Using the first-principles density functional theory (DFT) calculations, we study the effects of Co adatom on the electronic and magnetic properties of monolayer WS<sub>2</sub>. The calculations show that,...Using the first-principles density functional theory (DFT) calculations, we study the effects of Co adatom on the electronic and magnetic properties of monolayer WS<sub>2</sub>. The calculations show that, for the high symmetry adsorption sites (Tw, H and Ts) on the surface of monolayer WS<sub>2</sub>, Co atom prefers Tw site. The p-d hybridization mechanism for the magnetism results in the splitting of the energy levels near the Fermi energy. A total magnetic moment of ~1.0 μB is found in WS<sub>2</sub> system with one Co adsorbed and local magnetic moment which mainly focuses on the adsorption site. For Tw adsorption position, we further investigate the formation energy of the ferromagnetic (FM) and the antiferromagnetic (AFM) states under different monolayer coverage (ML) of Co atoms. The FM configurations are relatively stable at 0.50 ML and 1.0 ML. The local density of states (LDOS) and band calculations reveal that both of them present half-metal ferromagnetic materials’ property, which are the important preparation materials for spintronic devices.展开更多
Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostruc...Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride （hBN） and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio （〉103） between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.展开更多
文摘Using the first-principles density functional theory (DFT) calculations, we study the effects of Co adatom on the electronic and magnetic properties of monolayer WS<sub>2</sub>. The calculations show that, for the high symmetry adsorption sites (Tw, H and Ts) on the surface of monolayer WS<sub>2</sub>, Co atom prefers Tw site. The p-d hybridization mechanism for the magnetism results in the splitting of the energy levels near the Fermi energy. A total magnetic moment of ~1.0 μB is found in WS<sub>2</sub> system with one Co adsorbed and local magnetic moment which mainly focuses on the adsorption site. For Tw adsorption position, we further investigate the formation energy of the ferromagnetic (FM) and the antiferromagnetic (AFM) states under different monolayer coverage (ML) of Co atoms. The FM configurations are relatively stable at 0.50 ML and 1.0 ML. The local density of states (LDOS) and band calculations reveal that both of them present half-metal ferromagnetic materials’ property, which are the important preparation materials for spintronic devices.
文摘Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride （hBN） and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio （〉103） between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.
