Technology-based industries are constantly seeking materials and methods to fabricate compact, high-performance, and increasingly more complex printed electronic devices, fostering research in advanced conductive inks and processing techniques. Metal–organic decomposition (MOD) inks are a class of conductive inks based on molecular metal precursors that decompose into metallic features once printed, imparting them with unique attributes that distinguish them from particle-based inks. This Spotlight on Applications summarizes recent progress in understanding the chemistry, rheology, and printability of MOD inks that enable them to be printed, processed, and used with material substrates in unconventional ways. Their unique properties and capabilities are being leveraged to advance the field of printed electronics, from their use in 2.5D and 3D surfaces, wearables, and fine line printing and thus broadening the form factors and improving properties of devices used in the medial, automotive and aerospace industries.

In the world of consumer electronics, flexible and wearable electronic devices have witnessed a remarkable transformation, and flexible supercapacitors (SCs) hold tremendous potential as a power source for these electronic devices. Printing technologies, such as inkjet and screen printing, have emerged as cost-effective and scalable manufacturing techniques for the fabrication of flexible SC electrodes. As a key element of printing technology, ink must have the right balance of conductivity and rheological properties to fabricate high-performance flexible electrodes. Graphene stands out as a promising active pigment for conductive ink due to its remarkable characteristics such as high surface area, excellent electrical conductivity, and mechanical properties. Recently, extensive research has been conducted on the development of graphene-based inks for their effective utilization in SC printing methods. This review summarizes these advances and systematically connects the graphene ink formulation with its rheological properties and correlates finally with the electrochemical performance of inkjet- and screen-printed SC electrodes.

To meet future demands for sustainable and environmentally friendly technology, many research groups are focusing on triboelectric nanogenerators (TENGs), which can scavenge and convert the available mechanical energy into electrical energy. Researchers are working to comprehend the influence of triboelectric material surfaces as well as the properties that play an important role in determining the overall output performance of TENGs. The selection of tribonegative and tribopositive materials based on the charge in triboseries and different processes for manufacturing the triboactive material and its surface modification play important roles in attaining optimal TENG performance. The most significant tribonegative material is polyvinylidene fluoride (PVDF), and its electroactive polar β-crystalline phase is responsible for higher TENG performance. However, PVDF has some intrinsic limitations such as lower electrical conductivity and dipole moment and nonpolar α-crystalline phase at room temperature. Interestingly, these are the main factors that determine the output performance of TENG applications in energy harvesting and wearable sensors. In this review, we have mainly focused on the influence of varying processing methods like solution casting, 3-D printing, spin coating, and electrospinning on the output performance of PVDF-based TENGs. The effect of nanoscale materials on the PVDF crystalline phase is also studied in detail. Additionally, an extensive analysis of recent advancements in health monitoring, wearable sensors, and energy harvesting applications of PVDF-based TENGs is included.

Due to the fast evolution of information technology, high-speed and scalable memory devices are being investigated for data storage and data-driven computation. Resistive switching random access memory (RRAM) is one of the very popular types of memristors, because of its quick program/erase speed and high density as a result of its simple two-terminal structure, low power consumption, and low cost of fabrication. In this review, the market for promising memristor-based memories for smart systems is examined. The switching memory devices are described and classified according to their I–V behavior to underline the physical switching mechanisms. The various filament mechanisms of the RRAM memristor, including the valence change mechanism (VCM), electrochemical metallization mechanism (ECM), and thermochemical mechanism (TCM), are especially highlighted in various structures. The performance of resistive switching devices with different reported electrode materials and resistive layers is summarized. This study provides a detailed review of materials of the different deposition techniques used for surface modification and coating. The two major areas of interest, physical and chemical vapor deposition techniques and the influence parameter on the resistive switching, are discussed in detail. The prospective applications of RRAM memristors to various fields such as security, neuromorphic computing, and non-volatile logic systems for artificial intelligence are addressed briefly as well as the future outlook.

To tackle the deteriorating electromagnetic interference and pollution problems, enhanced microwave absorption materials are urgently being developed. Low-dimensional molybdenum disulfide (MoS2) nanostructures have been comprehensively researched and employed as microwave absorption materials in virtue of their tailorable valence bands, ample active polarization sites, appropriate electronic band configuration, ample morphologies, distinctive dielectric, and electric behaviors. The excellent merits are expected to satisfy the extensive and unique application requirements. Low-dimensional MoS2 nanostructure microwave absorption materials excel in ultrathin thickness, lightweight, broad effective absorption bandwidth, and strong attenuation capability. The advantages are due to well-matched impedance matching, multiple polarization relaxations, and multiple reflections and scatterings effect. This review sketches up the theories on microwave propagation, attenuation, and performance evaluation. Simultaneously, the preparation methods of low-dimensional MoS2 nanostructures are elaborately categorized. More importantly, the cutting-edge research progresses on low-dimensional MoS2 nanostructures for microwave absorption are thoroughly combed. Finally, some perspectives and challenges for the future orientation of low-dimensional MoS2 nanostructures are highlighted. Without doubt, low-dimensional MoS2 nanostructures have illuminated boundless roadmaps for further advancement as high-performance microwave absorption materials.

In order to attain high-performance p-type field-effect transistors (FETs) based on two-dimensional materials, it becomes imperative to mitigate Fermi level pinning. Employing Bi with a low work function of ∼4.2 eV, characterized by its low melting point, significant vapor pressure, and smaller density of states, has been instrumental in establishing pinning-free n-type contacts. In this context, we present a new approach for establishing p-type contacts. This approach involves the modulation of the effective work function through a bilayer electrode structure comprising ultrathin Bi and a thick Au with a high work function of ∼5.1 eV. The modulation of the effective work function has been clearly confirmed through capacitance─voltage measurements, conducted as a function of the thickness of the Bi layer. Consequent to these findings, a p-type WSe2 Schottky FET was demonstrated employing 2-nm-thick Bi/Au electrodes.

We investigated the impact of predeposition surface treatment with a tetramethylammonium hydroxide (TMAH) solution on the performance of recessed gate metal–insulator–semiconductor-high-electron-mobility transistors (MIS-HEMTs). When applying the forward step stress, gate leakage current of the TMAH-treated device becomes 1 order of magnitude smaller. Step stress tests carried out at various voltages showed a stable threshold voltage with both the reverse gate bias step stress and the off-state drain step stress contributing to the high-quality Al2O3/AlGaN interfaces. When the temperature was increased to 473 K, the maximum field effective mobility (μFE) was improved from 450 to 483 cm2/V·s, and on-resistance was improved by ∼6.8%.

Nonlinearities play a critical role in the dynamics of mechanical resonators, enhancing sensitivity and enabling signal manipulation. Understanding the parameters affecting nonlinearities is crucial for developing strategies to counteract their effects or manipulate them for improved device performance. This study investigates the impact of fabrication-induced curvature on the dynamics of zinc-oxide-based piezoelectric micromachined ultrasonic transducers (PMUTs). Our experiments reveal that these devices exhibit hardening, softening, and mixed nonlinear responses with varying initial static displacements. Notably, PMUTs with an almost flat initial static displacement exhibit hardening nonlinearity, while those with a curved initial static displacement show softening nonlinearity. An exotic mixed nonlinear response is observed for intermediate static displacement. We attribute the observed nonlinear response to the interplay between static displacement induced quadratic nonlinearity and midplane-stretching induced cubic nonlinearity. We provide a theoretical formulation for the dynamics of the devices, which explains the experimental results and highlights the nonlinear responses and their dependence on the initial static displacement. Our findings underscore the significance of nonlinearities in the dynamics of mechanical resonators and suggest ways to optimize the device performance.

In this study, the effects of vacancy defects and substitutional doping on the structural, electronic, and linear optical characteristics of the magnesium dichloride (MgCl2) monolayer are investigated using density functional theory. The GGA-PBE functional is used to derive optical characteristics such as real and imaginary parts of the dielectric function, absorption coefficient, extinction coefficient, refractive index, reflectivity, and electron energy loss function. The results reveal that creating a Cl atom vacancy inside the MgCl2 monolayer is energetically favorable, and the study provides insights into how vacancy defects and substitutional doping can be utilized to modulate the electronic and optical properties of the MgCl2 monolayer for potential applications in optoelectronics. The outcomes of this research can potentially lead to the growth of more efficient and effective optoelectronic devices.

Two-dimensional (2D) quantum spin Hall (QSH) insulators have attracted a great deal of attention since they enable the dissipationless transport of electrons, which serve as ideal candidates for designing miniaturized electronic devices. Here, through first-principles calculations, the Sn2BN monolayer is proved as a 2D material with excellent thermodynamic stability that can realize the QSH effect under the action of biaxial strain. Such a nontrivial topology is characterized through the band inversion related to Sn-px,y with B-pz orbitals at the Γ point induced by spin–orbit coupling (SOC) and confirmed by the Z2 invariant and gapless helical edge states. More interestingly, by employing specific tensile strain, the Sn2BN monolayer can host the characteristic of a negative Poisson’s ratio. In addition to biaxial strain, the external electric field is also an effective technique to tune the global band gap of the Sn2BN monolayer. Our findings reveal the strain-induced outstanding topological and mechanical properties in the Sn2BN monolayer, which provide a platform for designing multifunctional quantum devices.