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The effect of antisite defects and their density on monolayer hexagonal boron nitride is discussed in detail. Different supercell sizes to simulate different defect densities are set up. All structures containing antisites are fully optimized. It is indicated that the high density of antisite defects leads to the instability of the BB bond. The influence of supercell size on lattice structure is also summarized. Like vacancies and dopant atoms, the antisite defects also lead to the appearance of the defect energy band. Different antisite defect densities have different effects on different orbitals. Electron energy‐loss spectroscopy theoretical simulation is conducted on a single atom to analyze the influence of antisite defect density on the electronic structure of a single atom. It is shown that the high density of antisite defects makes the σ* transition of B atoms that are far away from the defect more preferred than π* transition, while it has less influence on the transition of central N atoms of the antisite defect NB because of the influence of neighboring atoms. The concentration of antisite defects plays a key role in manipulating the physical properties of monolayer hexagonal boron nitride and is helpful in expanding potential application scenarios. [ABSTRACT FROM AUTHOR]

We synthesized Nb x Mo 1-x O 2 series compounds and determined the structure of each component through x-ray diffraction and selected area electron diffraction techniques. For x=0.05, 0.1, 0.2, they possess room temperature MoO 2 monoclinic structure (P 2 1 / c); for x=0.25, 0.3, they become to body-centered tetragonal structure (I 4 1 / a); for x=0.33, 0.6, 0.65, they further turn to TiO 2 rutile-type structure (P 4 2 / mnm). Nb 0.25 Mo 0.75 O 2 has transport and magnetic properties similar to those of NbMoO 4 as paramagnetic metal. Moreover, the UV–vis spectra indicate the metallic property of Nb 0.05 Mo 0.95 O 2 , Nb 0.25 Mo 0.75 O 2 , and Nb 0.6 Mo 0.4 O 2. X-ray absorption spectra at the Mo-L 3 and Nb-L 3 edges present Mo4+/Nb4+ and Mo4+/Nb5+ valence state for Nb 0.25 Mo 0.75 O 2 and Nb 0.05 Mo 0.95 O 2 , respectively. This means the latter can be descripted as Nb 0.05 Mo 0.95 O 2+δ with δ = 0.025. We synthesized a series of compounds Nb x Mo 1-x O 2 and identified the different structures corresponding to various components through XRD analyses and SAED experiments. Furthermore, we conducted physical property studies on the compounds with different compositions. [Display omitted] • Successfully synthesized Nb x Mo 1-x O 2 , including unreported components. • Nb x Mo 1-x O 2 has diverse structures with different chemical contents. • Determining the transport properties of Nb x Mo 1-x O 2. [ABSTRACT FROM AUTHOR]

Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure‐induced disordering could require recognition of an order–disorder transition in solid‐state physics/chemistry and geophysics. Double perovskites Y2CoIrO6 and Y2CoRuO6 polymorphs synthesized at 0, 6, and 15 GPa show B‐site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long‐range ferrimagnetic ordering in the B‐site ordered samples are gradually overwhelmed by B‐site disorder. Theoretical calculations suggest that unusual unit‐cell compressions under external pressures unexpectedly stabilize the disordered phases of Y2CoIrO6 and Y2CoRuO6. [ABSTRACT FROM AUTHOR]

Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure‐induced disordering could require recognition of an order–disorder transition in solid‐state physics/chemistry and geophysics. Double perovskites Y2CoIrO6 and Y2CoRuO6 polymorphs synthesized at 0, 6, and 15 GPa show B‐site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long‐range ferrimagnetic ordering in the B‐site ordered samples are gradually overwhelmed by B‐site disorder. Theoretical calculations suggest that unusual unit‐cell compressions under external pressures unexpectedly stabilize the disordered phases of Y2CoIrO6 and Y2CoRuO6. [ABSTRACT FROM AUTHOR]

Integration of oxides with Si opens promising opportunities for novel multifunctional devices and new applications. To optimize the device performances through the hybrid integration, keeping the oxide/Si interface abrupt is critically important and challenging due to the seemingly unavoidable formation of amorphous SiO x or silicide interfacial layers. Here, we report an interface-engineering approach to this issue by molecular beam epitaxy. A BeO thin layer (∼5 nm) was deposited on Si (111) surface using a two-step process of Be deposition and oxidation. The initially formed BeO served as a template for subsequent homo-epitaxial growth of a 10-nm crystalline BeO layer. The well-defined interface between BeO and Si is clearly discerned by high-resolution transmission electron microscopy, implying the role of crystalline BeO as a barrier layer against oxygen atoms' diffusion. High-resolution X-ray photoelectron spectroscopy further confirmed that the combined BeO layers sufficiently protect the Si surface from oxidation. A bottom-gate enhancement-mode thin film transistor was established on a ZnO (130 nm)/BeO (70 nm)/Si architecture, where BeO was functionalized both as a diffusion barrier and as a high- k gate insulator. It indicates that this methodology can be potentially extended to hybrid integration of other technologically important crystalline oxides with Si infrastructures. [ABSTRACT FROM AUTHOR]

ZnS nanotetrapods synthesized via a solvothermal route have a octahedral core with a zincblende (ZB) structure and four hexprism-shaped arms consisting of alternately stacking ZB and wurtzite (WZ) phases, where the WZ phase has a higher volume percentage.In situangular-dispersive X-ray diffraction (ADXRD) measurements were carried out to study the structural behavior of ZnS nanotetrapods under high pressure up to 41.3 GPa. The initial WZ structure exhibits a very high mechanical stability to ∼11.3 GPa. Both the WZ and ZB structures transform to the rocksalt (RS) structure at ∼15.4 GPa. The bulk moduli of the WZ (148.2 ± 8.9 GPa) and RS (165.6 ± 9.9 GPa) phases are both larger than the previously reported values. These phenomena are discussed based on the alternating epitaxial growth of the WZ and ZB phases in the arms of nanotetrapods. Our study suggests that the internal structure of nanomaterials could also greatly affect their stability and transition behavior. [ABSTRACT FROM PUBLISHER]