Search Results (42)

In this work, a theoretical study on the combined effects of an external electric field and a nonresonant intense laser field on the electronic properties of a quantum dot with a truncated cone shape is presented. This quantum dot was made from a type-II CdTe/CdSe heterostructure (core/shell). Using the effective mass approximation with parabolic bands and the finite element method, the Schrödinger equation was solved to analyze the confined states of electron, hole, and exciton. This study demonstrates the potential of combining nonresonant intense laser and electric fields to control confinement properties in semiconductor nanodevices, with potential applications in optoelectronics and quantum mechanics-related technologies. Full article

The transport properties of one-dimensional van der Waals nanodevices composed of carbon nanotubes (CNTs), hexagonal boron nitride (hBN) nanotubes, and molybdenum dichalcogenide (MoX₂) nanotubes were investigated within the framework of density functional theory (DFT). It was found that in nanodevices based on MoS₂(24,24) and MoTe₂(24,24), the effect of resonant tunneling is suppressed due to electron–phonon scattering. This suppression arises from the fact that these materials are semiconductors with an indirect band gap, where phonon participation is required to conserve momentum during transitions between the valence and conduction bands. In contrast, nanodevices incorporating MoSe₂(24,24), which possesses a direct band gap, exhibit resonant tunneling, as quasiparticles can tunnel between the valence and conduction bands without a change in momentum. It was demonstrated that the presence of vacancy defects in the CNT segment significantly degrades quasiparticle transport compared to Stone–Wales (SW) defects. Furthermore, it was revealed that resonant interactions between SW defects in MoTe₂(24,24)–hBN(27,27)–CNT(24,24) nanodevices can enhance the differential conductance under certain voltages. These findings may be beneficial for the design and development of nanoscale diodes, back nanodiodes, and tunneling nanodiodes. Full article

In this work, the optical and electronic characteristics of MoS₂(n,n) and MoSe₂(n,n) nanotubes and 1D van der Waals nanoheterostructures based on them are determined from first principles. It is shown that with an increase in the diameters of MoS₂(n,n) and MoSe₂(n,n) nanotubes, their bandgaps increase (in MoS₂(n,n), the gap varies from 0.27 eV to 1.321 eV, and in MoSe₂(n,n) from 0.153 eV to 1.216 eV). It was found that with an increase in the diameter of the nanotubes, the static permittivity decreases; van der Waals nanostructures of MoS₂(8,8)@MoSe₂(16,16) and MoS₂(6,6)@MoSe₂(14,14) consisting of coaxially compound MoS₂(8,8) and MoSe₂(16,16), MoS₂(6,6) and MoSe₂(14,14), respectively, have high static dielectric permittivitiesof 6. 5367 and 3.0756. Such nanoheterostructures offer potential for developing various nanoelectronic devices due to the possibility of effective interaction with an electric field. Studies revealed that the van der Waals nanostructures MoSe₂(6,6)@MoS₂(14,14) and MoSe₂(8,8)@MoS₂(16,16) exhibit a semiconductor nature with bandgap widths of 0.174 eV and 0.53 eV, respectively, and MoS₂(6,6)@MoSe₂(14,14) and MoS₂(8,8)@MoSe₂(16,16) exhibit metallic properties. Stepped areas of Coulomb origin with a constant period at a voltage of 0.448 V appear on the current–voltage characteristic of the van der Waals nanoheterodevices. It is found that MoSe₂(6,6)@MoS₂(14,14) and MoSe₂(8,8)@MoS₂(16,16) nanodevices transmit electric current preferentially in the forward direction due to the formation of a nanoheterojunction between semiconductor nanotubes with different forbidden band values. The fundamental regularities obtained during the study can be useful for the further development of electronic components of nano- and microelectronics. Full article

The continuous scaling down of MOSFETs is one of the present trends in semiconductor devices to increase device performance. Nevertheless, with scaling down beyond 22 nm technology, the performance of even the newer nanodevices with multi-gate architecture declines with an increase in short channel effects (SCEs). Consequently, to facilitate further increases in the drain current, the use of strained silicon technology provides a better solution. Thus, the development of a novel Gate-All-Around Field-Effect Transistor (GAAFET) incorporating a strained silicon channel with a 10 nm gate length is initiated and discussed. In this device, strain is incorporated in the channel, where a strained silicon germanium layer is wedged between two strained silicon layers. The GAAFET device has four gates that surround the channel to provide improved control of the gate over the strained channel region and also reduce the short channel effects in the devices. The electrical properties, such as the on current, off current, threshold voltage (V_TH), subthreshold slope, drain-induced barrier lowering (DIBL), and I_on/I_off current ratio, of the 10 nm channel length GAAFET are compared with the 22 nm strained silicon channel GAAFET, the existing SOI FinFET device on 10 nm gate length, and IRDS 2022 specifications device. The developed 10 nm channel length GAAFET, having an ultrathin strained silicon channel, delivers enriched device performance, being augmented in contrast to the IRDS 2022 specifications device, showing improved characteristics along with amended SCEs. Full article

Two-dimensional (2D) semiconductor components have excellent physical attributes, such as excellent mechanical ductility, high mobility, low dielectric constant, and tunable bandgap, which have attracted much attention to the fields of flexible devices, optoelectronic conversion, and microelectronic devices. Additionally, one-dimensional (1D) semiconductor materials with unique physical attributes, such as high surface area and mechanical potency, show great potential in many applications. However, isolated 1D and 2D materials often do not meet the demand for multifunctionality. Therefore, more functionality is achieved by reconstructing new composite structures from 1D and 2D materials, and according to the current study, it has been demonstrated that hybrid dimensional integration yields a significant enhancement in performance and functionality, which is widely promising in the field of constructing novel electronic and optoelectronic nanodevices. In this review, we first briefly introduce the preparation methods of 1D materials, 2D materials, and 1D/2D heterostructures, as well as their advantages and limitations. The applications of 1D/2D heterostructures in photodetectors, gas sensors, pressure and strain sensors, as well as photoelectrical synapses and biosensors are then discussed, along with the opportunities and challenges of their current applications. Finally, the outlook of the emerging field of 1D/2D heterojunction structures is given. Full article

In this paper, we propose an ultrascaled WS₂ field-effect transistor equipped with a Pd/Pt sensitive gate for high-performance and low-power hydrogen gas sensing applications. The proposed nanosensor is simulated by self-consistently solving a quantum transport equation with electrostatics at the ballistic limit. The gas sensing principle is based on the gas-induced change in the metal gate work function. The hydrogen gas nanosensor leverages the high sensitivity of two-dimensional WS2 to its sur-rounding electrostatic environment. The computational investigation encompasses the nanosensor’s behavior in terms of potential profile, charge density, current spectrum, local density of states (LDOS), transfer characteristics, and sensitivity. Additionally, the downscaling-sensitivity trade-off is analyzed by considering the impact of drain-to-source voltage and the electrostatics parameters on subthreshold performance. The simulation results indicate that the downscaling-sensitivity trade-off can be optimized through enhancements in electrostatics, such as utilizing high-k dielectrics and reducing oxide thickness, as well as applying a low drain-to-source voltage, which also contributes to improved energy efficiency. The proposed nanodevice meets the prerequisites for cutting-edge gas nanosensors, offering high sensing performance, improved scaling capability, low power consumption, and complementary metal–oxide–semiconductor compatibility, making it a compelling candidate for the next generation of ultrascaled FET-based gas nanosensors. Full article

This research presents a comprehensive study of a Schottky diode fabricated using a gold wafer and a bilayer molybdenum disulfide (${\mathrm{MoS}}_2$) film. Through detailed simulations, we investigated the electric field distribution, potential profile, carrier concentration, and current–voltage characteristics of the device. Our findings confirm the successful formation of a Schottky barrier at the Au/${\mathrm{MoS}}_2$ interface, characterized by a distinct nonlinear I–V relationship. Comparative analysis revealed that the Au/${\mathrm{MoS}}_2$ diode significantly outperforms a traditional W/Si structure in terms of rectification performance. The Au/${\mathrm{MoS}}_2$ diode exhibited a current density of 1.84 × ${10}^{-9}$ A/${\mathrm{cm}}^2$, substantially lower than the 3.62 × ${10}^{-5}$ A/${\mathrm{cm}}^2$ in the W/Si diode. Furthermore, the simulated I–V curves of the Au/${\mathrm{MoS}}_2$ diode closely resembled the ideal diode curve, with a Pearson correlation coefficient of approximately 0.9991, indicating an ideality factor near 1. A key factor contributing to the superior rectification performance of the Au/${\mathrm{MoS}}_2$ diode is its higher Schottky barrier height of 0.9 eV compared to the 0.67 eV of W/Si. This increased barrier height is evident in the band diagram analysis, which further elucidates the underlying physics of Schottky barrier formation in the Au/${\mathrm{MoS}}_2$ junction. This research provides insights into the electronic properties of Schottky contacts based on two-dimensional ${\mathrm{MoS}}_2$, particularly the relationship between electronic barriers, system dimensions, and current flow. The demonstration of high-ideality-factor Au/${\mathrm{MoS}}_2$ diodes contributes to the design and optimization of future electronic and optoelectronic devices based on 2D materials. These findings have implications for advancements in semiconductor technology, potentially enabling the development of smaller, more efficient, and flexible devices. Full article

One of the most advanced and versatile nanoscale diagnostic tools is atomic force microscopy. By enabling advanced imaging techniques, it allows us to determine various assets of a surface, including morphological, electrical, mechanical, magnetic, and thermal properties. Measuring local current flow is one of the very important methods of evaluation for, for instance, photovoltaic materials or semiconductor structures and other nanodevices. Due to contact areas, the current densities can easily reach above 1 kA/m²; therefore, special detection/measurement setups are required. They meet the required measurement range, sensitivity, noise level, and bandwidth at the measurement scale. Also, they prevent the sample from becoming damaged and prevent unwanted tip–sample issues. In this paper, we present three different nanoscale current measurement solutions, supported with test results, proving their performance. Full article

Recently, the application of two–dimensional (2D) piezoelectric materials has been seriously hindered because most of them possess only in–plane piezoelectricity but lack out–of–plane piezoelectricity. In this work, using first–principles calculation, by atomic substitution of penta–graphene (PG) with tiny out–of–plane piezoelectricity, we design and predict stable 2D X–PG (X = Si or Ge) semiconductors with excellent in–plane and out–of–plane piezoelectricity and extremely high in–plane hole mobility. Among them, Ge–PG exhibits better performance in all aspects with an in–plane strain piezoelectric coefficient d₁₁ = 8.43 pm/V, an out–of–plane strain piezoelectric coefficient d₃₃ = −3.63 pm/V, and in–plane hole mobility μ_h = 57.33 × 10³ cm² V⁻¹ s⁻¹. By doping Si and Ge atoms, the negative Poisson’s ratio of PG approaches zero and reaches a positive value, which is due to the gradual weakening of the structure’s mechanical strength. The bandgaps of Si–PG (0.78 eV) and Ge–PG (0.89 eV) are much smaller than that of PG (2.20 eV), by 2.82 and 2.47 times, respectively. This indicates that the substitution of X atoms can regulate the bandgap of PG. Importantly, the physical mechanism of the out–of–plane piezoelectricity of these monolayers is revealed. The super–dipole–moment effect proposed in the previous work is proved to exist in PG and X–PG, i.e., it is proved that their out–of–plane piezoelectric stress coefficient e₃₃ increases with the super–dipole–moment. The e₃₃–induced polarization direction is also consistent with the super–dipole–moment direction. X–PG is predicted to have prominent potential for nanodevices applied as electromechanical coupling systems: wearable, ultra–thin devices; high–speed electronic transmission devices; and so on. Full article

Directional ionic migration in ultra-thin metal-oxide semiconductors under applied electric fields is a key mechanism for developing various electronic nanodevices. However, understanding charge transfer dynamics is challenging due to rapid ionic migration and uncontrolled charge transfer, which can reduce the functionality of microelectronic devices. This research investigates the supercapacitive-coupled memristive characteristics of ultra-thin heterostructured metal-oxide semiconductor films at TiO₂-In₂O₃/Au Schottky junctions. Using atomic layer deposition (ALD), we nano-engineered In₂O₃/Au-based metal/semiconductor heterointerfaces. TEM studies followed by XPS elemental analysis revealed the chemical and structural characteristics of the heterointerfaces. Subsequent AFM studies of the hybrid heterointerfaces demonstrated supercapacitor-like behavior in nanometer-thick TiO₂-In₂O₃/Au junctions, resembling ultra-thin supercapacitors, pseudocapacitors, and nanobatteries. The highest specific capacitance of 2.6 × 10⁴ F.g⁻¹ was measured in the TiO₂-In₂O₃/Au junctions with an amorphous In₂O₃ electron gate. Additionally, we examined the impact of crystallization, finding that thermal annealing led to the formation of crystalline In₂O₃ films with higher oxygen vacancy content at TiO₂-In₂O₃ heterointerfaces. This crystallization process resulted in the evolution of non-zero I-V hysteresis loops into zero I-V hysteresis loops with supercapacitive-coupled memristive characteristics. This research provides a platform for understanding and designing adjustable ultra-thin Schottky junctions with versatile electronic properties. Full article

Two-dimensional (2D) van der Waals layered materials have been explored in depth. They can be vertically stacked into a 2D heterostructure and represent a fundamental way to explore new physical properties and fabricate high-performance nanodevices. However, the controllable and scaled growth of non-layered quasi-2D materials and their heterostructures is still a great challenge. Here, we report a selective two-step growth method for high-quality single crystalline CrTe/WSe₂ and CrTe/MoS₂ heterostructures by adopting a universal CVD strategy with the assistance of molten salt and mass control. Quasi-2D metallic CrTe was grown on pre-deposited 2D transition metal dichalcogenides (TMDC) under relatively low temperatures. A 2D CrTe/TMDC heterostructure was established to explore the interface’s structure using scanning transmission electron microscopy (STEM), and also demonstrate ferromagnetism in a metal–semiconductor CrTe/TMDC heterostructure. Full article

Conventional optical microscopes are only able to resolve objects down to a size of approximately 200 nm due to optical diffraction limits. The rapid development of nanotechnology has increased the demand for greater imaging resolution, with a need to break through those diffraction limits. Among super-resolution techniques, microsphere imaging has emerged as a strong contender, offering low cost, simple operation, and high resolution, especially in the fields of nanodevices, biomedicine, and semiconductors. However, this technology is still in its infancy, with an inadequate understanding of the underlying principles and the technology’s limited field of view. This paper comprehensively summarizes the status of current research, the advantages and disadvantages of the basic principles and methods of microsphere imaging, the materials and preparation processes, microsphere manipulation methods, and applications. The paper also summarizes future development trends. Full article

Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs. Full article

Equilibrium geometries and properties of self-assembled (InN)_12n (n = 1–9) nanoclusters (nanowires and nanosheets) are studied using the GGA-PBE (general gradient approximation with Perdew–Burke–Ernzerh) method. The relative stabilities and growth patterns of semiconductor (InN)_12n nanoclusters are investigated. The odd-numbered nano-size (InN)_12n (n is odd) have weaker stabilities compared with the neighboring even-numbered (InN)_12n (n is even) ones. The most stable (InN)₄₈ nanosheet is selected as a building unit for self-assembled nano-size film materials. In particular, the energy gaps of InN nanoclusters show an even–odd oscillation and reflect that (InN)_12n (n = 1–9) nanoclusters are good optoelectronic materials and nanodevices due to their energy gaps in the visible region. Interestingly, the calculated energy gaps for (InN)_12n nanowires varies slightly compared with that of individual (InN)₁₂ units. Additionally, the predicted natural atomic populations of In atoms in (InN)_12n nanoclusters show that the stabilities of (InN)_12n nanoclusters is enhanced through the ionic bonding and covalent bonding of (InN)_12n (n = 1–9) nanoclusters. Full article

Semiconductor nanocrystals (NCs) hold immense potential as luminescent materials for various optoelectronic applications. While significant progress has been made in developing NCs with outstanding optical properties in the visible range, their counterparts emitting in the ultraviolet (UV) spectrum are less developed. Rb₂AgI₃ is a promising UV-emitting material due to its large band gap and high stability. However, the optical properties of low-dimensional Rb₂AgI₃ NCs are yet to be thoroughly explored. Here, we synthesized Rb₂AgI₃ NCs via a hot injection method and investigated their properties. Remarkably, these NCs exhibit UV luminescence at 302 nm owing to self-trapped excitons. The wide-bandgap nature of Rb₂AgI₃ NCs, combined with their intrinsic UV luminescence, offers considerable potential for applications in UV photonic nanodevices. Our findings contribute to the understanding of Rb₂AgI₃ NCs and pave the way for exploiting their unique properties in advanced optoelectronic systems. Full article