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.     

Interlayer coupling effect in van der Waals heterostructures of transition metal dichalcogenides

Van der Waals(vdW)heterobilayers formed by two-dimensional(2D)transition metal dichalcogenides(TMDCs)created a promising platform for various electronic and optical properties,ab initio band results indicate that the band offset of type-Ⅱband alignment in TMDCs vdW heterobilayer could be tuned by introducing Janus WSSe monolayer,instead of an external electric field.On the basis of symmetry analysis,the allowed interlayer hopping channels of TMDCs vdW heterobilayer were determined,and a four-level k·p model was developed to obtain the interlayer hopping.Results indicate that the interlayer coupling strength could be tuned by interlayer electric polarization featured by various band offsets.Moreover,the difference in the formation mechanism of interlayer valley excitons in different TMDCs vdW heterobilayers with various interlayer hopping strength was also clarified.     

Realization of single and double axial InSb–GaSb heterostructure nanowires

Heteroepitaxial growth of III‐Sb nanowires allows for the formation of various interesting complex structures and enables the combination of their remarkable properties. In this Letter, we investigate the heteroepitaxial growth of Au‐seeded InSb and GaSb nanowires using metalorganic vapor phase epitaxy. We demonstrate successful single and double axial InSb–GaSb heterostructures in both directions. The formation properties of the grown nanowires including the compositional change of the particle and the interface sharpness are further discussed. In addition, the decomposition of InSb and GaSb segments and their side facet evolution are explained.

     

Silicon carbide nanocrystals growth on Si(1 0 0) and Si(1 1 1) from a chemisorbed methanol layer

SiC nanocrystals are grown at high temperature on Si(1 0 0) and Si(1 1 1) surfaces starting from a chemisorbed layer of methanol. The decomposition of this layer allows to have a well defined amount of carbon to feed SiC growth. Nanocrystals ranging from 10 nm to 50 nm with density from 100 μm⁻² to 1500 μm⁻² are obtained, and the total volume of produced SiC corresponds to carbon provided by the chemisorbed organic layer. Large differences in nanocrystal size and density, as well as in surface roughness, are observed depending on substrate orientation. The internal structure, crystallinity and epitaxy of nanocrystals grown on Si(1 0 0) are studied using cross-sectional transmission electron microscopy (XTEM), methanol adsorption and surface evolution using scanning tunnelling microscopy (STM). The joint application of XTEM and STM techniques allows a complete characterization of the geometry and chemical composition of these nanostructures.     

Effect on alloying at the Fe/Ni(001) interfaces on the interlayer exchange coupling

We investigate the stability of various ordered FeNi alloys at the interfaces of Fe/Ni superlattices by using ab initio density functional calculation. We consider an Fe_0.5Ni_0.5 ordered alloy of one or two monolayers thick at different positions beyond the interface and the possibility of an interdiffusion of a complete monolayer of Ni(Fe) in Fe(Ni) slab. An interfacial atomic layer of Fe_0.5Ni_0.5 exchanged with its adjacent Ni monolayers, leading to a buffer zone of Ni₃Fe composition is found to be the most stable structural configuration. For this atomic arrangement we investigate the magnetic profile and the resulting interlayer exchange coupling between the Ni slabs for Fe spacer thickness of 0 to 4 monolayers.     

Epitaxial ferromagnetic thin films and heterostructures of Mn-based metallic and semiconducting compounds on GaAs

We present two approaches to integrate magnetic materials with III–V semiconductors. One is epitaxial ferromagnetic metallic films and heterostructures on GaAs (0 0 1) substrates. Although crystal structure, lattice constant, chemical bonding and other properties are dissimilar, ferromagnetic hexagonal MnAs thin films and MnAs/NiAs ferromagnet/nonmagnet heterostructures (HSs) are grown on GaAs by molecular beam epitaxy (MBE). Multi-stepped magnetic hysteresis are controllably realized in MnAs/NiAs HSs, making this material promising for the application to multi-level nonvolatile recording on semiconductors. The other approach is to prepare a new class of GaAs based magnetic semiconductor, GaMnAs, by low-temperature molecular beam epitaxy (LT-MBE) on GaAs (0 0 1). New III–V based superlattices consisting of ferromagnetic semiconductor GaMnAs and nonmagnetic semiconductor AlAs are also successfully grown. Structural and magnetic properties of these new heterostructures are presented.     

Transition metal dichalcogenides (TMDCs) heterostructures: Optoelectric properties

Transition metal dichalcogenides (TMDCs) have suitable and adjustable band gaps, high carrier mobility and yield. Layered TMDCs have attracted great attention due to the structure diversity, stable existence in normal temperature environment and the band gap corresponding to wavelength between infrared and visible region. The ultra-thin, flat, almost defect-free surface, excellent mechanical flexibility and chemical stability provide convenient conditions for the construction of different types of TMDCs heterojunctions. The optoelectric properties of heterojunctions based on TMDCs materials are summarized in this review. Special electronic band structures of TMDCs heterojunctions lead to excellent optoelectric properties. The emitter, p-n diodes, photodetectors and photosensitive devices based on TMDCs heterojunction materials show excellent performance. These devices provide a prototype for the design and development of future high-performance optoelectric devices.     

Cobalt Growth on the Tips of CdSe Nanorods

Best of both worlds : Reduction of an organometallic Co precursor on preformed CdSe nanorods yields two distinct semiconducting–magnetic heterostructures (see picture). The selective growth of Co on the tips of CdSe first gives nanosphere–nanorod dimers, which evolve into nanorod–nanorod structures. In the hybrid objects the magnetic properties of Co remain intact, while the luminescence properties of CdSe are affected but not completely quenched.

     

Magnetic shape anisotropy calculations of Fe nanostructures at the Si/Fe(1 1 1) interface

The influence of Si capping layers on the magnetic properties of thin Fe films grown on Si(1 1 1) has been studied by means of shape anisotropy calculations. Fe surface morphology simulations are realized using experimental STM data. Surface modifications induced by the interaction between the Si overlayer and the Fe surface are performed in agreement with the model proposed in a previous work by Stephan et al. [J. Magn. Mater. 293 (2005) 746]. Calculations of the uniaxial anisotropy energy constant K_u are then performed on the modified Fe surface morphology for different Si deposition geometries as proposed in the model. The relevant data deduced by this method such as anisotropy constants and their related easy axis direction, are directly compared to the experimental ones obtained by ex situ magneto-optical Kerr effect (MOKE) measurements at room temperature using the transverse bias initial inverse susceptibility and torque (TBIIST) method. We show that a very good agreement between those results leads to a confirmation of the proposed model.