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[ASAP] Ultrafast Electron Cooling and Decay in Monolayer WS2 Revealed by Time- and Energy-Resolved Photoemission Electron Microscopy
[ASAP] Ultraheavy and Ultrarelativistic Dirac Quasiparticles in Sandwiched Graphenes
[ASAP] Direct Measurement of the Contents, Thickness, and Internal Pressure of Molybdenum Disulfide Nanoblisters
[ASAP] Non-Invasive Nanoscale Potentiometry and Ballistic Transport in Epigraphene Nanoribbons
[ASAP] Planar Hypercoordinate Motifs in Two-Dimensional Materials
CVD growth of large-area InS atomic layers and device applications
DOI: 10.1039/D0NR01104E, Communication
Indium sulfide (InS) atomic layers made by chemical vapor deposition (CVD) are synthesized onto a mica substrate, producing a highly crystalline, large-area, and atomically thin-film InS flakes.
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Direct observation of minibands in a twisted graphene/WS2 bilayer
Stacking two-dimensional (2D) van der Waals materials with different interlayer atomic registry in a heterobilayer causes the formation of a long-range periodic superlattice that may bestow the heterostructure with properties such as new quantum fractal states or superconductivity. Recent optical measurements of transition metal dichalcogenide (TMD) heterobilayers have revealed the presence of hybridized interlayer electron-hole pair excitations at energies defined by the superlattice potential. The corresponding quasiparticle band structures, so-called minibands, have remained elusive, and no such features have been reported for heterobilayers composed of a TMD and another type of 2D material. We introduce a new x-ray capillary technology for performing microfocused angle-resolved photoemission spectroscopy with a spatial resolution of ~1 μm, and directly observe minibands at certain twist angles in mini Brillouin zones (mBZs). We discuss their origin in terms of initial and final state effects by analyzing their dispersion in distinct mBZs.
Picoscale structural insight into superconductivity of monolayer FeSe/SrTiO3
Remarkable enhancement of the superconducting transition temperature (Tc) has been observed for monolayer (ML) FeSe films grown on SrTiO3 substrates. The atomic-scale structure of the FeSe/SrTiO3 interface is an important determinant of both the magnetic and interfacial electron-phonon interactions and is a key ingredient to understanding its high-Tc superconductivity. We resolve the atomic-scale structure of the FeSe/SrTiO3 interface through a complementary analysis of scanning transmission electron microscopy and in situ surface x-ray diffraction. We find that the interface is more strongly bonded for a particular registration, which leads to a coherently strained ML. We also determine structural parameters, such as the distance between ML FeSe and the oxide, SeFeSe bond angles, layer-resolved distances between FeSe, and registry of the FeSe lattice relative to the oxide. This picoscale structure determination provides an explicit structural framework and constraint for theoretical approaches addressing the high-Tc mechanism in FeSe/SrTiO3.
Black phosphorus quantum dots in inorganic perovskite thin films for efficient photovoltaic application
Black phosphorus quantum dots (BPQDs) are proposed as effective seed-like sites to modulate the nucleation and growth of CsPbI2Br perovskite crystalline thin layers, allowing an enhanced crystallization and remarkable morphological improvement. We reveal that the lone-pair electrons of BPQDs can induce strong binding between molecules of the CsPbI2Br precursor solution and phosphorus atoms stemming from the concomitant reduction in coulombic repulsion. The four-phase transition during the annealing process yields an α-phase CsPbI2Br stabilized by BPQDs. The BPQDS/CsPbI2Br core-shell structure concomitantly reinforces a stable CsPbI2Br crystallite and suppresses the oxidation of BPQDs. Consequently, a power conversion efficiency of 15.47% can be achieved for 0.7 wt % BPQDs embedded in CsPbI2Br film-based devices, with an enhanced cell stability, under ambient conditions. Our finding is a decisive step in the exploration of crystallization and phase stability that can lead to the realization of efficient and stable inorganic perovskite solar cells.
A sensitive and robust thin-film x-ray detector using 2D layered perovskite diodes
Solid-state radiation detectors, using crystalline semiconductors to convert radiation photons to electrical charges, outperform other technologies with high detectivity and sensitivity. Here, we demonstrate a thin-film x-ray detector comprised with highly crystalline two-dimensional Ruddlesden-Popper phase layered perovskites fabricated in a fully depleted p-i-n architecture. It shows high diode resistivity of 1012 ohm·cm in reverse-bias regime leading to a high x-ray detecting sensitivity up to 0.276 C Gyair–1 cm–3. Such high signal is collected by the built-in potential underpinning operation of primary photocurrent device with robust operation. The detectors generate substantial x-ray photon–induced open-circuit voltages that offer an alternative detecting mechanism. Our findings suggest a new generation of x-ray detectors based on low-cost layered perovskite thin films for future x-ray imaging technologies.
Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer
Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO3 monolayers by inducing a spin reorientation in (SrRuO3)1/(SrTiO3)N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial <001> direction (N < 3) to eightfold <111> directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO3 monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO3. First-principle calculations reveal that increasing the SrTiO3 layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO3 monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications.