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Despite exhibiting their attractive properties and performances, the interlayer interaction in two-dimensional van der Waals epitaxy heterostructures is not well understood. Here, we demonstrate the growth of two dimensional vertically stacked multilayer β-In2Se3/monolayer WS2 heterostructures via the chemical vapor deposition method. Despite a large lattice misfit (29.9%), the vertically stacked β-In2Se3/WS2 heterostructures exhibit van der Waals epitaxy with well-aligned lattice orientation of WS2(100)[001]//In2Se3(100)[001], forming a periodic superlattice. Interestingly, a reversible phase transformation of epitaxial β-In2Se3 has been observed by temperature-dependent Raman spectroscopy and electron diffraction conducted from liquid N2 to room temperature. Notably, the phase transformation of epitaxial β-In2Se3 can only be observed when its layer number is larger than 4 and the transformation temperature increases with the increase in the layer number, indicating a layer number dependent phase transformation of epitaxial β-In2Se3. These results indicate that the confinement effect exists between monolayer WS2 and epitaxial β-In2Se3, strongly constraining the lattice change of adjacent few layers of β-In2Se3.

Wafer-scale monolayer WS2 has been widely investigated. Here, we report a repeatable and low-cost one-step chemical vapor deposition method for the direct growth of a 4-in. monolayer WS2 film on a thermal oxide silicon wafer by using WO3 and H2S gas as precursors. H2S gas exhibits a high vulcanization ability and can effectively reduce the growth temperature of WS2 to 825 °C. The growth process follows a self-limiting growth to form a monolayer polycrystalline film, which is merged via many stable small-angle grain boundaries. The wafer-scale monolayer WS2 film shows uniform and high-quality electrical properties. This method helps promote the future production and application of wafer-scale monolayer sulfide.

Recently, intrinsic ferromagnetism of layered van der Waals compounds (such as CrCl3, CrI3, and Cr2Ge2Te6) has received widespread attention. Herein, layered van der Waals heterostructure composites of two dimensional layered magnetic material CrCl3 and graphene nanosheets (GNSs) are facilely obtained and investigated as microwave absorption materials. The complex permittivity and complex permeability of heterostructure composites can be adjusted by modulating the mass ratio of GNS and CrCl3. The real part and imaginary part of permittivity increase with the increase in the mass fraction of GNS in composites, due to the high conductivity of GNS. Thus, dielectric loss is enhanced and originates from the Debye relaxation process and the interfacial polarization process. The minimum reflection loss (RL) of the CrCl3-GNS heterostructure composite with a GNS mass fraction of 40 wt. % can reach −46.2 dB at a microwave frequency of 10 GHz with a thickness of 1.9 mm. In addition, the RL less than −10 dB can be achieved at different frequencies with all thicknesses (1–5 mm). This work might provide the practical application of two dimensional layered magnetic materials as ultrahigh-performance microwave absorption materials.

High efficiency, lightweight, and tunable microwave absorbing materials have drawn tremendous attention. Here, we have synthesized layered GeP5 bulk at high temperature and high pressure. Then, the GeP5 nanosheets are obtained by an efficient liquid-phase exfoliation method and display excellent microwave absorption performance as a microwave absorber. The reflection loss (RL) can achieve below −10 dB in a wide range of thicknesses and microwave frequencies. For further meeting the lightweight demand of microwave absorption materials, porous germanium (GeP5-570) is obtained from GeP5 via the annealing treatment. Microwave absorption characteristics can be significantly improved after annealing treatment. The minimum RL values of porous germanium (GeP5-570) can reach −37.8 dB at a microwave frequency of 4.7 GHz under a thickness of 2.9 mm. The effective absorption bandwidth (RL< −10 dB) of GeP5-570 is 11.8–14.3 GHz with a thickness of 1.2 mm. In addition, the RL value can attain −20 dB in the frequency range of 3.8–16.1 GHz with various thicknesses from 1.0 to 3.5 mm.

Pt fibers (15 μm) were coated with topological insulator Bi2Se3 nanoplates via a single mode microwave-assisted synthesis technique. With the Bi2Se3/Pt fibers, flexible memory devices were facilely assembled, and they were demonstrated to exhibit rewritable nonvolatile resistive switching characteristics of low switching voltage (−1.2 V and +0.7 V), high ON/OFF current ratio (106), and good retention (4500 s), showing the potential application in data storage. The resistive switching mechanism was analyzed on the bases of formation and rupture of conductive filaments.

The double resonance behavior of microwave magnetic permeability has been observed for multiwalled carbon nanotube composites containing Ni catalyst. One of them is due to the natural resonance at 6.00GHz and another is due to the exchange resonance at 10.11GHz. The natural resonance is dependent on magnetocrystalline anisotropy and shape anisotropy of Ni nanostick catalyst and the calculated result of exchange resonance mode with a few modifications was close to the experiment. It is believed that the coexistence of natural resonance and exchange resonance is benefial to large bandwidth as a microwave absorber.