Jing Zhang

This work investigates the growth of Pt layers down to the monolayer (ML) limit and the subsequent conversion process into PtSe 2 by direct selenization in a molecular beam epitaxy (MBE) environment. The optimum deposition temperature for smooth (111)-oriented, single crystal Pt layers was found to be 300 to 600 °C. A minimal nominal film thickness for full Pt film coverage was determined to be about 3 ML. Optimization of the subsequent reaction with selenium using 3-nm-thick Pt layers to form PtSe 2 was found most efficient at 200 °C. Crystalline PtSe 2 layers with smooth surfaces were formed, but temperature was too low to completely convert the entire 3-nm-thick Pt film. Thinner, uncoalesced Pt films were nearly fully converted into PtSe 2 at 200 °C, but revealed a reduced degree of crystallinity, which was significantly improved by a post-selenization anneal at 400 °C under a Se flux, providing a bottom-up synthesis strategy for PtSe

Nature Nanotechnology, Published online: 06 August 2020; doi:10.1038/s41565-020-0757-7

In the face of the coronavirus pandemic, it is time for the nanotechnology community to shine and build on its experience with nanoscale materials and drug delivery to provide knowledge and tools for COVID-19 vaccine and therapeutics development.

Nature Nanotechnology, Published online: 27 July 2020; doi:10.1038/s41565-020-0743-0

Well-controlled multilayer graphene up to four layers thick with a defined stacking sequence is synthesized via SiC alloy formation on a Cu(111) substrate.

We present a high-resolution resonance Raman study of hBN encapsulated MoSe 2 and WSe 2 monolayers at 4 K using excitation energies from 1.6 eV to 2.25 eV. We report resonances with the WSe 2 A2s and MoSe 2 A2s and B2s excited Rydberg states despite their low oscillator strength. When resonant with the 2s states we identify new Raman peaks which are associated with intravalley scattering between different Rydberg states via optical phonons. By calibrating the Raman scattering efficiency and separately constraining the electric dipole matrix elements, we reveal that the scattering rates for k = 0 optical phonons are comparable for both 1s and 2s states despite differences in the envelope functions. We also observe multiple new dispersive Raman peaks including a peak at the WSe 2 A2s resonance that demonstrates non-linear dispersion and peak-splitting behavior that suggests the dispersion relations for dark excitonic states at ener...

The photoluminescence from aligned 7-atom wide armchair-edge graphene nanoribbons coupled to plasmonic nanoantennas was recently observed to display blinking. Photoluminescence blinking is a hallmark of emission from single quantum emitters. Here we explore the origin of the blinking. We study the influence of the local field enhancement in the vicinity of nanoantennas on the photoluminescence blinking. We observe a clear correlation between the blinking amplitudes and the plasmonic enhancement. For non-resonant metal nanostructures the blinking vanishes almost completely. Our results allow us to conclude that the blinking is an intrinsic feature of the emission from the graphene nanoribbons. This is in contrast to the case of single-molecule surface-enhanced Raman scattering, where it is known that ballistic charge transfer between plasmonic nanoparticles and the molecule under study critically contributes to the blinking.

The chemical/electronic structures of a 2-dimensional (2D) molybdenum disulfide (MoS 2 ) monolayer were characterized using ambient pressure x-ray photoelectron spectroscopy (APXPS) under various gas environments. APXPS results captured the binding energy shifts for the MoS 2 chemical states that represent the electronic-structure of the 2D MoS 2 monolayer in a real gas environment. The effect of the presence of a 2D graphene (Gr) layer on the properties of the 2D MoS 2 layer was simultaneously characterized. When coating a Gr layer on the MoS 2 layer, electron injection from MoS 2 to Gr occurs due to the Schottky barrier at the interface. As a result, the Gr layer and MoS 2 layer attain relatively more n-type and p-type characteristics, respectively, compared to when they exist separately. The hole-injection barrier, formed between the MoS 2 layer and the SiO 2 substrate, is lower by about ...

The nano-devices based on atomic layers of nickel dichalcogenides, including NiS 2 , NiSe 2 and NiTe 2 , are rarely studied due to synthetic problems. Recently, ultrathin NiTe 2 nanosheets are reported to be grown on SiO 2 /Si substrate through chemical vapour deposition (CVD). However, the CVD synthesis of other nickel dichalcogenides is still unknown. Here we report the synthesis of NiSe 2 , NiTe 2 and alloy NiSe 2− x Te x (0 < x < 2) nanosheets through a similar CVD method. We found that the growth temperature has great influences on the shape, size and thickness of as-grown nanosheets. When the growth temperature is about 650 °C, the as-grown NiSe 2 and NiTe 2 nanosheets are as thin as 2.7 nm and 3.1 nm, respectively, which is equal to three layers of crystal unit. Combining the transmission electron microscopy and high-angle annular dark fiel...

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Metal‐organic framework‐derived graphitic porous nanoribbons anchored on graphene sheets are developed as efficient electrodes for electro‐ionic artificial muscles. The actuator exhibits breakthrough bending displacement (17.4 mm), fast rise time (700 ms), wide frequency response (0.1–15 Hz), and excellent cycling stability (92% retention after 25 000 cycles) at 0.5 V input. The actuator is used for successful demonstration of a bio‐mimicked Venus flytrap.

Abstract

To achieve large bending displacement and fast response time under ultralow input voltages, as well as improved durability, advanced high‐performance ionic actuators still face crucial design challenges that must be resolved. Here, hierarchically porous and unzipped graphitic nanoribbons anchored on graphene as an efficient electrode material for high‐performance electroionic artificial muscles are reported. Using controlled solvothermal and pyrolysis methods, nanoarchitectured carbon is derived from a self‐templated potassium‐based metal–organic frameworks–graphene hybrid. The newly designed ionic actuator demonstrates excellent actuation performance, including large bending displacement (17.4 mm) and a strain difference of 0.51% at 0.5 V AC input, very fast response time (700 ms) at 0.5 V DC input, wide frequency response (0.1–15 Hz), and excellent cycling stability (92%) after 25 000 cycles without any delamination of electrodes under continuous electrical operation. The breakthrough in actuation performance mainly stems from the unzipping of hollow nanorods to hierarchical porous graphitic nanoribbons anchored on graphene with the enlarged surface area, large pore volume, stronger mechanical integrity, and emerging charge storage and transport ability. Further, the electroionic actuator shows promise when applied in the demonstration of a biomimicking Venus flytrap.

Concepts of the spin Seebeck effect in ferromagnetic metals have been clarified based on the semi‐classical Boltzmann transport equation including the vital spin‐flip process. The model reveals how it influences the transport equations and provides the relationship between the different spin‐flip relaxation times. Then, the expression of the spin Seebeck coefficient is redefined.

Abstract

Spin Seebeck effect (SSE) and related spin caloritronics have attracted great interest recently. However, the definition of the SSE coefficient remains to be established, let alone a clean experiment to measure the SSE coefficient in ferromagnetic metals. The concept through a model based on the semi‐classical Botlzmann transport equation has been clarified. The model includes the vital spin‐flip process, which is frequent in metals, and points out that the length scale of SSE is much larger than the spin diffusion length. The model reveals how the spin‐flip process influences the transport equations and provides the simple relationship between the different spin‐flip relaxation times for spin‐up and ‐down electrons, which is very useful to understand the spin transport properties. This understanding allows to redefine the expression of the spin Seebeck coefficient.

In article number https://doi.org/10.1002/adfm.2020014832001483, Tongbo Wei, Feng Ding, Peng Gao, Zhongfan Liu, and co‐workers report the direct growth of nano‐patterned graphene on an oxide substrate via selective growth on the c‐plane of a nano‐patterned sapphire substrate, as guided by density functional theory calculations and analogue simulations. The thus obtained nano‐patterned graphene shows potential applications such as high‐performance light‐emitting diodes.

Nature Nanotechnology, Published online: 09 July 2020; doi:10.1038/s41565-020-0724-3

This Review discusses the recent progress and future prospects of two-dimensional materials for next-generation nanoelectronics.

Nature Nanotechnology, Published online: 13 July 2020; doi:10.1038/s41565-020-0733-2

The quantum anomalous Hall state is characterized by a dissipationless chiral edge current. When slightly carrier-doped, Cr-doped (Bi,Sb)2Te3, a magnetic topological insulator, shows current-direction-dependent resistance with a directional difference up to 26%, which probably originates from scattering between the chiral edge state and the Dirac surface state.

In this paper, we for the first time demonstrate efficient nitrogen doping of graphene oxide (GO) with nitrogen concentration of up to almost 5 at.% and desired type of the nitrogen species via modified Hummers’ method. Using x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS) and Fourier transform infrared spectroscopy (FTIR) techniques, we have found out graphitic nitrogen to be the dominant type of the implemented nitrogen species. At the same time, the subsequent GO thermal reduction to graphene appears to result in a transformation of the graphitic nitrogen into pyridines and pyrroles. The mechanisms of the observed GO nitrogen doping and conversion of the nitrogen species are proposed, providing an opportunity to control the type and concentration of the implemented nitrogen within the developed approach. A two-time increase of the graphenes’ conductivity is observed due to the performed nitrogen doping. Further comprehensive electrical studies comb...

A metallic magnet imaged in exquisite detail shows that upon cooling, the new state emerges at the boundaries of the magnetic domains, characteristic of the high‐temperature state, then propagates to the center of the magnetic domains, and expands upon further cooling. The images demonstrate that both states coexist in a large temperature window, which is characteristic of discontinuous transformations.

Abstract

First‐order phase transitions, where one phase replaces another by virtue of a simple crossing of free energies, are best known between solids, liquids, and vapors, but they also occur in a wide range of other contexts, including even elemental magnets. The key challenges are to establish whether a phase transition is indeed first order, and then to determine how the new phase emerges because this will determine thermodynamic and electronic properties. Here it is shown that both challenges are met for the spin reorientation transition in the topological metallic ferromagnet Fe₃Sn₂. The magnetometry and variable temperature magnetic force microscopy experiments reveal that, analogous to the liquid–gas transition in the temperature–pressure plane, this transition is centered on a first‐order line terminating in a critical end point in the field‐temperature plane. The nucleation and growth associated with the transition is directly imaged, indicating that the new phase emerges at the most convoluted magnetic domain walls for the high temperature phase and then moves to self‐organize at the domain centers of the high temperature phase. The dense domain patterns and phase coexistence imply a complex inhomogenous electronic structure, which can yield anomalous contributions to the electrical conductivity.

Artificial ferromagnetic quasicrystals (AMQs) allow spin waves to form nanochannels, which incorporate peculiar sequences of bends, and thus the wavelength of the spin waves is different from nanochannel to nanochannel at a single input frequency. The results suggest that AMQs promise a new class of magnonic devices such as ultra‐compact and dense wavelength division multiplexers.

Abstract

Quasicrystalline structures and aperiodic metamaterials find applications ranging from established consumer gadgets to potential high‐tech photonic components owing to both complex arrangements of constituents and exotic rotational symmetries. Magnonics is an evolving branch of magnetism research where information is transported via magnetization oscillations (magnons). Their control and manipulation are so far best accomplished in periodic metamaterials which exhibit properties artificially modulated on the nanoscale. They give rise to functional components, such as band stop filters, magnonic transistors and nanograting couplers. Here, spin‐wave excitations in artificial ferromagnetic quasicrystals created via aperiodic arrangement of nanoholes are studied experimentally. Their ten‐fold rotational symmetry results in multiplexed magnonic nanochannels, suggesting a width down to 50 nm inside a so‐called Conway worm. Key elements of design are emergent magnon motifs and the worm‐like features which are scale‐invariant and not present in the periodic metamaterials. By imaging wavefronts in quasicrystals, insight is gained into how the discovered features materialize as a dense wavelength division multiplexer.

Nature Nanotechnology, Published online: 02 July 2020; doi:10.1038/s41565-020-0745-y

Publisher Correction: 2D phase transitions: Freezing and melting skyrmions in 2D

The World Health Organization reported that 4.2 million deaths every year were a direct result of exposure to ambient air pollution (NO 2 , SO 2 , NH 3 , CO 2 , CO, CH 4 ). There is a well-demonstrated global need for high sensitivity, low cost and low energy consumption miniaturised gas sensors to be deployed in a dense network and to be used in an attempt to pinpoint and avoid high pollution hot spots. The high sensitivity of graphene to the local environment has shown to be highly advantageous in sensing applications, where ultralow concentrations of adsorbed molecules induce a significant response on the electronic properties of graphene. This is commonly attributed to the π electrons of graphene, being directly exposed to the surrounding environment. The unique electronic structure makes graphene the ‘ultimate’ sensing material for applications in environmental monitoring and air quality. In this review, we present the fro...

An interface engineering method to regulate the interfaces between electrodes and the channels of indium‐gallium‐zinc oxide (IGZO) thin film transistors (TFTs) is demonstrated by bi‐functional acid modification. This method increases the interface oxygen vacancy concentration and reduces the surface roughness, resulting in three‐fold increased mobility and reduces contact resistance by 75%.

Abstract

Solution‐processed indium‐gallium‐zinc oxide (IGZO) thin film transistors (TFTs) have become well known in recent decades for their promising commercial potential. However, the unsatisfactory performance of small‐sized IGZO TFTs is limiting their applicability. To address this issue, this work introduces an interface engineering method of bi‐functional acid modification to regulate the interfaces between electrodes and the channels of IGZO TFTs. This method increases the interface oxygen vacancy concentration and reduces the surface roughness, resulting in higher mobility and enhanced contact at the interfaces. The TFT devices thus treated display contact resistance reduction from 9.1 to 2.3 kΩmm, as measured by the gated four‐probe method, as well as field‐effect mobility increase from 1.5 to 4.5 cm² (V s)⁻¹. Additionally, a 12 × 12 organic light emitting diode display constructed using the acid modified IGZO TFTs as switching and driving elements demonstrate the applicability of these devices.

Atomically thin 1T‐TaSe₂ crystals are grown on SiO₂/Si substrates by chemical vapor deposition. A commensurate charge density wave transition temperature of 570 K is observed in 3 nm thick 1T‐TaSe₂, which is 97 K higher than in previously reported bulk samples.

Abstract

Bulk 1T‐TaSe₂ as a charge‐density‐wave (CDW) conductor is of special interest for CDW‐based nanodevice applications because of its high CDW transition temperature. Reduced dimensionality of the strongly correlated material is expected to result in significantly different collective properties. However, the growth of atomically thin 1T‐TaSe₂ crystals remains elusive, thus hampering studies of dimensionality effects on the CDW of the material. Herein, chemical vapor deposition (CVD) of atomically thin TaSe₂ crystals is reported with controlled 1T phase. Scanning transmission electron microscopy suggests the high crystallinity and the formation of CDW superlattice in the ultrathin 1T‐TaSe₂ crystals. The commensurate–incommensurate CDW transition temperature of the grown 1T‐TaSe₂ increases with decreasing film thickness and reaches a value of 570 K in a 3 nm thick layer, which is 97 K higher than that of previously reported bulk 1T‐TaSe₂. This work enables the exploration of collective phenomena of 1T‐TaSe₂ in the 2D limit, as well as offers the possibility of utilizing the high‐temperature CDW films in ultrathin phase‐change devices.

A new van der Waals ferromagnet AgVP₂Se₆ is discovered and successfully synthesized. The AgVP₂Se₆ flakes exhibit significant thickness‐dependent magnetic properties, and a rectangular hysteresis loop with a large coercive field of 750 Oe at 2 K and an undiminished Curie temperature of 19 K are observed in the 6.7 nm flake.

Abstract

The recent realization of 2D magnetism in van der Waals (vdWs) magnets holds promise for future information technology. However, the vdWs semiconducting ferromagnets, which remain rare, are especially important in developing 2D magnetic devices with new functionalities due to the possibility of simultaneous control of the carrier charge and spin. Metal thiophosphate (MTP), a multifunctional vdWs material system that combines the sought‐after properties of complex oxides, is a promising vdWs magnet system. Here, single crystals of a novel vdWs ferromagnetic semiconductor MTP AgVP₂Se₆ with a room‐temperature resistivity of 1 Ω m are successfully synthesized. Due to the nature of vdWs bonding along the c‐axis, the magnetic properties of the few‐layer AgVP₂Se₆ with different thicknesses are characterized on the exfoliated samples. The AgVP₂Se₆ flakes exhibit significant thickness‐dependent magnetic properties, and a rectangular hysteresis loop with a large coercive field of 750 Oe at 2 K and an undiminished Curie temperature of 19 K are observed in the 6.7 nm AgVP₂Se₆ flake. The discovered vdWs ferromagnet AgVP₂Se₆ with semiconducting behavior will provide alternative platforms for exploring 2D magnetism and potential applications in spintronic devices.

A versatile mechanoplastic artificial synapse composed of a floating‐gate MoS₂ synaptic transistor integrated with a triboelectric nanogenerator is proposed, which utilizes mechanical displacement to realize synaptic plasticity. Based on the mechanoplastic artificial synapse, typical synaptic plasticity behaviors (potentiation/inhibition and paired pulse facilitation/depression) and artificial neural network are successfully imitated.

Abstract

The emulation of synaptic plasticity to achieve sophisticated cognitive functions and adaptive behaviors is critical to the evolution of neuromorphic computation and artificial intelligence. More feasible plastic strategies (e.g., mechanoplasticity) are urgent to achieve comparable, versatile, and active cognitive complexity in neuromorphic systems. Here, a versatile mechanoplastic artificial synapse based on tribotronic floating‐gate MoS₂ synaptic transistors is proposed. Mechanical displacement can induce triboelectric potential coupling to the floating‐gate synaptic transistor, trigger a postsynaptic current signal, and modulate the synaptic weights, which realizes the synaptic mechanoplasticity in an active and interactive way. Typical synaptic plasticity behaviors including potentiation/inhibition and paired pulse facilitation/depression are successfully imitated. Assistant with the charge trapping by floating gate, the artificial synapse can realize mechanical displacement derived short‐term and long‐term plasticity simultaneously. A facile artificial neural network is also constructed to demonstrate an adding synaptic weight and neuromorphic logic switching (AND, OR) by mechanoplasticity without building complex complementary metal oxide semiconductor circuits. The proposed mechanoplastic artificial synapse offers a favorable candidate for the construction of mechanical behavior derived neuromorphic devices to overcome the von Neumann bottleneck and perform advanced synaptic behaviors.

Antisite defect engineering is introduced as a powerful strategy to effectively engineer band structure, resulting in optimally enhanced thermoelectric performance of SnTe while simultaneously preserving its topological nature. The present study sheds new light on the inherent ties between the thermoelectric and topological properties of various materials.

Abstract

As the first experimentally established topological crystalline insulator (TCI), SnTe also exhibits superior thermoelectricity upon proper doping; yet to date, whether such doping will preserve or destroy the salient topological properties in achieving outstanding thermoelectric (TE) performance remains elusive. Using first‐principles calculations combined with Boltzmann transport theory, here the elegant role of antisite defect in optimally enhancing the thermopower of SnTe while simultaneously preserving its topological nature is uncovered. It is first shown that Sn_Te antisite defect effectively induces pronounced variations in the low‐energy density of states rather than rigidly shifting the chemical potential, resulting in a higher Seebeck coefficient and power factor. Next, it is demonstrated that in a wide temperature range, the Seebeck coefficient of antisite‐doped SnTe distinctly outperforms previously identified systems invoking extrinsic dopants. It is further confirmed that such intrinsic antisite doping preserves the nontrivial topology, which in turn favors high electrical conductivity and thermoelectricity. These central findings not only identify an effective and powerful knob in future studies of TE materials, but also help to resolve standing controversies between theory and experiment surrounding the TE performances of both TCIs and topological insulators.

Electric field‐induced oxygen motion (magneto‐ionics) could make a significant breakthrough in low‐power magnetically actuated devices. By applying electric fields using an electrochemical capacitor instead of a transistor‐like configuration, room‐temperature magneto‐ionic switching speed and magnetization in electrolyte‐gated paramagnetic Co₃O₄ films can be largely increased. This might widen the use of magneto‐ionics in technological applications such as neuromorphic computing or iontronics.

Abstract

Voltage control of magnetism through electric field‐induced oxygen motion (magneto‐ionics) could represent a significant breakthrough in the pursuit for new strategies to enhance energy efficiency in magnetically actuated devices. Boosting the induced changes in magnetization, magneto‐ionic rates and cyclability continue to be key challenges to turn magneto‐ionics into real applications. Here, it is demonstrated that room‐temperature magneto‐ionic effects in electrolyte‐gated paramagnetic Co₃O₄ films can be largely increased both in terms of generated magnetization (6 times larger) and speed (35 times faster) if the electric field is applied using an electrochemical capacitor configuration (utilizing an underlying conducting buffer layer) instead of placing the electric contacts at the side of the semiconductor (electric‐double‐layer transistor‐like configuration). This is due to the greater uniformity and strength of the electric field in the capacitor design. These results are appealing to widen the use of ion migration in technological applications such as neuromorphic computing or iontronics in general.

The applications of 2D MXene‐based materials in electrocatalysis, including hydrogen evolution reaction, nitrogen reduction reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and methanol oxidation reaction as well as the current safer and more environmentally friendly preparation methods of MXenes are summarized and discussed in this review.

Abstract

The family of transition metal carbides, nitrides, and carbonitrides (collectively called MXenes) has been a thriving field since the first invention of Ti₃C₂T _x (MXene) in 2011. MXene is a new type of nanometer 2D sheet material, which exhibits great application potentials in various fields due to its multiple advantages such as high specific surface area, good electrical conductivity, and high mechanical strength. Electrocatalysis is regarded as the core of future clean energy conversion technologies, and MXene‐based materials provide inspiration for the design and preparation of electrocatalysts with high activity, high selectivity, and long loading life time. The applications of MXene‐based materials in electrocatalysis, including hydrogen evolution reaction, nitrogen reduction reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and methanol oxidation reaction are summarized in this review. As a crucial session regarding experiments, the current safer and more environmentally friendly preparation methods of MXene are also discussed. Focusing on the materials design and enhancement methods, the key challenges and opportunities for MXene‐based materials as a next‐generation platform in both fundamental research and practical electrocatalysis applications are presented. This account serves to promote future efforts toward the development of MXenes and related materials in the electrocatalysis applications.

Identifying catalytically active sites and clarifying structure–activity relationships are critical to synthesize efficient electrocatalysts for various energy conversion technologies. Herein, a comprehensive review of recent progresses on this attractive topic with the assistance of advanced characterization techniques is provided. Current challenges and future directions are discussed to guide the rational design of electrocatalysts with outstanding activity, selectively, and durability.

Abstract

Highly efficient electrocatalysts play an integral part in developing renewable energy conversion and storage technologies. Despite considerable efforts devoted to synthesizing electrocatalysts with superior performance, the identification of active moieties and understanding of reaction mechanisms under practical conditions still remain elusive. Herein, the substantial progresses in unraveling the local electronic and atomic structure optimizations of nanocatalysts for gas‐involved electrocatalysis, disclosing real active sites, and clarifying their relationships with intrinsic activities by combining advanced characterization techniques with computational simulations are summarized. The continuous development of in situ and ex situ characterization tools, particularly at multi‐scale resolution, to monitor or even directly observe the active center structure is systematically discussed, which is divided into four main categories based on the type of active sites: atomically dispersed active sites, vacancies, heteroatom doping sites, and edge sites. Current challenges and perspectives in both fundamental area and industrial application are finally proposed for the future research direction of next‐generation electrode materials. The aim of this review is to provide mechanistic insights into the real catalytically active structure with the assistance of newly developed characterization techniques, guiding the rational design and structure engineering of advanced functional materials with outstanding activity, selectivity, and durability.

New optical phase‐change materials are demonstrated, with the ability to realize on‐chip programmable phase control with very low optical losses. The chalcogenides Sb₂S₃ and Sb₂Se₃ exhibit a large refractive index contrast between their crystalline and amorphous phases. With reversible switching over thousands of cycles and easy integration with silicon, these materials pave the way for low‐loss reconfigurable and programmable nanophotonics.

Abstract

Phase‐change materials (PCMs) are seeing tremendous interest for their use in reconfigurable photonic devices; however, the most common PCMs exhibit a large absorption loss in one or both states. Here, Sb₂S₃ and Sb₂Se₃ are demonstrated as a class of low loss, reversible alternatives to the standard commercially available chalcogenide PCMs. A contrast of refractive index of Δn = 0.60 for Sb₂S₃ and Δn = 0.77 for Sb₂Se₃ is reported, while maintaining very low losses (k < 10⁻⁵) in the telecommunications C‐band at 1550 nm. With a stronger absorption in the visible spectrum, Sb₂Se₃ allows for reversible optical switching using conventional visible wavelength lasers. Here, a stable switching endurance of better than 4000 cycles is demonstrated. To deal with the essentially zero intrinsic absorption losses, a new figure of merit (FOM) is introduced taking into account the measured waveguide losses when integrating these materials onto a standard silicon photonics platform. The FOM of 29 rad phase shift per dB of loss for Sb₂Se₃ outperforms Ge₂Sb₂Te₅ by two orders of magnitude and paves the way for on‐chip programmable phase control. These truly low‐loss switchable materials open up new directions in programmable integrated photonic circuits, switchable metasurfaces, and nanophotonic devices.

When a dynamic crack front travels through material heterogeneities, elastic waves are emitted, which perturb the crack and change the morphology of the fracture surface. For asperity-free crystalline materials, crack propagation along preferential cleavage planes is expected to present a smooth crack front and form a mirror-like fracture surface. Surprisingly,...

Earth-abundant oxygen evolution catalysts (OECs) with extended stability in acid can be constructed by embedding active sites within an acid-stable metal-oxide framework. Here, we report stable NiPbOx films that are able to perform oxygen evolution reaction (OER) catalysis for extended periods of operation (>20 h) in acidic solutions of pH...

Metal and dielectric have long been thought as two different states of matter possessing highly contrasting electric and optical properties. A metal is a material highly reflective to electromagnetic waves for frequencies up to the optical region. In contrast, a dielectric is transparent to electromagnetic waves. These two different classical...