二维磁性过渡金属卤化物的分子束外延制备及物性调控

二维磁性材料的自发磁化可以维持到单层极限下,为在二维尺度理解和调控磁相关性质提供了一个理想的平台,也使其在光电子学和自旋电子学等领域具有重要的应用前景.晶体结构为层状堆叠的过渡金属卤化物具有部分填充的d轨道和较弱的范德瓦耳斯层间相互作用等特性,是合适的二维磁性候选材料.结合分子束外延(MBE)技术,不仅可以精准调控二维磁性材料生长达到单层极限,而且可以结合扫描隧道显微术等先进实验技术开展原子尺度上的物性表征和调控.本文详细介绍了多种二维磁性过渡金属卤化物的晶体结构和磁结构,并展示了近几年来通过MBE技术生长的二维磁性过渡金属卤化物以及相应的电学和磁学性质.随后,讨论了基于MBE方法对二维磁性过渡金属卤化物的物性进行调控的方法,包括调控层间堆垛、缺陷工程以及构筑异质结.最后,总结并展望了二维磁性过渡金属卤化物研究领域在未来的发展机会与挑战.     

PHOTOLUMINESCENCE OF NANOCRYSTALLINE SiC FILMS PREPARED BY RF MAGNETRON SPUTTERING

Amorphous SiC films are deposited on Si (111) substrates by rf magnetron sputtering and then annealed at 1200℃ for different times by a dc self-heating method in a vacuum annealing system. The crystallization of the amorphous SiC is determined by Raman scattering at room temperature and X-ray diffraction. The experimental result indicates that the SiC nanocrystals have formed in the films. The topography of the as-annealed films is characterized by atomic force microscopy. Measurements of photoluminescence of the as-annealed films show blue or violet light emission from the nanocrystalline SiC films and photoluminescence peak shifts to short wavelength side as the annealing time decreases.     

Magnetic proximity effect induced spin splitting in two-dimensional antimonene/Fe3GeTe2 van der Waals heterostructures

Recently, two-dimensional van der Waals (vdW) magnetic heterostructures have attracted intensive attention since they can show remarkable properties due to the magnetic proximity effect. In this work, the spin-polarized electronic structures of antimonene/Fe₃GeTe₂ vdW heterostructures were investigated through the first-principles calculations. Owing to the magnetic proximity effect, the spin splitting appears at the conduction-band minimum (CBM) and the valence-band maximum (VBM) of the antimonene. A low-energy effective Hamiltonian was proposed to depict the spin splitting. It was found that the spin splitting can be modulated by means of applying an external electric field, changing interlayer distance or changing stacking configuration. The spin splitting energy at the CBM monotonously increases as the external electric field changes from -5 V/nm to 5 V/nm, while the spin splitting energy at the VBM almost remains the same. Meanwhile, as the interlayer distance increases, the spin splitting energies at the CBM and VBM both decrease. The different stacking configurations can also induce different spin splitting energies at the CBM and VBM. Our work demonstrates that the spin splitting of antimonene in this heterostructure is not singly dependent on the nearest Sb—Fe distance, which indicates that magnetic proximity effect in heterostructures may be modulated by multiple factors, such as hybridization of electronic states and the local electronic environment. The results enrich the fundamental understanding of the magnetic proximity effect in two-dimensional vdW heterostructures.