Abstract Defects play a vital role in understanding and elucidating the structure-property relationship in materials science. Here we report the existence of a new kind of planar defect, filling fault, in half-Heusler (HH) compounds—a structurally and functionally diverse family of materials. The ideal HH structure is composed of three occupied and one vacant sublattices. The two-dimensional filling fault layer tends to form with the originally vacant 4d sites occupied, fully or partly, which results in a vacancy swap occupation between the 4c and 4d sublattices. It is found that the filling faults are apt to form fully in Ni-based ZrNiSn and ScNiSb, moderately in Co-based TiCoSb, and hardly in Fe-based NbFeSb and VFeSb. The unique defect configurations and the formation rule clarify the long-standing structure puzzles in HH compounds. Furthermore, we find that the filling faults and associated vacancy swap occupation can significantly enhance the piezoelectricity and change the temperature dependence of electrical conductivity. These results deepen the understanding of precise crystallographic structures and defect-property relationships in solids, and facilitate the design of advanced materials and functional devices.

As a ubiquitous substance in nature, ice has attracted substantial research interest across a variety of fields, including physics, environmental science, biology, and cryopreservation. However, the intricate structural transformations within ice remain elusive owing to the stringent experimental constraints. Herein, the detailed evolution of ice nanopores, including expansion and healing, is investigated using advanced cryo-electron microscopy combined with low-dose techniques, and the underlying mechanisms are revealed through surface-free energy analysis. Three pivotal factors are identified as driving the evolution mechanism of ice nanopores: the nanopore geometry and dimensions and the thickness of the ice film. This research not only provides novel insights into the dynamic structural evolution of ice at the molecular scale but also paves the way for a deeper understanding of the fundamental properties and behaviors of ice. Moreover, the healing mechanism of the nanopores is anticipated to be utilized in ice manipulation and nanofabrication.

The utilization of thermoelectric (TE) technology for eco-friendly energy harvesting presents a promising solution for off-grid power generation from waste heat.

Metal-semiconductor contacts play a pivotal role in controlling carrier transport in the fabrication of modern electronic devices. The exploration of van der Waals (vdW) metal contacts in semiconductor devices can potentially mitigate Fermi-level pinning at the metal-semiconductor interface, with particular success in two-dimensional layered semiconductors, triggering unprecedented electrical and optical characteristics. In this work, for the first time, we report the direct integration of vdW metal contacts with bulk wide bandgap gallium nitride (GaN) by employing a dry transfer technique. High-angle annular dark-field scanning transmission electron microscopy explicitly illustrates the existence of a vdW gap between the metal electrode and GaN. Strikingly, compared with devices fabricated with electron beam-evaporated metal contacts, the vdW contact device exhibits a responsivity two orders of magnitude higher with a significantly suppressed dark current in the nanoampere range. Furthermore, by leveraging the high responsivity and persistent photoconductivity obtained from vdW contact devices, we demonstrate imaging, wireless optical communication, and neuromorphic computing functionality. The integration of vdW contacts with bulk semiconductors offers a promising architecture to overcome device fabrication challenges, forming nearly ideal metal-semiconductor contacts for future integrated electronics and optoelectronics.

The transformation from amorphous materials to crystals and the corresponding microscopic mechanism have become a research focus in materials science, condensed matter physics, and biophysics etc. In this paper, taking Y3Al5O12 (YAG) as an example, the crystallization process of amorphous YAG oxide is investigated from an atomic point of view through the combination of spherical aberration-corrected transmission electron microscopy (SCTEM) with an in situ heating method, and the morphology and structural evolution of the surface and interface are explored. It is observed that the crystallization proceeds on the surface and interior of the amorphous YAG separately. Through atomic-scale imaging, it is determined that semi-ordered structures are formed in a few atomic layers at the amorphous/crystalline interface and that the structural transformation process from the amorphous to the semi-ordered state and then to the crystal structure may be the main reason for the multiple stages of the crystallization of amorphous oxides. This study demonstrates the mechanism of the amorphous-to-crystal transformation on the atomic scale and contributes to gaining a better understanding of the crystallization process of bulk oxides, especially complex metal oxides.

Electrode contact interfaces for practical thermoelectric (TE) devices require high bonding strength, low specific contact resistivity, and superb stability. Herein, the state‐of‐the‐art Cu 2 MgFe/Mg 2 Sn 0.75 Ge 0.25 interface is designed for Mg 2 Sn 0.75 Ge 0.25 ‐based TE devices, adhering to the general strategy of high bonding propensity, thermal expansion matching, diffusion passivation, and dopant inactivation. The interfacial stability is verified by the in situ transmission electron microscopy analysis, thereby confirming the contributions from decreasing the chemical potential gradient and increasing the diffusion activation energy barrier. The single‐leg device exhibits a high power density ( ω max ) of 2.6 W cm −2 and conversion efficiency ( η max ) of 8% under a temperature difference (Δ T ) of 370 °C, which is the record‐breaking value in comparison to other Mg 2 (Si, Ge, Sn)‐based TE devices. Additionally, a two‐couple device with p ‐type Bi 2 Te 3 shows an excellent ω max of 1.3 W cm −2 and η max of 5.4% under a Δ T of 270 °C, comparable to commercial Bi 2 Te 3 devices. The proposed interface design strategy provides a general technique for constructing high‐performance devices using cutting‐edge TE materials.

Scanning moiré fringes (SMFs) in scanning transmission electron microscopy (STEM) have a broad application prospect owing to the low-magnification imaging and hereto the low electron irritation damage, especially in defects localization, strain analysis etc. However, the dynamic evolution mechanism of SMFs is still not clear. In this paper, we carry out in-depth study of SMFs with ferroelectric material GeSe as an example. With the help of combination of aberration-corrected STEM imaging and geometrical model, we discuss the evolution of SMFs with variation of scanning step (magnification), and explain its quasiperiodic behavior in the experiments. Our results will deepen the understanding of SMFs, and may widen their applications under the guidance of the new formation mechanism.

The thermal stability of the electrode interface is always a critical concern in the long-term service of thermo-electric power generators (TEGs). This work has systematically investigated the thermal stability of the interfaces of Ni/Bi(2)Te(2.7)Se(0.3)and Ni/Bi0.4Sb1.6Te3 of the Bi2Te3-based Thermoelectric generator (TEG) device by using high-resolution transmission electron microscopy (HRTEM) with in-situ heating technique. Kirkendall voids (KVs) were directly observed in the electrode interfaces of both Ni/Bi2Te2.7Se0.3 and Ni/Bi0.4Sb1.6Te3, providing thus the microscopic reason for the naked-eye cracks causing thermal failure. The growth of KVs of the as -investigated interfaces shows multi-stage behavior. This effect is attributed to the superimposition of vacancy coalesce due to the interdiffusion and interface stress mechanisms owing to the plastic difference and volume shrinkage relative to the interface reaction. Among the various interface reactions, the reaction of 3Ni + 2Bi2Te3 = 3NiTe2 + 4Bi has the largest volume shrinkage, and hence decisively affects the growth of KVs. An outlook relative to the design of the thermal stability is also provided from the point of view of reducing the local stress to suppress the formation of KVs, which is regarded as a valuable guideline for the electrode interface design of TEGs.

Bi2Te3-based thermoelectric materials are widely used in solid-state refrigeration near room temperature. However, the room temperature figure of merit (zT) of n-type Bi2Te3-based polycrystals produced by once sintering is always lower than 0.8. Herein, low-angle grain boundaries (LAGBs) are introduced in n-type Bi2Te2.7+xSe0.3 by a simple step-hot-pressing procedure (once sintering) and well characterized by scanning transmission electron microscopy. LAGBs consist of dislocation arrays that can effectively scatter the medium-frequency phonons and thus suppress the lattice thermal conductivity. Although LAGBs also serve as scattering centers of low-energy electrons and deteriorate the carrier mobility, they could contribute to the enhanced Seebeck coefficient owing to the increased scattering factor. Overall, the samples with LAGBs own lower electronic thermal conductivity at the same power factor level. Finally, a high room temperature zT of 0.94 is obtained in n-type Bi2Te2.7Se0.3, which is comparable to those produced by multiple-time sintering. Moreover, step-hot-pressing is also found to be effective in promoting the room temperature zT of p-type Bi2Te3-based polycrystals. This work puts forward a new and simple method to construct LAGBs in Bi2Te3-based alloys that enhances their zTs, and sheds light on the underlying mechanisms about how the LAGB affects the electrical and thermal transport properties.

Carbon dots (CDs) have received tremendous attention for their excellent photoluminescence (PL) properties. However, it remains a great challenge to obtain CDs with ultraviolet (UV, 200-400 nm) emission in solid state, which requires strict control of the CDs structure and overcoming the aggregation-caused quenching (ACQ). Herein, a new sp3 compartmentalization strategy is developed to meet these requirements, by employing acetic acid to promote fractions of sp3 bonding during the synthesis of CDs. It markedly decreases the size of sp2 conjugating units in the CDs, and shifts PL emission to the ultraviolet B (UVB) region (λmax  = 308 nm). Moreover, sp2 domains are well spatially compartmentalized by sp3 domains and the ACQ effect is minimized, enabling the high quantum yield in solid state (20.2%, λex  = 265 nm) with a narrow bandwidth of 24 nm and environmental robustness. The solid-state UVB emissive CDs are highly desired for application in photonic devices. Hence, a demo of UVB light-emitting diodes is fabricated for plant lighting, leading to a 29% increase of ascorbic acid content in the basil. Overall, a rational and efficient way to construct solid UVB-CDs phosphors for wide applications is provided.

PdZn ss alloy catalysts have Cu-like properties for a wide range of industrially important reactions, such as methanol synthesis, water-gas shift, and methanol steam reforming, but overcome the major disadvantages inherited by Cu such as sintering and pyrophoric nature. However, high Pd loadings (e.g., >5.0 wt %) are typically required for the synthesis of the PdZn beta alloy, preventing its practical consideration as the replacement of Cu catalysts. Here, we report the synthesis of ZnAl2O4-supported PdZn beta alloy catalysts at extremely low Pd loadings (e.g., 1000 ppm Pd). In particular, a cuboctahedral ZnAl2O4 spinel support with exclusively polar facets provides a strong interaction between Pd and Zn, leading to PdZn beta alloy formation even at low Pd loadings. A 0.1 wt % Pd/ZnAl2O4 catalyst is shown to exhibit superior CO2 selectivity (97%) in the methanol steam reforming reaction, confirming the Cu-like catalytic properties of the PdZn beta alloy even at 1000 ppm Pd. The top-layer Zn species on the exposed polar facets of zinc spinel were found to play a critical role in the preferential formation of the PdZn beta alloy. The advances toward the PdZn beta alloy catalysts with extremely low Pd loadings bring the PdZn alloy catalysts one step closer to a wide range of applications.

Currently, Cu2GeS3 has been obtained through solid-state reaction. However, the pure phase Cu2GeS3 synthesized still faces challenges due to the low boiling point of the sulfur element. Herein, we have prepared pristine Cu2GeS3 by a two-step method. Firstly, the pure phase GeS2 was synthesized by solvothermal method and then used the freshly as-synthesized GeS2 as raw material to react with copper powder to fabricate pure phase Cu2GeS3. Further, the thermoelectric properties of Cu2GeS3 crystal have been explored. At room temperature, the electric resistance value measured by multimeter was ~ 2634 Ω for intrinsic Cu2GeS3 crystal, which exceeded the instrument (electrical conductivity/Seebeck coefficient) test range of 0–2000 Ω, so there is no relevant report in the thermoelectric field about Cu2GeS3 crystal. In order to improve its conductivity, Cu2GeS3 crystal is alloyed with a small amount of Te powder to obtainable Cu2GeS3−xTex samples, which have obvious thermoelectric properties. By adjusting the content of Te, finally, the electrical conductivity of the Cu3GeS2.6Te0.4 sample reached 364.20 S m−1 and the figure-of-merit ZTmax value of ~ 0.12 were obtained at 816 K.

The structure of thermoelectric materials largely determines the thermoelectric characteristics. Hence, a better understanding of the details of the structural transformation process/conditions can open doors for new applications. In this study, the structural transformation of PbTe (a typical thermoelectric material) is studied at the atomic scale, and both nucleation and growth are analyzed. We found that the phase transition mainly occurs at the surface of the material, and it is mainly determined by the surface energy and the degree of freedom the atoms have. After exposure to an electron beam and high temperature, high-density crystal-nuclei appear on the surface, which continue to grow into large particles. The particle formation is consistent with the known oriented-attachment growth mode. In addition, the geometric structure changes during the transformation process. The growth of nanoparticles is largely determined by the van der Waals force, due to which adjacent particles gradually move closer. During this movement, as the relative position of the particles changes, the direction of the interaction force changes too, which causes the particles to rotate by a certain angle.

The structure of thermoelectric materials largely determines the thermoelectric characteristics. Hence, a better understanding of the details of the structural transformation process/conditions can open doors for new applications. In this study, the structural transformation of PbTe (a typical thermoelectric material) is studied at the atomic scale, and both nucleation and growth are analyzed. We found that the phase transition mainly occurs at the surface of the material, and it is mainly determined by the surface energy and the degree of freedom the atoms have. After exposure to an electron beam and high temperature, highdensity crystal-nuclei appear on the surface, which continue to grow into large particles. The particle formation is consistent with the known oriented-attachment growth mode. In addition, the geometric structure changes during the transformation process. The growth of nanoparticles is largely determined by the van der Waals force, due to which adjacent particles gradually move closer. During this movement, as the relative position of the particles changes, the direction of the interaction force changes too, which causes the particles to rotate by a certain angle.

Realizing high‐temperature thermal stability in thermoelectric (TE) generators is a critical challenge. In this study, a synergistic interface and surface optimization strategy is implemented to enhance Mg3Sb1.5Bi0.5 TE generator performance by employing FeCrTiMnMg thermoelectric interface materials and the MgMn‐based alloy protective coating. The competitive output power density (ω) of 1.7 W cm−2 and a conversion efficiency (η) of 13% for the single‐leg device are achieved at hot‐side temperature (Th) and cold‐side temperature (Tc) of 500 and 5 °C, respectively. An ω of 0.8 W cm−2 and η of 6% for the two‐couple TE devices with p‐type commercial Bi2Te3 are also realized, values that are competitive with the commercial Bi2Te3 device. Additionally, the single‐leg device shows a high stable η for over 100 h when the Th and Tc are 400 and 5 °C, respectively, with an change rate (Δηmax/ηmax,o) of <3%. In situ transmission electron microscopy analysis further reveals that the high stability results from the effectively sluggish interdiffusion and reduced Mg evaporation that decrease the chemical potential gradient, reduce the saturated vapor pressure, and increase the diffusion activation energy barrier. This study provides a general technique route for boosting the high‐temperature thermal stability of TE generator.

The traditional 3D porous structures often sacrifice density for high porosity, which is not conducive for energy storage under a limited space. So, it is a challenge to seek the strategy to well balance of the density and porosity in foam materials. In this work, we fabricated MXene based foam by the hydrazine vapor-induced reduction, which can achieve the precise regulation on the density (100-360 mg cm-3) and pore size (5.08-61.04 mu m) while maintaining its high porosity over 77.9%. And it is carried out by simply tuning the oxygenated functional group concentration of the original MXene/GO films. Then the interlayer-spacing-regulated 3D MXene/rGO foams was used to construct the multifunctional Zinc ion microcapacitor (ZIMC) by the laser engraving processes, which is simple and suitable for large-scale process production. The final ZIMC exhibited a low self-discharge rate of 2.75 mV h-1, a large area-specific capacitance of 83.96 mF cm-2, and maintained an initial capacitance of 86.3% after five self-healing processes. In addition, the ZIMC-powered integrated pressure sensing system enables real-time monitoring of human physiological signals. Combining these prominent performance with the simple deviceassembly method makes this microcapacitor highly potential in the next-generation electronics.

High-speed operation and low-power-consumption requirements have accelerated the development of thin-film transistors (TFTs) with exploration of gate dielectrics. In this work, the integration of all-sputtering-derived HfGdO high-k gate dielectrics with amorphous InGaZnO (a-InGaZnO) films has been reported, yielding significant improvements in the performance of a-InGaZnO TFTs. By adjusting the multilayer dielectric sequence, TFT device performance can be precisely manipulated. It has been detected that a-InGaZnO TFTs with an optimized Al2O3 /HfGdO dielectric configuration have demonstrated superior electrical performance, including a high field-effect mobility (mu(FE)) of 23.3 cm(2).V-1.S-1, a large on/off current ratio of 1.2 x 10(7), a low subthreshold swing of 0.09 V/dec, and good stability under bias stress. Finally, a low-voltage-operated resistor-loaded unipolar inverter has been assembled on the base of Al2O3/HfGdO/a-InGaZnO TFTs, demonstrating full swing characteristics and high gain of similar to 20. All of the experimental results indicate promising potentials for all-sputtering-derived Al2O3/HfGdO laminated dielectrics toward the achievement of low-cost, low-power-consumption, and large-area all-oxide optoelectronics.

Energy-saving photodetectors are the key components in future photonic systems. Particularly, self-powered photoelectrochemical-type photodetectors (PEC-PDs), which depart completely from the classical solid-state junction device, have lately intrigued intensive interest to meet next-generation power-independent and environment-sensitive photodetection. Herein, we construct, for the first time, solar-blind PEC PDs based on self-assembled AlGaN nanostructures on silicon. Importantly, with the proper surface platinum (Pt) decoration, a significant boost of photon responsivity by more than an order of magnitude was achieved in the newly built Pt/AlGaN nanoarchitectures, demonstrating strikingly high responsivity of 45 mA/W and record fast response/recovery time of 47/20 ms without external power source. Such high solar-blind photodetection originates from the unparalleled material quality, fast interfacial kinetics, as well as high carrier separation efficiency which suggests that embracement of defect-free wide-bandgap semiconductor nanostructures with appropriate surface decoration offers an unprecedented opportunity for designing future energy-efficient and large-scale optoelectronic systems on a silicon platform.