Nanoscale metal inclusions in or on solid-state dielectrics are an integral part of modern electrocatalysis, optoelectronics, capacitors, metamaterials and memory devices. The properties of these composite systems strongly depend on the size, dispersion of the inclusions and their chemical stability, and are usually considered constant. Here we demonstrate that nanoscale inclusions (for example, clusters) in dielectrics dynamically change their shape, size and position upon applied electric field. Through systematic in situ transmission electron microscopy studies, we show that fundamental electrochemical processes can lead to universally observed nucleation and growth of metal clusters, even for inert metals like platinum. The clusters exhibit diverse dynamic behaviours governed by kinetic factors including ion mobility and redox rates, leading to different filament growth modes and structures in memristive devices. These findings reveal the microscopic origin behind resistive switching, and also provide general guidance for the design of novel devices involving electronics and ionics.

Enriching the functionality of ferroelectric materials with visible-light sensitivity and multiaxial switching capability would open up new opportunities for their applications in advanced information storage with diverse signal manipulation functions. We report experimental observations of robust intralayer ferroelectricity in two-dimensional (2D) van der Waals layered α-InSe ultrathin flakes at room temperature. Distinct from other 2D and conventional ferroelectrics, InSe exhibits intrinsically intercorrelated out-of-plane and in-plane polarization, where the reversal of the out-of-plane polarization by a vertical electric field also induces the rotation of the in-plane polarization. On the basis of the in-plane switchable diode effect and the narrow bandgap (∼1.3 eV) of ferroelectric InSe, a prototypical nonvolatile memory device, which can be manipulated both by electric field and visible light illumination, is demonstrated for advancing data storage technologies.

High-energy nickel (Ni)–rich cathode will play a key role in advanced lithium (Li)–ion batteries, but it suffers from moisture sensitivity, side reactions, and gas generation. Single-crystalline Ni-rich cathode has a great potential to address the challenges present in its polycrystalline counterpart by reducing phase boundaries and materials surfaces. However, synthesis of high-performance single-crystalline Ni-rich cathode is very challenging, notwithstanding a fundamental linkage between overpotential, microstructure, and electrochemical behaviors in single-crystalline Ni-rich cathodes. We observe reversible planar gliding and microcracking along the (003) plane in a single-crystalline Ni-rich cathode. The reversible formation of microstructure defects is correlated with the localized stresses induced by a concentration gradient of Li atoms in the lattice, providing clues to mitigate particle fracture from synthesis modifications.

Interest in the two-dimensional MoS 2 material is consistently increasing because of its many potential applications, in particular in the next-generation nanoelectronic devices. By means of density functional theory computations, we systematically examined the effect of vertical electric field on the electronic structure of MoS 2 bilayer. The bandgaps of the bilayer MoS 2 monotonically decrease with an increasing vertical electric field. The critical electric fields, at which the semiconductor-to-metal transition occurs, are predicted to be in the range of 1.0−1.5 V/Å depending on different stacked conformations. Ab initio quantum transport simulations of a dualgated bilayer MoS 2 channel clearly confirm that the vertical electric field continuously manipulates the transmission gap of bilayer MoS 2 .

We report the electronic structure and optical properties of the recently synthesized stable two-dimensional carbon allotrope-graphdiyne based on first-principles calculations and experimental optical spectrum. Due to the enhanced Coulomb interaction in reduced dimensionality, the band gap of graphdiyne increases to 1.10 eV within the GW many-body theory from a 0.44 eV within the density functional theory. The optical absorption is dominated by excitonic effects with remarkable electron-hole binding energy of over 0.55 eV within the GW-Bethe Salpeter equation calculation. Experimental optical absorption of graphdiyne films is performed and comparison with the theoretical calculations is analyzed in detail.

In thin film ferroelectric devices, switching of ferroelastic domains can significantly enhance electromechanical response. Previous studies have shown disagreement regarding the mobility or immobility of ferroelastic domain walls, indicating that switching behaviour strongly depends on specific microstructures in ferroelectric systems. Here we study the switching dynamics of individual ferroelastic domains in thin Pb(Zr 0.2 ,Ti 0.8 )O 3 films under electrical and mechanical excitations by using in situ transmission electron microscopy and phase-field modelling. We find that ferroelastic domains can be effectively and permanently stabilized by dislocations at the substrate interface while similar domains at free surfaces without pinning dislocations can be removed by either electric or stress fields. For both electrical and mechanical switching, ferroelastic switching is found to occur most readily at the highly active needle points in ferroelastic domains. Our results provide new insights into the understanding of polarization switching dynamics as well as the engineering of ferroelectric devices.

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Supported precious metals with atomic dispersion are of great interest in catalysis due to their potentials in achieving maximum atom efficiency and unique reactivities. Herein, the active sites for low-temperature CO oxidation are elucidated over single-atom Pd1/CeO2 catalysts prepared via high-temperature atom trapping (AT). The increased oxygen vacancies on CeO2 surface induced by 800 °C air calcination result in decreased Pd–CeO2 coordinations, i.e., the coordination-unsaturated Pd2+ on CeO2. Light-off and light-out measurements coupled with CO-DRIFTS and X-ray absorption characterization confirm that these coordination-unsaturated Pd2+ on CeO2 are much more reactive than the fully coordinated counterpart, evidenced by a decrease of T 90 (temperature to achieve 90% conversion) by ∼100 °C in CO oxidation at a gas hourly space velocity of 300 L g–1 h–1.