Jiuxiang Dai

Although research on low-dimensional nanomaterials has been booming for decades, more research is needed on how to utilize them to construct efficient information sensing, processing, and feedback devices. A review of recent representative studies on information sensing, processing, and feedback devices based on low-dimensional nanomaterials to provide a perspective on developing human–machine–thing natural interaction technologies is presented.

Abstract

A wide variety of low-dimensional nanomaterials with excellent properties can meet almost all the requirements of functional materials for information sensing, processing, and feedback devices. Low-dimensional nanomaterials are becoming the star of hope on the road to pursuing human–machine–thing natural interactions, benefiting from the breakthroughs in precise preparation, performance regulation, structural design, and device construction in recent years. This review summarizes several types of low-dimensional nanomaterials commonly used in human–machine–thing natural interactions and outlines the differences in properties and application areas of different materials. According to the sequence of information flow in the human–machine–thing interaction process, the representative research progress of low-dimensional nanomaterials-based information sensing, processing, and feedback devices is reviewed and the key roles played by low-dimensional nanomaterials are discussed. Finally, the development trends and existing challenges of low-dimensional nanomaterials in the field of human–machine–thing natural interaction technology are discussed.

Simple twisted stacking of two layers of nanomaterials can produce ultrathin planarized nanostructures with optical chirality. This review thoroughly examines the recent progress in ultrathin chiroptical metasurfaces prepared through chiral stacking, discussing the monolayer materials, fabrication strategies, and the induced circular dichroism. A special focus is placed on the flexible tunability of the chiroptical responses and relevant optical applications.

Abstract

Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on-chip integration and improved energy efficiency as polarization-sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der Waals materials, ultrathin films, or traditional metasurfaces, at an angle has emerged as a general strategy to introduce optical chirality into achiral solid-state systems. This method endows new degrees of freedom, e.g., the interlayer twist angle, to flexibly engineer and tune the chiroptical responses without having to change the material or the design, thus greatly facilitating the development of multifunctional metamaterials. In this review, recent exciting progress in planar chiral metasurfaces are summarized and discussed from the viewpoints of building blocks, fabrication methods, as well as circular dichroism and modulation thereof in twisted stacked nanostructures. The review further highlights the ever-growing portfolio of applications of these chiral metasurfaces, including polarization conversion, information encryption, chiral sensing, and as an engineering platform for hybrid metadevices. Finally, forward-looking prospects are provided.

With Ag₁₈Cu₃Te₁₁Cl₃, a material for the first one-compound diode is discovered. A temperature-gradient driven pn-junction is realized in a single crystal where p- and n-type conduction is accessed without external doping. The transition close to room temperature enables a variety of semiconductor applications.

Abstract

A diode requires the combination of p- and n-type semiconductors or at least the defined formation of such areas within a given compound. This is a prerequisite for any IT application, energy conversion technology, and electronic semiconductor devices. Since the discovery of the pnp-switchable compound Ag₁₀Te₄Br₃ in 2009, it is in principle possible to fabricate a diode from a single material without adjusting the semiconduction type by a defined doping level. Often a structural phase transition accompanied by a dynamic change of charge carriers or a charge density wave within certain substructures are responsible for this effect. Unfortunately, the high pnp-switching temperature between 364 and 580 K hinders the application of this phenomenon in convenient devices. This effect is far removed from a suitable operation temperature at ambient conditions. Ag₁₈Cu₃Te₁₁Cl₃ is a room temperature pnp-switching material and the first single-material position-independent diode. It shows the highest ever reported Seebeck coefficient drop that takes place within a few Kelvin. Combined with its low thermal conductivity, it offers great application potential within an accessible and applicable temperature window. Ag₁₈Cu₃Te₁₁Cl₃ and pnp-switching materials have the potential for applications and processes where diodes, transistors, or any defined charge separation with junction formation are utilized.

The authors present recent advances to develop a wide spectrum of molecular heterostructures, as well as their prospects and applicability. Various molecular heterostructures and their novel electrical characteristics, along with their charge transport mechanisms are presented. In addition, the potential applicability, merits, and perspectives, as well as the anticipated challenges associated with their implementation in electronic device applications are discussed.

Abstract

Molecular electronics that can produce functional electronic circuits using a single molecule or molecular ensemble remains an attractive research field because it not only represents an essential step toward realizing ultimate electronic device scaling but may also expand our understanding of the intrinsic quantum transports at the molecular level. Recently, in order to overcome the difficulties inherent in the conventional approach to studying molecular electronics and developing functional device applications, this field has attempted to diversify the electrical characteristics and device architectures using various types of heterogeneous structures in molecular junctions. This review summarizes recent efforts devoted to functional devices with molecular heterostructures. Diverse molecules and materials can be combined and incorporated in such two- and three-terminal heterojunction structures, to achieve desirable electronic functionalities. The heterojunction structures, charge transport mechanisms, and possible strategies for implementing electronic functions using various hetero unit materials are presented sequentially. In addition, the applicability and merits of molecular heterojunction structures, as well as the anticipated challenges associated with their implementation in device applications are discussed and summarized. This review will contribute to a deeper understanding of charge transport through molecular heterojunction, and it may pave the way toward desirable electronic functionalities in molecular electronics applications.

High-resolution multicolor patterning is achieved in a hybrid perovskite nanosheet, of which the linewidth can be down to ≈150 nm. A single perovskite nanosheet can not only gradually alter the color of the same pattern in a wide wavelength range, but also display different colors simultaneously. A perovskite photodetector with short channel length exhibits high responsivity.

Abstract

Ultrathin hybrid perovskites, with exotic properties and two-dimensional geometry, exhibit great potential in nanoscale optical and optoelectronic devices. However, it is still challenging for them to be compatible with high-resolution patterning technology toward miniaturization and integration applications, as they can be readily damaged by the organic solvents used in standard lithography processes. Here, a flexible three-step method is developed to make high-resolution multicolor patterning on hybrid perovskite, particularly achieved on a single nanosheet. The process includes first synthesis of precursor PbI₂, then e-beam lithography and final conversion to target perovskite. The patterns with linewidth around 150 nm can be achieved, which can be applied in miniature optoelectronic devices and high-resolution displays. As an example, the channel length of perovskite photodetectors can be down to 126 nm. Through deterministic vapor-phase anion exchange, a perovskite nanosheet can not only gradually alter the color of the same pattern in a wide wavelength range, but also display different colors simultaneously. The authors are optimistic that the method can be applied for unlimited perovskite types and device configurations for their high-integrated miniature applications.

A synergistic use of finite element simulations as a guide together with tellurization process by chemical vapor deposition allows to evidence the key role of tilt angle and distribution of Te vapor concentration gradient at the substrate position in the reactor to obtain molybdenum ditelluride few-layer nanosheets on large area growth and phase selectivity, namely pure 1T’ or 2H phase.

Abstract

Among transition metal dichalcogenides, molybdenum ditelluride (MoTe₂) holds significant attention due to its polymorphic nature including semiconducting, metallic, and topological semimetal phases. Considerable efforts are devoted to synthesizing MoTe₂ nanosheets to make them suitable for device integration in nanotechnologies and for fundamental investigations. In this respect, chemical vapor deposition (CVD) via tellurization of a pre-deposited Mo thin film is an easy and flexible way for synthesizing large scale MoTe₂ nanosheets. Here, the study report on the CVD of large-area (up to 4 cm × 1 cm) MoTe₂ nanosheets with pure 1T’ and 2H phase selection by design. Within the tellurization scheme, the vapor-solid reaction between the pre-deposited molybdenum film and tellurium vapor is studied thus optimizing the scalability and quality of the MoTe₂ nanosheets grown on SiO₂/Si substrates. It is demonstrated that the MoTe₂ structure and morphology are kinetically dictated by the tellurium concentration gradient on the reaction site with varying geometric configurations inside the CVD reactor. This study provides a pivot scheme for enabling scalable 1T’ and 2H-MoTe₂ integration in applications for novel micro- and nano-electronics, spintronics, photonics, and thermoelectric devices.

Ionogels are an emerging class of hybrid materials endowed with outstanding thermal, electrical, and mechanical properties. This material system's high versatility and superior tunability attract significant interest among researchers encompassing a broad spectrum of applications, including energy, flexible electronics, and biomedical. This review paper focuses on exploring the interactions within ionogels and their influence on electrochemical and mechanical performance.

Abstract

Ionogels have established themselves as an intriguing type of composites, owing to their distinctive properties, including superior thermal stability, non-flammability, tunable electrochemical stability window, and high ionic conductivity. Hybrid materials based on ionic liquids (ionogels) are held together by interfaces arising out of intermolecular interactions, including electrostatic, van der Waals, solvophobic, steric, and hydrogen bonding. The interfaces within the ionic liquid (ILs) and its multifaceted interplay with the encapsulating matrix greatly influence the physicochemical and electronic/ionic interactions within the composite resulting in exceptional characteristics, allowing for the design of ionogels for targeted applications. Though ionogels have shown superior properties comparable to neat ILs, they still exhibit relatively low mechanical strength, limiting their application in several practical technologies. Simultaneous enhancement of mechanical durability while retaining high ionic conductivity is indispensable, which requires understanding interfaces and related influencing parameters. This review provides a synergetic comprehension, focusing on the interactive forces and factors affecting the conductivity, stability, and robustness of ionogels. Correlating with interfaces, several strategies, including the implications of nanofiller incorporation on the electromechanical properties of ionogel, are also elaborated. Finally, a primer is provided on the application of ionogels in sensors and energy harvesting technologies.

npj 2D Materials and Applications, Published online: 23 October 2022; doi:10.1038/s41699-022-00346-0

An in situ crystallized Sb₂Te₃/GeTe superlattice film is grown by atomic layer deposition on the planar and sidewall memory cell, showing a significantly decreased reset current compared with the homogeneously mixed alloy. The in-plane compressive stress and effective electromigration of the Ge atoms induce a melt-quenching-free amorphization mechanism.

Abstract

Atomic layer deposition (ALD) of Sb₂Te₃/GeTe superlattice (SL) film on planar and vertical sidewall areas containing TiN metal and SiO₂ insulator is demonstrated. The peculiar chemical affinity of the ALD precursor to the substrate surface and the 2D nature of the Sb₂Te₃ enable the growth of an in situ crystallized SL film with a preferred orientation. The SL film shows a reduced reset current of ≈1/7 of the randomly oriented Ge₂Sb₂Te₅ alloy. The reset switching is induced by the transition from the SL to the (111)-oriented face-centered-cubic (FCC) Ge₂Sb₂Te₅ alloy and subsequent melt-quenching-free amorphization. The in-plane compressive stress, induced by the SL-to-FCC structural transition, enhances the electromigration of Ge along the [111] direction of FCC structure, which enables such a significant improvement. Set operation switches the amorphous to the (111)-oriented FCC structure.

Nature Communications, Published online: 23 October 2022; doi:10.1038/s41467-022-33822-8

Publication date: February 2023

Source: Progress in Materials Science, Volume 132

Author(s): Shucheng Xing, Jian Zhou, Xuanguang Zhang, Stephen Elliott, Zhimei Sun

Author(s): Junxi Duan, Yu Jian, Yang Gao, Huimin Peng, Jinrui Zhong, Qi Feng, Jinhai Mao, and Yugui Yao

In the second-order response regime, the Hall voltage can be nonzero without time-reversal symmetry breaking but inversion symmetry breaking. Multiple mechanisms contribute to the nonlinear Hall effect. The disorder-related contributions can enter the NLHE in the leading role, but experimental inves…

[Phys. Rev. Lett. 129, 186801] Published Mon Oct 24, 2022

Nature Nanotechnology, Published online: 24 October 2022; doi:10.1038/s41565-022-01222-0

Nature Photonics, Published online: 24 October 2022; doi:10.1038/s41566-022-01084-x

The covalent modification of graphene supported on a surface makes it possible to control the graphene reactivity, tailor its electronic properties, and immobilize active molecules. Based on a critical comparison of the different chemical routes, this Review provides up-to-date guidelines for working with chemically modified 2D materials on a surface.

Abstract

In the last decade, the use of graphene supported on solid surfaces has broadened its scope and applications, and graphene has acquire a promising role as a major component of high-performance electronic devices. In this context, the chemical modification of graphene has become essential. In particular, covalent modification offers key benefits, including controllability, stability, and the facility to be integrated into manufacturing operations. In this Review, we critically comment on the latest advances in the covalent modification of supported graphene on substrates. We analyze the different chemical modifications with special attention to radical reactions. In this context, we review the latest achievements in reactivity control, tailoring electronic properties, and introducing active functionalities. Finally, we extended our analysis to other emerging 2D materials supported on surfaces, such as transition metal dichalcogenides, transition metal oxides, and elemental analogs of graphene.

Nature Materials, Published online: 25 October 2022; doi:10.1038/s41563-022-01378-z

Nature Materials, Published online: 25 October 2022; doi:10.1038/s41563-022-01383-2