We demonstrate unidirectional enhanced photoluminescence from a monolayer MoS2 via Fano resonances in dielectric photonic crystals. The Fano resonances can also be dynamic controlled by optical and electrical tuning of the MoS2 refractive index.
The search of novel tools controlling the physical and chemical properties of matter at the nanoscale is crucial for developing next-generation integrated systems, with applications ranging from computing to medicine. Here, we show that thermal scanning probe lithography (t-SPL) can be a flexible tool for manipulating with nanoscale precision the surface properties of a wide range of specifically designed systems. In particular, we show that via t-SPL, we pattern nanoscale chemical patterns on polymeric substrates, which are then used to specifically bind extracellular matrix (ECM) proteins to the polymer surface. We demonstrate that the concentration of immobilized proteins can be controlled by varying the tip temperature, so that nanoscale protein gradients can be created. On a different system, we show that, by performing t-SPL on a thin film magnetic multilayer, in an external magnetic field, we are able to write reversibly magnetic patterns with arbitrarily oriented magnetization and tunable magnetic anisotropy. This demonstrates that t-SPL represents a novel, straightforward and extremely versatile method for the nanoscale engineering of the physicalchemical properties in a wide variety of materials.
Strong broadband absorption of unpolarized light in a large-area, thin film is important for photovoltaics, photodetectors, thermal emitters [1] and optical modulators. Graphene is a suitable material for absorbers, as its absorption bandwidth is very large, but a single layer of graphene absorbs only 2.3% [2].
Abstract Gate‐controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non‐layered materials. The non‐layered rhombohedral Cr 2 S 3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS 2 and 0D Cr 1/3 . Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined‐standing grown 2D Cr 2 S 3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all‐dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr 1/3 layers, as revealed by cross‐sectional scanning transmission electron microscope, permitting the insertion of Li + ions. An unprecedented metal‐insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr 2 S 3 ‐based ionic field‐effect transistors. Theoretical calculations corroborate the metallization induced by Li‐ion intercalation. This work sheds light on the understanding of growth mechanism, structure‐property correlation and highlights the diverse potential applications of 2D non‐layered Cr 2 S 3 superlattice.
The layered oxychalcogenide semiconductor Bi$_2$O$_2$Se (BOS) hosts a multitude of unusual properties including high electron mobility. Owing to similar crystal symmetry and lattice constants, the perovskite oxide SrTiO$_3$ (STO) has been demonstrated to be an excellent substrate for wafer-scale growth of atomically thin BOS films. However, the structural and electronic properties of the BOS/STO interface remain poorly understood. Here, through first-principles study, we reveal that polar discontinuities and interfacial contact configurations have a strong impact on the electronic properties of ideal BOS/STO interfaces. The lowest-energy [Bi-TiO$_2$] contact type, which features the contact between a Bi$_2$O$_2$ layer of BOS with the TiO$_2$-terminated surface of STO, incurs significant interfacial charge transfer from BOS to STO, producing a BOS/STO-mixed, $n$-type metallic state at the interface. By contrast, the [Se-SrO] contact type, which is the most stable contact configuration between BOS and SrO-terminated STO substrate, has a much smaller interfacial charge transfer from STO to BOS and exhibits $p$-type electronic structure with much weaker interfacial hybridization between BOS and STO. These results indicate that BOS grown on TiO$_2$-terminated STO substrates could be a fruitful system for exploring emergent phenomena at the interface between an oxychalcogenide and an oxide, whereas BOS grown on SrO-terminated substrates may be more advantageous for preserving the excellent intrinsic transport properties of BOS.
We report total absorption of unpolarized, wide bandwidth (800-1550 nm) light in 90 nm thick graphene-based metamaterial. Grooves in the metamaterial couple incoming light into the absorber's guided modes. Fabrication is low-cost and scalable.
Silicon (Si) photovoltaic devices present possible avenues for overcoming global energy and environmental challenges. The high reflection and surface recombination losses caused by the Si interface and its nanofabrication process are the main hurdles for pursuing a high energy conversion efficiency. However, recent advances have demonstrated great success in improving device performance via proper Si interface modification with the optical and electrical features of two-dimensional (2D) materials. Firmly integrating large-area 2D materials with 3D Si nanostructures with no gap in between, which is essential for optimizing device performance, has rarely been achieved by any technique due to the complex 3D morphology of the nanostructures. Here we propose the concept of a 3D conformal coating of graphene metamaterials, in which the 2D graphene layers perfectly adapt to the 3D Si curvatures, leading to a universal 20% optical reflection decrease and a 60% surface passivation improvement. In a further application of this metamaterial 3D conformal coating methodology to standard Si solar cells, an overall 23% enhancement of the solar energy conversion efficiency is achieved. The 3D conformal coating strategy could be readily extended to various optoelectronic and semiconductor device systems with peculiar performance, offering a pathway for highly efficient energy-harvesting and storage solutions.
Magnonics is gaining momentum as an emerging technology for information processing. The wave character and Joule heating-free propagation of spin-waves hold promises for highly efficient analog computing platforms, based on integrated magnonic circuits. Miniaturization is a key issue but, so far, only few examples of manipulation of spin-waves in nanostructures have been demonstrated, due to the difficulty of tailoring the nanoscopic magnetic properties with conventional fabrication techniques. In this Letter, we demonstrate an unprecedented degree of control in the manipulation of spin-waves at the nanoscale by using patterned reconfigurable spin-textures. By space and time-resolved scanning transmission X-ray microscopy imaging, we provide direct evidence for the channeling and steering of propagating spin-waves in arbitrarily shaped nanomagnonic waveguides based on patterned domain walls, with no need for external magnetic fields or currents. Furthermore, we demonstrate a prototypic nanomagnonic circuit based on two converging waveguides, allowing for the tunable spatial superposition and interaction of confined spin-waves modes.
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