Nanoelectronic Devices Research Articles

Enormous Out-of-Plane Charge Rectification and Conductance through Two-Dimensional Monolayers.

Heterogeneous integration of emerging two-dimensional (2D) materials with mature three-dimensional (3D) silicon-based semiconductor technology presents a promising approach for the future development of energy-efficient, function-rich nanoelectronic devices. In this study, we designed a mixed-dimensional junction structure in which a 2D monolayer (e.g., graphene, MoS2, and h-BN) is sandwiched between a metal (e.g., Ti, Au, and Pd) and a 3D semiconductor (e.g., p-Si) to investigate charge transport properties exclusively in an out-of-plane (OoP) direction. The role of 2D monolayers as either an OoP metal-to-semiconductor charge injection barrier or an OoP semiconductor-to-metal charge collection barrier was comparatively evaluated. Compared to monolayer graphene, monolayer MoS2 and h-BN effectively modulate OoP metal-to-semiconductor charge injection through a barrier tunneling effect. Their effective OoP resistance and resistivity were extracted using a resistors-in-series model. Intriguingly, when functioning as a semiconductor-to-metal charge collection barrier, all 2D monolayers become electronically "transparent" (close to zero resistance) when a high OoP voltage (greater than the built-in voltage) is applied. As a mixed-dimensional integrated diode, the Ti/MoS2/p-Si and Au/MoS2/p-Si configurations exhibit both high OoP rectification ratios (5.4 × 104) and conductance (1.3 × 105 S/m2). Our work demonstrates the tunable OoP charge transport characteristics at a 2D/3D interface, suggesting the opportunity for 2D/3D heterogeneous integration, even with sub-1 nm thick 2D monolayers, to enhance modern Si-based electronic devices.

Design a novel PVA embedded Ag@CdS Core@Shell nano-crystals for potential nanoelectronic devices

The approach emphasizes dispersing Ag@CdS (ACS) core@shell (CS) nanocrystals (NCs) in polyvinyl alcohol (PVA) and activating them at room temperature via a straightforward wet chemical co-precipitation process. The improved performance of ACS NCs is due to their CS shape, surface plasmon resonance (SPR), and quantum confinement phenomena. The UV-Vis and PL spectroscopy revealed variations in optical properties, including a tunable band gap in CdS quantum dots, indicating their potential as nanoelectronic (NE) devices. The XRD, TEM, and SEM measurements validated the nanoscale development of ACS NCs on the PVA surface. Findings NCs have excellent dielectric characteristics in capacitors, which improves energy storage efficiency as capacitance falls with frequency due to increased polarization. The assemblies outperform those with simply core or shell NCs, with ACS CS NCs producing a peak dielectric constant of 106, capacitance of 200 nF, conductivity of 0.1, and a voltage gain of 91% at specific frequencies. The incorporation of ACS NCs into PVA has major implications for future NE applications, including low-pass frequency filters, energy conversion, energy storage, memristive devices, and sensors. This study enhances energy-efficient technologies by embedding ACS in a stable PVA matrix, improving nanocrystals' functionality and stability for NEs devices.

Size effect on Raman measured stress and strain induced phonon shifts in ultra-thin silicon film

The fabrication of complex nano-scale structures, which is a crucial step in the scaling of (nano)electronic devices, often leads to residual stress in the different layers present. This stress gradient can change many of the material properties, leading to changes in device performance, especially in the active part of the transistor, the channel. Measuring, understanding, and, ultimately, controlling the stress fields is hence crucial for many design steps. The level of stress can in principle be measured by micro-Raman spectroscopy. This, however, requires a priori knowledge of the mechanical properties of the material. However, mechanical properties start to deviate from the bulk values when film dimensions become thinner than 5 nm. If this effect is ignored, errors of up to 400% can be introduced in the extracted stress profile. In this work, we illustrate this effect for a range of Si (001) slabs with different silicon film thicknesses, ranging from 5 to 0.7 nm and provide best practices for the proper interpretation of micro-Raman stress measurements.

Raman activity and high electron mobility of piezoelectric semiconductor GaSiX2 (X = N, P, and As) toward flexible nanoelectronic devices

Abstract Inspired by the urgent demand for novel multifunctional materials in advanced technology applications, herein, first-principles calculations are utilized to construct new two-dimensional GaSiX 2 (X = N, P, As) monolayers. After optimizing the GaSiX 2 crystal structures, their stabilities, Raman responses, piezoelectricity, and electronic/transport characteristics are systematically studied. Results from phonon dispersions, ab initio molecular dynamics simulations, elastic constants, and cohesive energies confirm the good dynamic, thermal, energetic, and mechanical stabilities of the proposed GaSiX 2 monolayers. Based on the Heyd–Scuseria–Ernzerhof approach, the GaSiX 2 exhibit semiconductor behaviors with favorable bandgaps for absorption of the visible spectrum of 1.82 for GaSiP2 and 1.43 eV for GaSiAs2 monolayer. In addition, the GaSiX 2 monolayers also show piezoelectric effects, and high in-plane piezoelectric coefficients d 11 are found for the GaSiP2 (−1.16 pm V − 1 ) and GaSiAs2 (−1.26 pm V − 1 ). The carrier mobilities of the GaSiX 2 are estimated by the deformation potential method for their transport properties. Along two in-plane transport directions, the carrier mobilities of the GaSiX 2 are anisotropy for holes and electrons. GaSiP2 and GaSiAs2 show large electron mobilities along the x axis of 2816.99 and 1211.41 cm2V−1s−1, respectively. Thus, the GaSiP2 and GaSiAs2 monolayers not only have high anisotropic electron mobilities but also favorable bandgaps and large piezoelectric coefficients, indicating potential applications of GaSiP2 and GaSiAs2 in electronic, photovoltaic, and piezoelectric devices. The findings of this study may provide insights into the GaSiX 2 monolayers for multifunctional applications.

Two-Dimensional Ferroelectric Materials: From Prediction to Applications

Ferroelectric materials hold immense potential for diverse applications in sensors, actuators, memory storage, and microelectronics. The discovery of two-dimensional (2D) ferroelectrics, particularly ultrathin compounds with stable crystal structure and room-temperature ferroelectricity, has led to significant advancements in the field. However, challenges such as depolarization effects, low Curie temperature, and high energy barriers for polarization reversal remain in the development of 2D ferroelectrics with high performance. In this review, recent progress in the discovery and design of 2D ferroelectric materials is discussed, focusing on their properties, underlying mechanisms, and applications. Based on the work discussed in this review, we look ahead to theoretical prediction for 2D ferroelectric materials and their potential applications, such as the application in nonlinear optics. The progress in theoretical and experimental research could lead to the discovery and design of next-generation nanoelectronic and optoelectronic devices, facilitating the applications of 2D ferroelectric materials in emerging advanced technologies.

Multifunctional Native Defects Boosting the Thermoelectric Transport in Few‐Layer PdPS

AbstractAs a unique Cairo pentagonal 2D material, palladium phosphide sulfide (PdPS) has garnered immense interests due to its excellent optoelectronic properties, anisotropic electronic transport behavior, and good air‐stability. In addition, its puckered pentagon structure renders an ultralow thermal conductivity, making it a promising candidate for thermoelectrics applications. However, its thermoelectric transport has not been studied until now due to challenges in obtaining the atomic thin PdPS flake and further measurement. In this work, the thermoelectric performance of 2D PdPS is investigated. It is found that thermoelectric property of PdPS can be effectively manipulated via the delicate annealing treatment, which effectively regulate the defect concentrations. Remarkably, beyond regulating carrier concentrations and shifting the Fermi level closer to the conduction band, these defects also produce a large number of defect states. Consequently, ultra‐high power factor of 0.648 mW m−1 K−2 at room temperature is achieved, outperfoming other 2D materials reported to date. Furthermore, the anisotropic electronic transport properties of few‐layer PdPS are further studied and an extremely high electron anisotropic ratio of 47.37 are obtained at 20 K. The findings provide a new pathway for the development of nanoelectronic devices based on emerging 2D materials with high electronic anisotropy and thermoelectric performance.

Constructing conical helices inside carbon nanocones.

Molecular dynamics simulations demonstrate that regular conical helices of poly(para-phenylene) (PPP) chains can be constructed inside the confined space of single-walled carbon nanocones (CNCs). The translocation displacement of the PPP chain combined with the change of the system total potential energy including each energy component and structural parameters of the formed conical helix is discussed to deeply explore the microstructure evolution, driving forces and dynamic mechanisms. In addition, the influence of chain length, cone angle, temperature, chain number, linked position of benzene rings and the form of Lennard-Jones potential on the helical encapsulation is further studied. The proposed method may provide a new way for constructing regular conical helices from polymer chains, with potential applications in electronic nanodevices.

Molecular dynamics simulation of bending behavior of B2-FeAl alloy nanowires with different crystallographic orientations

In nanosystems, the metallic nanowires are subjected to significant and cyclic bending deformation upon integration into stretchable and flexible nanoelectronic devices. The reliability and service life of these nanodevices depend fundamentally on the bending mechanical properties of the metallic nanowires that serve as the critical components. A deep understanding of the deformation behavior of the metallic nanowires under bending is not only essential but also imperative for design and manufacture of high-performance nanodevices. To explore the mechanism underlying the bending plasticity of the metallic nanowire, we have conducted a study on the bending deformation of B2-FeAl alloy nanowires with various crystallographic orientations, sizes and cross-sectional shapes by using molecular dynamics simulation. Our results show that the bending behavior of the B2-FeAl alloy nanowires is independent of the size and cross-sectional shape of the nanowire, but it is highly sensitive to its axial orientation. Specifically, both <111>- and <110>-oriented nanowires yield by dislocation nucleation upon bending, in which the <111>-oriented nanowire fails by brittle fracture soon after yielding, while the <110>-oriented nanowire exhibits good ductility due to homogeneous plastic flow raised by continuous nucleation and steady motion of dislocations. In contrast to the aforementioned two nanowires, the bending plasticity of the <001>-oriented nanowire is mediated by stress-induced transformation from B2 to L1<sub>0</sub> phases, which leads to excellent ductility and higher fracture strain. The orientation dependence of bending deformation can be understood by considering the Schmid factor. Moreover, the plastically bent nanowires with <110> and <001> orientations are able to recover to their original shape upon unloading, particularly, the plastic deformation in the <001>-oriented nanowire is recoverable completely via reverse transformation from L1<sub>0</sub> to B2 structures, exhibiting superelasticity. This work elucidates the deformation mechanism of the B2-FeAl alloy nanowire subjected to bending load, which provides a crucial insight for the design and optimization of flexible and stretchable nanodevices based on metallic nanowires.

Quantitative Study of Reversible Nonvolatile VO2 Thin Films Through Plasma Driven Phase Engineering Process

AbstractThe nanoscale control of phase transition in correlated materials offers significant insight into phase transition dynamics for the advancement of future nanoelectronics devices. This study explores the phase transition phenomenon in vanadium dioxide (VO2), focusing on the heterogeneous phases evolved after low‐pressure plasma irradiation on VO2 thin films, a strong electron‐correlated material. The modulation in the Argon (Ar) plasma power reveals the formation of homogeneous and heterogeneous phases with variable resistive states at room temperature. High‐resolution transmission electron microscopy (HRTEM) is observed with the change in interplanar spacing revealing monoclinic (M1) at 0W, monoclinic‐tetragonal rutile (phase coexistence, M1‐R) at 50W, and tetragonal rutile (R) at 90W. Dielectric force microscopy (DFM) shows distinct dielectric responses corresponding to different phases, characterized by potential differences of 3 mV (M1), 5 mV (M1‐R), and 7.44 mV (R) phases. The coexistence of M1‐R phase is stabilized and examined at room temperature, with variations in the charge carrier density observed relative to M1 and R phases individually. The phase change in VO2 is found to be reversible, enabling stable resistive states even after the plasma is removed. The changes in plasma geometry help find and stabilize unstable phases, which can be useful in nanoelectronics.

An insight into the influence of CuO NPs on the structural, dielectric, optical, and conductivity properties of PEO/PVA-CuO nanocomposite for energy storage nanoelectronic devices

An insight into the influence of CuO NPs on the structural, dielectric, optical, and conductivity properties of PEO/PVA-CuO nanocomposite for energy storage nanoelectronic devices

Engineering the band structure of type-II MoSe2/WSe2 van der Waals heterostructure by electric field and twist angle: a first principles perspective

Type-II heterostructures composed of transition-metal dichalcogenides have attracted enormous attention due to their facilitation in efficient electron-hole separation. In this work, we performed density-functional theory calculations to systematically investigate the atomic and electronic structures of MoSe2/WSe2van der Waals heterostructure. Its six high-symmetry configurations with different interlayer coupling under external electric field and twist angle were addressed. Our results reveal that all the configurations exhibit type-II band alignment and their band gaps can be effectively modulated by the electric field. Notably, the direct to indirect band gap transition only occurs in the configurations with strong interlayer coupling. Moreover, twist-induced symmetry breaking weakens the interlayer interactions, thus decreasing interlayer charge transfer. Owing to large interlayer distance and weak interlayer coupling, the band structure of the heterostructure remained unchanged for the twist angles ranging from 13.2° to 46.8°. These findings demonstrate the great potential of the MoSe2/WSe2heterostructure for applications in optoelectronic and nanoelectronic devices.

Electronic, magnetic, and topological properties of ferromagnetic 2D perovskite-type oxides

Abstract Two-dimensional (2D) materials within the hematene-type binary oxides and perovskites family have recently gathered huge research interest for nanoelectronic devices. However, the exploration of their fascinating topological properties remains limited. Herein, through first-principles calculations, we systematically examine the electronic, magnetic, and topological properties of substitutionally doped 2D ABO3 (A=As, Sb, or Bi, and B = V, Nb, or Ta) perovskite structures at the B site of a B2O3 system. Interestingly, the atomic substitution makes the 2D ABO3 structures dynamically stable. Our detailed calculations show the ferromagnetic and antiferromagnetic phases of these materials. The calculated Chern number (C) for the ferromagnetic 2D ABO3 (A = As, Sb, or Bi, B = Nb or Ta) suggests their topologically non-trivial phases. Furthermore, the computed nontrivial Berry curvature highlights the topological properties in AsNbO3. These findings highlight opportunities in 2D-ABO3 materials, for applications in spintronics.

Ferroelectric Domains Engineering in 2D Van Der Waals Ferroelectric α‑In2Se3 Via Flexoelectric Effect.

2D) Van der Waals ferroelectrics offer the opportunity for developing novel nanoelectronics devices. For device applications, it is necessary to generate controllable ferroelectric polarization domains and achieve non-destructive polarization switching. However, it is very challenging to use the electric field to manipulate the domain state of ultra-thin ferroelectric film due to the large leakage current and even electric breakdown. Here, the flexoelectric effect on the manipulation of polarization states at bending α-In2Se3 flakes is explored via piezoresponse force microscopy (PFM). By introducing patterned Si trench substrates, the stripe micron-scale ferroelectric domains with alternating arrangements of the out of-plane polarization in the curved α-In2Se3 are observed. It is found that the polarization at the bending region of α-In2Se3 can be directly reversed by the large flexoelectric field. The controllable mechanical modulation of α-In2Se3 ferroelectric domains opens up potential applications of ferroelectrics in strain engineering functional devices.

Dynamics of Ferroelectric Flux Closure Array in Oxide Superlattices.

Topological polar soliton such as skyrmions, merons, vortices, flux closures represent topologically nontrivial structures with their stability governed by specific boundary conditions. These polar solitons can be utilized in enhancing memory density and reducing energy consumption in nanoelectronic devices. Flux closure domains exhibit high density and thermal stability, with a strain gradient as large as ≈106m-1 at the core, which is tunable by adjusting the materials thickness, periodicity. The practical utilization of topological structures like flux closure in advanced applications requires the ability to manipulate them using external stimuli and ensuring their stability under thermal excitation. In this study, piezo-force microscopy is employed to investigate the manipulation of flux closure nano-domains through external electric field and temperature to observe their evolution. The findings demonstrate that the application of electric field can create or annihilate these nano-domains and modify their density. Temperature variations significantly affect the density of flux closure domains, domain walls, correlating with enhanced capacitance of the system. This is crucial for improving the memory density of storage devices. Thus, by adjusting the density of these domains, it is possible to tailor the functional properties of nanoelectronic devices, such as capacitance and electromechanical response, enabling advanced application.

Review of: "The application of graphene nano-ribbons in nano-interfering electromagnetic shielding materials and nano-electrostatic discharge in nano-electronic devices"

Review of: "The application of graphene nano-ribbons in nano-interfering electromagnetic shielding materials and nano-electrostatic discharge in nano-electronic devices"

Layer-dependent electronic and magnetic properties of SrMnO3/LaAlO3 superlattices

In this paper, we investigated the structural, electronic, and magnetic properties of SrMnO3/LaAlO3 (SMO/LAO) (001) heterostructures using density functional theory (DFT) with the Hubbard U correction, employing the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation within the Vienna Ab Initio Simulation Package (VASP). Three distinct superlattices—SMO1.5/LAO1.5, SMO1.5/LAO2, and SMO2.5/LAO1—were analyzed by varying the layer thicknesses to tailor their properties. The SMO1.5/LAO1.5 and SMO2.5/LAO1 superlattices exhibit antiferromagnetic (AFM) ground states, while the SMO1.5/LAO2 superlattice shows a ferromagnetic (FM) ground state. Electronic structure analysis reveals that SMO1.5/LAO1.5 and SMO1.5/LAO2 are metallic, whereas SMO2.5/LAO1 exhibits half-metallic behavior. By strategically controlling the layers in SMO/LAO heterostructures, it is promising to engineer electronic and magnetic properties that are important for developing advanced magnetic and nano-electronic devices.

Improving the Curie temperature of monolayer CrBr3 by Li adsorption: A first-principles study

The monolayer CrBr3, as an intrinsic magnetic semiconductor, holds great promise for future electronic and spintronic devices. However, the lower Curie temperature (TC) limits the applications. In this study, we investigated the impact of Li adsorption on the stability, electronic and magnetic properties of monolayer CrBr3 by performing first-principles calculations. Our results reveal that Li adsorption can lead to a semiconductor-to-half-metal transition, the spin-down band gap exhibits a linear variation in response to the adsorption coverage. Furthermore, Li adsorption can further enhance the Cr magnetic moment, and make the TC twice as large as that of pristine CrBr3. Significantly, the increase in TC derives from the competition between the stronger ferromagnetic superexchange among Cr-Br-Cr and the weaker direct antiferromagnetic exchange among Cr-Cr. Our results not only offer a simple and feasible approach to modulate the electronic structure and magnetism of monolayer CrBr3, but also may open up new prospects for utilizing monolayer CrBr3 in next-generation nanoelectronic and spintronic devices.

Graphitic Carbon Nitride: A Novel Two-Dimensional Metal-Free Carbon-Based Polymer Material for Electrochemical Detection of Biomarkers

Graphitic carbon nitride (g-C3N4) has gained significant attention due to its unique physicochemical properties as a metal-free, two-dimensional, carbon-based polymeric fluorescent substance composed of tris-triazine-based patterns with a slight hydrogen content and a carbon-to-nitrogen ratio of 3:4. It forms layered structures like graphite and demonstrates exciting and unusual physicochemical properties, making g-C3N4 widely used in nanoelectronic devices, spin electronics, energy storage, thermal conductivity materials, and many others. The biomedical industry has greatly benefited from its excellent optical, electrical, and physicochemical characteristics, such as abundance on Earth, affordability, vast surface area, and fast synthesis. Notably, the heptazine phase of g-C3N4 displays stable electronic bands. Another significant quality of this semiconductor material is its excellent fluorescence property, which is also helpful in preparing biosensors. Based on g-C3N4, electrochemical biosensors have provided better biocompatibility, higher sensitivity, low detection limits, nontoxicity, excellent selectivity, and surface versatility of functionalization for the delicate identification of target analytes. This review covers the latest studies on using efflorescent graphitic carbon nitride to fabricate electrochemical biosensors for various biomarkers. Carbon nitrides have been reported to possess excellent electroactivity properties, a massive surface-to-volume ratio, and hydrogen-bonding functionality, thus allowing electrochemical-based, highly sensitive, and selective detection platforms for an entire array of analytes. Considering the preceding information, this review addresses the fundamentals and background of g-C3N4 and its numerous synthesis pathways. Furthermore, the importance of electrochemical sensing of diverse biomarkers is emphasized in this review article. It also discusses the current status of the challenges and future perspectives of graphitic carbon nitride-based electrochemical sensors, which open paths toward their practical application in aspects of clinical diagnostics.

Reducing Si/Cu interfacial thermal resistance via hybrid CNT-graphene junctions: A molecular dynamics study

Covalently bonded carbon nanotube (CNT)-graphene hybrid junctions have garnered research attentions due to their potential applications in thermal management. This study comprehensively investigates the impact of CNT-graphene hybrid structures on thermal transport at the silicon/copper (Si/Cu) interface. Using non-equilibrium molecular dynamics (NEMD) simulations, we calculated the interfacial thermal resistance (ITR) of CNT/Si and CNT-graphene/Cu with different CNT diameters and surface densities, and evaluated the impact of CNT-graphene hybrid junction to the total thermal resistance across the Si/Cu interface. The MD results indicate that the overall thermal resistance of Si/CNT-graphene/Cu interfaces can be decreased by as much as 76.3 % relative to the Si/Cu interface. The effect of temperature on the interfacial thermal resistance were also revealed. Our findings provide insights for the design of novel nano-electronic devices with efficient thermal management.

Formation of vanadium dioxide nanocrystal arrays via post-growth annealing for stable and energy-efficient switches

The abrupt and reversible semiconductor-metal phase transition in vanadium dioxide nanocrystals has attracted considerable attention for potential applications in oxide electronics, including neuromorphic systems. This study presents a systematic investigation of post-growth annealing conditions for the formation of single VO2 M-phase nanocrystals arrays from VOx films synthesized by atomic layer deposition. The composition of the initial VOx films and the annealing parameters were found to significantly affect the morphology, phase composition and electrical properties of the obtained single nanocrystal arrays. Our results demonstrate that the formation of VO2 M-phase nanocrystal arrays occurs at annealing temperatures of 650 °C and above, irrespective of the initial film composition. More homogeneous in size nanocrystals are formed from initial VOx films with higher V+4 content. The structures with the initial V+4 content of 60 % annealed at 650 °C for 2 h demonstrates the resistive switching with an energy less than 150 fJ, and a total number of stable switching cycles more than 101⁰. Our results pave the way for the novel energy-efficient nanoelectronic and nanophotonic devices based on VO₂ nanoparticles.