Publications

Electron Statistical Dynamical Diffuse Scattering in Crystals Containing Short-Range-Order Point Defects

A formal statistical dynamical theory is developed to calculate diffuse scattering produced by short-range order (SRO) in a distorted crystal structure with consideration of atomic thermal vibrations. Diffuse scattering not only produces fine details in diffraction patterns but also introduces a non-local imaginary potential function that reduces the intensities of the Bragg reflected beams. The distribution of the diffusely scattered electrons and the Fourier coefficients of the absorption potential are directly related to a dynamic form factor S(Q,Q′), which has been calculated with consideration of SRO in the distorted lattices. The statistical structure average on imperfections is performed analytically and the final result is correlated to Cowley's short-range-order parameters. The theory is formulated in the Bloch-wave scheme (Bethe theory) for the convenience of numerical calculation in transmission electron diffraction. A rigorous theoretical proof is given to show that the inclusion of a complex potential in the dynamical calculation automatically recovers the contributions made by the high-order diffuse scattering, although the calculation is done using the equation derived for single diffuse scattering. This simply expands the capability of conventional single diffuse scattering theories. Therefore, the complex potential has a much richer meaning than the conventional interpretation of absorption effect.

Z-contrast imaging of bulk crystal surfaces in scanning reflection electron microscopy

Development and progress in piezotronics

Solution Phase Synthesis of Cu(OH)₂ Nanoribbons by Coordination Self-Assembly Using Cu₂S Nanowires as Precursors

Nanoribbons of Cu(OH)2 have been synthesized by coordination self-assembly in solution. Techniques of XRD, TEM, HRTEM, SEM, ED, EDX, and XPS have been used to characterize the morphology, structure, and composition of the nanoribbons. The Cu(OH)2 nanoribbons are 20−100 nm in width, several nm in thickness, and up to 100 μm in length. The basic building blocks of the coordination self-assembly are the square planar complexes of Cu2+, which are continuously supplied in a controlled manner from the Cu2S nanowires. NH3 serves as a molecular transporter in the nanoribbon assembly process. The advantages of our method for the nanoribbon synthesis lie in the low temperature and mild reaction conditions, which permit large scale production at low cost.

Photon‐Memristive System for Logic Calculation and Nonvolatile Photonic Storage

Abstract Memristor‐based architectures have shown great potential for developing future computing systems beyond the era of von Neumann and Moore's law. However, the monotonous electrical input for dynamic resistance regulation limits the developments of memristors. Here, a concept of a photon‐memristive system, which realizes memristance depending on number of photons (optical inputs), is proposed. A detailed theoretical derivation is performed and the memristive characteristics, as stimulated by the optical inputs based on a hybrid system, consisting of a low‐dimension photoelectric semiconductor and a ferroelectric substrate are determined. The photon‐memristive system is also suitable for nonvolatile photonic memory since it possesses three or more‐bit data storage, desirable resistance‐change space, and an ON/OFF ratio of nearly 10 7 . The integrated circuit based on several photon‐memristive systems also realizes available photon‐triggered in‐memory computing. The photon‐memristive system expands the definition of memristors and emerges as a new data storage cell for future photonic neuromorphic computational architectures.

Energy-filtered HREM images of valence-loss electrons

A theory is proposed to include the effects of valence excitations in electron image simulations for high-resolution electron microscopy (HREM) based on the single inelastic scattering model.Under the small thickness approximation, this general theory reduces to the simplified theory of perfectly delocalized inelastic scattering model, in which the image can be considered to be an incoherent sum of those incident electrons of different energies weighted by the intensity distribution in the electron energy-loss spectrum from the area where the pattern was taken.The main effect of valence-loss is to introduce a focus shift due to chromatic aberration, resulting in contrast variation (or reversal) of the image.The generalization of this theory for simulations of interface images with considering surface and interface plasmon excitations is given.Calculations for GaAs surface profile images are demonstrated to show the effect of inelastic localization.

Triboelectric Effect-Driven Liquid Metal Actuators

Owing to the perfect combination of metallic conductivity, liquid fluidity, and mechanical stability, liquid metals (LMs) are considered the potential materials of the electromechanical system and the basic components of liquid robot. Here, triboelectric effect-driven liquid metal actuators (TLMAs) have been demonstrated, in which the motions of LMs could be driven and accurately controlled by triboelectric nanogenerators (TENGs). By the coulomb forces of transferred triboelectric charges in interdigital electrodes and inertia effects, the LM could be driven for continuous linear and circular motions, respectively. As an alternative structure, the motion of LMs could also be accurately controlled, in which the reciprocating and merging of LMs have been demonstrated. Moreover, the TLMA could serve as a control switch to modulate on/off of an LED by integrating into a circuit, and a transport system based on TLMA has also been demonstrated. In this work, the TENG is used as a medium to first drive and accurately control LMs by external mechanical force, which may have great applications in Micro-Electro-Mechanical System (MEMS), liquid robot, and intelligent microcontroller.

Plasma-Enhanced Chemical Vapor Deposition (PECVD)

'Plasma-Enhanced Chemical Vapor Deposition (PECVD)' published in 'Encyclopedia of Nanotechnology'

Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres

Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal rate by 50%, facilitating precise and reliable mass-manufacturing of chips for nanoelectronics. We doped the ceria system with titanium, using flame temperatures that facilitate crystallization of the ceria yet retain the titania in a molten state. In conjunction with molecular dynamics simulation, we show that under these conditions, the inner ceria core evolves in a single-crystal spherical shape without faceting, because throughout the crystallization it is completely encapsulated by a molten 1- to 2-nanometer shell of titania that, in liquid state, minimizes the surface energy. The principle demonstrated here could be applied to other oxide systems.

Flexoelectricity on the photovoltaic and pyroelectric effect and ferroelectric memory of 3D-printed BaTiO3/PVDF nanocomposite

Temperature dependence of pyro-phototronic effect on self-powered ZnO/perovskite heterostructured photodetectors

High-resolution electroluminescent imaging of pressure distribution using a piezoelectric nanowire LED array

Self-powered modulation of elastomeric optical grating by using triboelectric nanogenerator

Performance Optimization of Vertical Nanowire-Based Piezoelectric Nanogenerators

The integrated nanogenerator (NG) based on vertical nanowire (NW) arrays is one of the dominant designs developed to harvest mechanical energy using piezoelectric nanostructures. Finite element method (FEM) simulations of such a NG are developed using ZnO NWs in compression mode to evaluate its performances in term of piezoelectric potential generated, capacitance, induced mechanical energy, output electrical energy, and efficiency. This evaluation is essential to correctly understand NG operation. Three main issues are highlighted. The mechanical and electrical structures of the NG as an integrated system are optimized, and strategies for concentrating the mechanical strain field in the NWs and increasing the force sensitivity are developed. In addition, the influence of NWs length and diameter on NG performances is investigated. The optimization results in a piezoelectric nano composite material where global performances are improved by mean of long and thin NWs.

Properties of Nanobelts and Nanotubes Measured by<i>In Situ</i>TEM

Characterizing the physical properties of individual nanostructures is challenging because of the difficulty in manipulating the objects of sizes from nanometers to micrometers. Most nanomeasurements have been carried using scanning probe microscopy. In this article, we demonstrate that transmission electron microscopy can be a powerful tool for quantitative measurements of the mechanical and electrical properties of a single nanostructure. Dual-mode resonance of an oxide nanobelt has been observed, and its bending modulus has been measured. An in situ technique was demonstrated for measuring the work function at the tip of a carbon nanotube. The ballistic quantum conductance of a multiwalled carbon nanotube was observed at room temperature using the setup in TEM. It is concluded that in situ measurement by directly linking structure with property is a future direction of electron microscopy.

A Self‐Sustainable, Ultrarobust and High‐Power‐Density Triboelectric Nanogenerator for In Situ Powering of Marine Internet of Things

Abstract The sustainable operation of marine Internet of Things (IoT), as a critical enabler for marine resource utilization, is hindered by the lack of robust energy solutions capable of powering advanced functionalities in unpredictable oceanic environments. Here, a self‐sustainable, highly reliable triboelectric nanogenerator system is presented that synergizes a non‐contact architecture with dynamic charge supplementation and multiphase electrode design to overcome persistent limitations in durability, energy storage, and water wave adaptability. The system achieves a 3‐fold enhancement in output charge with 97% performance retention over 20 million cycles—5.2 times more durable than state‐of‐the‐art counterparts. A chaotic double‐pendulum structure further broadens operational bandwidth to 0.4–1.0 Hz with the charge accumulation rate of 4.6 times, enabling record‐breaking average power density of 13.53 W m −3 Hz −1 . Furthermore, an adaptive ultralow‐powered (244 nW) integrated management circuit with on‐demand direct current supply functionality ensures a 394‐fold energy storage speed, successfully sustaining real‐time GPS communication and water quality monitoring in autonomous buoys. This work establishes a scalable, maintenance‐free paradigm for marine energy harvesting, directly addressing the energy paradox in IoT deployment while advancing sustainable resource management and climate resilience strategies.

Degradation of methyl orange by dielectric films based on contact-electro-catalysis

Contact-electro-catalysis (CEC) has been recently proposed for the effective degradation of methyl orange, but the reactivity of catalysts in the CEC process needs further investigation. Here, we have used dielectric films, such as fluorinated ethylene propylene (FEP), modified by inductively coupled plasma (ICP) etching with argon, to replace the previously employed micro-powder due to their potential scalability, facile recycling process, and possible lower generation of secondary pollution. It has been found that ICP creates cone-like micro/nano structures on the surface, and thus changes the contact angle and specific surface area. The value of the contact angle varies non-linearly with etching time and attains a maximum after 60 seconds of etching. Concurrently, an increased electron transfer is observed, as well as an enhanced degradation efficiency, thus suggesting a special role of the surface structure. Finally, KPFM measurements show a lower electron affinity at the summit of the nanocones. This observation suggests that the structures are endowed with higher charge transfer ability. In addition, this film-based CEC has been observed in several polymer materials, such as PET, PTFE, and PVC. We view this work as a stepping stone to develop CEC into scalable applications, based on film technologies.

3D mathematical model of contact-separation and single-electrode mode triboelectric nanogenerators