (MAE) responsible for ferromagnetic order is 0.641 meV originating from Ni-d and Sb-p orbitals, where the contributed MAE from same spin-up channels predominates. In forward electric fields, the negative MAE makes the easy magnetization direction perpendicular to the surface, which is conducive to the realizing of high Chern-number QAHE. The simulated Curie temperature is 291 K. Intriguingly, in a bilayer, the obtained C = 6 is twice that of the monolayer, thanking to the interlayer ferromagnetic coupling. Our work offers a promising candidate for potential applications in topological quantum devices and spintronics.

cond-mat.mes-hall↗

arXiv2016

Band gap modulation in γ-graphyne by p-n codoping

The modulation of band gap in the two-dimensional carbon materials is of impor- tance for their applications as electronic devices. By first-principles calculations, we propose a model to control the band gap size of γ-graphyne. The model is named as p-n codoping, i. e., using B and N atoms to codope into γ-graphyne. After codoping, B atom plays a role of p doping and N atom acts as n doping. The Fermi energy level returns around the forbidden zone and the band gap of γ-graphyne vary bigger or smaller. Moreover, the gaps exhibit an oscillated behaviour in different codoping configurations. The proposed model serves as new insights for better modulation of the electronic properties of 2D carbon materials.

cond-mat.mes-hall↗

arXiv2016

The mechanism and process of spontaneous boron doping in graphene in the theoretical perspective

A theoretical model is presented to reveal the mechanism of B doping into graphene in the microwave plasma experiment choosing trimethylboron as the doping source (ACS NANO 6 (2012) 1970). The results show that the reason for B doping comes from the combinational interaction of B and other groups (C, H, CH, CH2 or CH3) decomposing from trimethylboron and the doping undergoes two crucial steps. The minimal energy path for the first step are determined. The obtained energy barrier of considered cases fall into the range of 0.02-0.43 eV, supporting the fact that the substituting B for C can easily realized even at room temperature. As the second step, after removing irrelevant groups in vertical direction through H saturation, the perfect B doping is realized at last. This work successfully explain the above experimental phenomenon and propose a novel and feasible method aiming at B doping of graphene.

cond-mat.mes-hall↗

arXiv2012

g-B3N3C: a novel two-dimensional graphite-like material

A novel crystalline structure of hybrid monolayer hexagonal boron nitride (BN) and graphene is predicted by means of the first-principles calculations. This material can be derived via boron or nitrogen atoms substituted by carbon atoms evenly in the graphitic BN with vacancies. The corresponding structure is constructed from a BN hexagonal ring linking an additional carbon atom. The unit cell is composed of 7 atoms, 3 of which are boron atoms, 3 are nitrogen atoms, and one is carbon atom. It behaves a similar space structure as graphene, which is thus coined as g-B3N3C. Two stable topological types associated with the carbon bonds formation, i.e., C-N or C-B bonds, are identified. Interestingly, distinct ground states of each type, depending on C-N or C-B bonds, and electronic band gap as well as magnetic properties within this material have been studied systematically. Our work demonstrates practical and efficient access to electronic properties of two-dimensional nanostructures providing an approach to tackling open fundamental questions in bandgap-engineered devices and spintronics.

cond-mat.mes-hall↗