Materials Today Electronics最新文献

Intrinsic magnetic two-dimensional (2D) materials with high critical temperature are highly desired in advanced spintronics applications. Via first-principles calculations, we firstly predict that two-dimensional molybdenum carbide (with a chemical formula of Mo${}_2$C₁₂) monolayer is a highly stable antiferromagnetic (AFM) semiconductor with a band gap around 1 eV and a high Néel temperature of 420 K. We then show that the multilayer (Mo${}_2$C₁₂)${}_n$, where $n$ is the number of layers, exhibits interesting electronic and magnetic properties that are sensitively dependent on the number of layers. The stability of the AFM configuration and the energy gap rapidly decrease with the number of layers. When $n\le 5$, (Mo${}_2$C₁₂)${}_n$ remains AFM, while magnetic moments are mainly located on surface Mo atoms, and Mo atoms on top and bottom surfaces have opposite spin polarizations. When $n>5$, the AFM phase is unstable and the material becomes metallic. These layer-tunable properties make (Mo${}_2$C₁₂)${}_n$ potentially useful for various electronics and spintronics applications. As one example, an intriguing (Mo${}_2$C₁₂)${}_5$ based magnetic metal–semiconductor–metal heterojunction is proposed in this work.

Recent experiments evidence the direct observation of spin waves in chromium trihalides and the presence of a gap at the Dirac points of the magnon dispersion in bulk CrI${}_3$. However, the topological origin of this feature remains unclear and its emergence at the 2D limit has not yet been proven experimentally. Herein, we perform a fully self-consistent ab initio analysis to deeply understand magnetic exchange of chromium trihalides in the 2D limit. We compute the orbital dependent magnetic interactions and Curie temperatures under applied biaxial strain. Our results confirm the existence of a gap around the K high-symmetry point in the linear magnon dispersion of CrI${}_3$, which originates as a direct consequence of intralayer Dzyaloshinskii–Moriya (DM) interaction. In addition, our orbital resolved analysis reveals the microscopic mechanisms that can be exploited using strain engineering to increase the strength of the DM interaction and thus control the topological gap width in CrI${}_3$. This paves the way to the further development of this family of materials as building-blocks for topological magnonics at the limit of miniaturization.

There is no wonder that flexible electronics can be considered as a boon for mankind because of its inherent characteristics of portability, stretchability, bendability, and wearability which makes it an ideal vehicle for a plethora of biomedical applications. Flexible electronic device, often integrated for wearable electronics and energy storage electrochromic device, (ESED) is a snowballed research area. This review focuses on the development of flexible ESED where charging and discharging of energy storage device is coupled with decoloration and coloration of an electrochromic device. The strategy behind the integration of energy storage and electrochromic device as a bi-functional device is discussed in length. The essential key parameters for fabrication of flexible ESED and the performance parameters of the flexible ESED have been highlighted. A quantitative analysis of flexible ESED fabricated using different materials has been presented while dwelling into details of possible materials candidates and challenges encountered so far with a possible direction of future research. Enveloping the major research developments in the field of flexible ESED while addressing the possible challenges, a future outlook in the mentioned research thrust have been presented.

Vision is our dominant sense and is also highly desired in artificial systems. In this article, we provide an overview of bio-inspired visual systems that utilize curved image sensors and/or photonic synapses. The use of curved detector geometry ensures clear image sensing abilities with fewer optical elements, which has the potential to lead to miniaturization. Additionally, photonic synapses that integrate light sensing and neuromorphic preprocessing can reduce redundant modules and signal communications. This results in decreased device size and energy consumption. In this review, we begin by summarizing the fabrication processes of curved image sensors, followed by a review of typical bionic eye systems. Next, we discuss the materials and device structures of typical photonic synapses and related imaging systems. We also review the combinations of curved image sensors and photonic synapses. Finally, we summarize the key advantages and challenges of current bio-inspired visual systems.

Due to their strong covalent binding interaction between adjacent layers, it was difficult to exfoliate non-layered materials compared to layered materials. Recently, Balan, et al. (Nat. Nanotechnol. 13, 602–609, 2018) prepared a non-van der Waals (non-vdW) two-dimensional (2D) hematene from hematite (α-Fe₂O₃) by liquid exfoliation. Subsequently, various approaches including chemical vapor deposition (CVD), molecular beam epitaxy (MBE), ion layer epitaxy (ILE), pulsed laser deposition (PLD), and polymer assisted deposition (PAD) have been developed. Notably, a general thermodynamics-triggered competitive growth (TTCG) model was proposed to design a new hydrate-assisted CVD (HACVD) of the 2D non-layered materials growth. Although existing methods have achieved some good results, there are still many obstacles to overcome. In this review, we aim to give an overview on the recent advances and challenges in synthesis of 2D non-vdW ferromagnetic materials, and future prospects of 2D non-layered materials.

This perspective explores the emerging field of spintronics within the context of two-dimensional van der Waals (vdW) heterostructures. Spintronics has opened exciting possibilities in the realm of two-dimensional (2D) materials. The integration of diverse 2D materials within vdW heterostructures has unveiled a plethora of previously unknown physical phenomena and potential applications related to spin-dependent transport, gate-tunable spin transport, spin filtering effects, and the emergence of ferromagnetism. These advancements have expanded the scope of spintronics beyond traditional bulk materials, offering unique opportunities for efficient spin injection, manipulation, and detection in 2D devices. A deep understanding of how different materials and interfaces are interconnected and how they affect spin properties is essential for improving the effectiveness and control of spin injection and detection. The study of spintronics in vdW heterostructures holds great promise for advancing the frontiers of developing the next generation of spintronic and quantum devices, revolutionizing information technology and nanoelectronics.

The liquid crystal photoalignment technique is a non-contact approach to establishing liquid crystal alignment using light irradiation, with the advantages of being non-polluting and non-electrostatic, and allowing facile microdomain orientation, compared with the rubbing alignment method. This review covers three categories of photoalignment under polarized light irradiation: photoisomerization, photodegradation, and photo-crosslinking. Photosensitive materials, such as azobenzene, polyimide, and cinnamate, are also introduced. Nonpolarized photoalignment technique is also presented. This review also summarizes the methods of controlling pretilt angle and increasing photosensitivity and several applications of the photoalignment technique. The photoalignment technique has considerable promise and value for liquid crystal displays, spatial filters, and flexible/stretchable devices.

The spin properties in van der Waals (vdW) low-dimensional materials have attracted increasing research interest due to their potential application in future nano-spintronic devices. Among the vast members of vdW materials, those with star-of-David (SOD) charge density wave (CDW) patterns are emergent. Here, we give a review of the recent experimental and theoretical progress achieved on this kind of material. First, the features and advantages of exploring spin properties in SOD materials are briefly introduced. Second, the influences of different stacking on the spin properties of SOD systems are discussed, from single-layer to bilayer and then to bulk with different phase combinations by taking advantage of the vdW nature, manifesting various spin phenomena such as the 120° in-plane antiferromagnetism, quantum spin liquid, and the Kondo effect. Then we give some examples of manipulation methods such as doping, strain, and electric field, which can induce the change of spin features. Finally, the current challenges and opportunities at the frontier in this research field are discussed.

We report on a magnetic domain wall (DW)-based spin torque nano-oscillator (STNO) with real-time multimodal frequency modulation characteristics by engineering the synergistic effect of shape anisotropy, Dzyaloshinskii-Moriya interaction (DMI), and spin-transfer torque. The achieved manageable oscillation and precession of magnetic DW motivate us to implement such attributes into the developed STNO under a low current density of ∼10⁷ A/cm², which demonstrates outstanding functionality of multimodal real-time modulation ranging from few GHz and sub-THz with corresponding few tens and >10⁴ quality factor (f_STNO/Δf ) in absence of external magnetic field. Furthermore, the dynamic process of DW motion and magnetic moment precession under different modes has been revealed systematically, and the frequency dependence of various physical parameters including damping constant, uniaxial anisotropy constant, saturation magnetization, exchange stiffness, and DMI constant has also been summarized in detail. Such a DW-based device enriches the STNO family and promises great potential with a broad spectrum of applications in microwave generators and neuromorphic computing.

The implementation of resistive switches in neuromorphic computing and long-term data storage has been delayed by inherent difficulties in their fabrication process, their stability and reproducibility. Low operating voltages, high-density integration and low energy consumption are common challenges in resistive switch design. Here, we report the implementation of a resistive switch based on the amorphous semiconductor Ge${}_{15}$As${}_{25}$Se${}_{15}$Te${}_{45}$ (GAST) between an inert (W) and an active (Ag) electrode. The device was built using contact photolithography and standard microfabrication techniques, allowing the integration with traditional manufacturing processes. The device is able to switch at voltages as low as 0.15 V and 0.6 V, when operating in DC and pulsed conditions, respectively. Our results suggest that the adoption of mixed conductors such as GAST may yield devices that operate at low voltages and low energy for neuromorphic applications.