arXiv subjects

Huixia Fu

Publications and source records attributed to Huixia Fu.

22 records · Page 2Linked to original sources

arXiv2018

Self-Modulation Doping Effect in the High-Mobility Layered Semiconductor Bi2O2Se

Recently an air-stable layered semiconductor Bi2O2Se was discovered to exhibit an ultrahigh mobility in transistors fabricated with its thin layers. In this work, we explored the mechanism that induces the high mobility and distinguishes Bi2O2Se from other semiconductors. We found that the electron donor states lie above the lowest conduction band. Thus, electrons get spontaneously ionized from donor sites (e.g., Se vacancies) without involving the thermal activation, different from the donor ionization in conventional semiconductors. Consequently, the resistance decreases as reducing the temperature as observed in our measurement, which is similar to a metal but contrasts to a usual semiconductor. Furthermore, the electron conduction channels locate spatially away from ionized donor defects (Se vacancies) in different van der Waals layers. Such a spatial separation can strongly suppress the scattering caused by donor sites and subsequently increase the electron mobility, especially at the low temperature. We call this high-mobility mechanism self-modulation doping, i.e. the modulation doping spontaneously happening in a single-phase material without requiring a heterojunction. Our work paves a way to design novel high-mobility semiconductors with layered materials.

cond-mat.mes-hall↗

arXiv2017

Large Magnetic Anisotropy of an Iron-Porphyrin Complex on Metal Substrate

Single magnetic atoms or molecules with large single-ion magnetic anisotropy are highly desired for future applications in high-density data storage and quantum computation. Here we have synthesized an Fe-porphyrin complex on Au(111) substrate in a controlled way, and revealed large magnetic anisotropy energy of more than 15 meV by low-temperature scanning tunneling microscopy and spectroscopy. Two magnetic states with opposite spin directions are discriminated by inelastic electron tunneling spectroscopy in varied magnetic field, and are found to have long spin lifetimes. First-principle calculations reveal that the weak ligand filed in this complex keeps the Fe atom in a high-spin state and preserves its large orbital angular momentum, which gives rise to an easy-axis perpendicular to the molecular plane and large magnetic anisotropy energy by spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2016

Magnetic Dirac Fermions and Chern Insulator Supported on Pristine Silicon Surface

Emergence of ferromagnetism in non-magnetic semiconductors is strongly desirable, especially in topological materials thanks to the possibility to achieve quantum anomalous Hall effect. Based on first-principles calculations, we propose that for Si thin film grown on metal substrate, the pristine Si(111)-root3xroot3 surface with a spontaneous weak reconstruction has a strong tendency of ferromagnetism and nontrivial topological properties, characterized by spin polarized Dirac-fermion surface states. In contrast to conventional routes relying on introduction of alien charge carriers or specially patterned substrates, the spontaneous magnetic order and spin-orbit coupling on the pristine silicon surface together gives rise to quantized anomalous Hall effect with a finite Chern number C=-1. This work suggests exciting opportunities in silicon-based spintronics and quantum computing free from alien dopants or proximity effects.

cond-mat.mes-hall↗

arXiv2015

From Silicene to Half-Silicane by Hydrogenation

Graphane is graphene fully hydrogenated from both sides, forming a 1x1 structure, where all C atoms are in sp3 configuration. In silicene, the Si atoms are in a mix-sp2/sp3 configuration, it is therefore natural to imagine silicane in analogue to graphane. However, monoatomic silicene sheet grown on substrates generally reconstructs into different phases, and only partially hydrogenated silicene with reconstructions had been reported before. In this report we produce half-silicane, where one Si sublattice is fully H-saturated and the other sublattice is intact, forming a perfect 1x1 structure. By hydrogenating various silicene phases on Ag(111) substrate, we found that only the (2r3x2r3)R30° phase can produce half-silicane. Interestingly, this phase was previous considered to be a highly defective or incomplete silicene structure. Our results indicate that the structure of (2r3x2r3)R30° phase involves a complete silicene-1x1 lattice instead of defective fragments, and the formation mechanism of half-silicane was discussed with the help of first principles calculations.

cond-mat.mtrl-sci↗