Nanoelectronic Structures Research Articles

Investigation of the Robustness of Nanoelectronic Structures Based on Resonant Tunneling Elements

Investigation of the Robustness of Nanoelectronic Structures Based on Resonant Tunneling Elements

Nanosized Modification of the Silicon Surface by the Method of Focused Ion Beams

This paper presents the results of experimental studies of the modes of formation of nanosized structures on the surface of a silicon substrate by the method of focused ion beams (FIB). The regularities of the effect of the ion beam current, accelerating voltage, and radiation dose on the surface morphology of nanoscale structures are determined. The modes under which the effects of implantation swelling (structure height up to 3 nm) and etching (structure depth up to 8 nm) manifest themselves are determined. The average roughness of the resulting structures varies from 0.13 to 0.24 nm. The results can be used in the development of technology for manufacturing instrument structures in nanoelectronics and nanophotonics.

Preface

Due to recent pandemic, 2022 3rd International Conference on Mechanical Instrumentation and Automation (ICMIA 2022) was held virtually online during March 25-27, 2022. The decision to hold the virtual conference was made in compliance with many restrictions and regulations that were imposed by countries around the globe. Such restrictions were made to minimize the risk of people contracting or spreading the COVID-19 through physical contact. There were 80 individuals who attended this on-line conference, represented many countries including Malaysia, Singapore, Indonesia, Brazil and China. ICMIA 2022 is to bring together International Symposium on Mechanical Instrumentation and Automation to a common forum. And another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in International Symposium on Mechanical Instrumentation and Automation and related areas. During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In the second part, we invited four professors as our keynote speakers. Prof. Hamid Reza Karimi, Politecnico di Milano, Italy. His original research and development achievements span a broad spectrum within the topic of control systems, mechatronics, intelligent systems, and fault diagnosis with applications such as vehicles, robotics and manufacturing systems. And then we had Prof. Na Li, Xidian University, China. Her research focused on the error theory of electronic equipment, multi-scale electromechanical coupling problems, and the design and optimization of new nanoelectronic equipment structures. Assoc. Prof. Mohamed Arezki Mellal, M’Hamed Bougara University, Algeria. His research interests include developing new nature-inspired optimization methods for solving engineering problems of system dependability, design, manufacturing, and energy efficiency. Finally, we had Assoc. Prof. Lisu Yu, Nanchang University, China as our finale keynote speaker. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge. List of Committee member are available in this pdf.

Near-field infrared spectroscopy of SiOx nanowires

Scanning-probe-based patterning methods including local anodic oxidation have been widely used in nanotechnology to form various nanoelectronic device structures. However, so far spectroscopic investigations e.g. to determine the stoichiometry of oxide nanostructures with characteristic sizes below the diffraction limit do not exist. Using near-field infrared spectroscopy, we study the vibrational optical modes in SiOx nanowires with a height (width) of 2.1 nm (350 nm). The nanowires were produced by oxidation employing an atomic force microscope (AFM) on wide Si (111) terraces. The analysis of the spectroscopic data allows us to determine the composition of SiOx with a spatial resolution far below the diffraction limit. The composition × across SiOx nanowires is found to decrease from 1.6 in the center of the nanowire to 1.4 at its edges.

Quantitative scanning microwave microscopy of 2D electron and hole gases in AlN/GaN heterostructures

Although the scanning microwave microscope (SMM) is based on the atomic force microscope (AFM), the SMM differs from the AFM by being able to sense subsurface electromagnetic properties of a sample. This makes the SMM promising for in-depth nondestructive characterization of nanoelectronic structures. However, the SMM raw data are convoluted with the sample topography, making it especially challenging for quantitative characterization of nonplanar structures. In this paper, using the topography information simultaneously obtained by the AFM and the in situ extracted probe geometry, we de-embed from the topography-corrupted SMM data the sheet resistance of 2D electron or hole gas (2DEG or 2DHG) buried at the interface of an AlN/GaN heterostructure, including the lateral depletion of the 2DEG from an etched step. The SMM results are validated by Hall-effect measurements. The limitation and possible improvement in the present technique are discussed. With improved setup, the SMM can be used to nondestructively monitor the local sheet resistance of 2DEG or 2DHG during device manufacture. These studies help to pave the way to 3D microwave tomography on the nanometer scale.

Исследование робастности наноэлектронных структур на базе резонансно-туннельных элементов

Multi-input logic gates based on two-level logic cells MOBILE have short (picosecond) switching times and higher functionality due to the ability to implement logic functions with fewer gates. This creates good prospects for the development of ultra-high-speed FPGAs with a high degree of integration, which are required for organizing high-performance computing. However, the extremely high sensitivity of resonant tunneling elements to changes in the energies of quantum states requires an assessment of the stability of such structures to external influences in real operation. In this work, the problem of assessing the stability of nanoelectronic structures that include resonant tunneling elements is considered. The method for studying the robustness of logic cells MOBILE based on a resonant tunneling diode and an НВТ transistor was proposed, making it possible to find an external interval estimate of the output voltage of the device under study for given interval models of the initial components. The technique is based on the use of systems of topological and parametric equations written in finite increments. It was shown that the proposed decomposition principle for the initial interval model ensures the algorithmic solvability of the problem posed. A computational algorithm for calculating processes in a two-level logical cell MOBILE has been developed. The algorithm provides for step-by-step integration of interval differential equations and solution of interval nonlinear algebraic equations at each step of integration using Kaucher interval arithmetic. The obtained results of the study of processes in a two-level logic cell MOBILE create prerequisites for expanding the field of application of resonant tunneling devices in high-speed monolithic integrated circuits.

Twist-Dependent Electron Charge Transfer and Transport in Phosphorene–Graphene Heterobilayers

In this work, we explore the impact of twisting (rotational stacking) on the vertical charge transfer in a graphene–phosphorene bilayer using density functional theory (DFT) and on electron transport in the plane of the bilayer using DFT and the non-equilibrium Green’s function approach. We examine the bilayers with twist angles 0, 9.1, 13.3, and 44.1° and find a significant drop in charge transfer when the twist angle changes from 0 to >0°. We also identify an anisotropy of the current with regard to the twist angle, as well as direction, in the plane of the bilayer structures. Such interesting features could have an impact on enhancing the applications of two-dimensional twisted structures in nano-electronics.

First-principles computational exploration of ferromagnetism in monolayer GaS via substitutional doping

Using first-principles calculations, functionalization of the monolayer-GaS crystal structure through N or Cr-doping at all possible lattice sites has been investigated. Our results show that pristine monolayer-GaS is an indirect-bandgap, non-magnetic semiconductor. The bandgap can be tuned and a magnetic moment (MM) can be induced by the introduction of N or Cr atomic anion/cation doping in monolayer GaS. For instance, the intrinsic character of monolayer GaS can be changed by substitution of N for the S-site to p-type, while substitution of Cr at the S-site or Ga-site induces half-metallicity at sufficiently high concentrations. The defect states are located in the electronic bandgap region of the GaS monolayer. These findings help to extend the application of monolayer-GaS structures in nano-electronics and spintronics. Since the S-sites at the surface are more easily accessible to doping in experiment, we chose the S-site for further investigations. Finally, we perform calculations with ferromagnetic (FM) and antiferromagnetic (AFM) alignment of the MMs at the dopants. For pairs of impurities of the same species at low concentrations we find Cr atoms to prefer the FM state, while N atoms prefer the AFM state, both for impurities on opposite surfaces of the GaS monolayer and for impurities sharing a common Ga neighbor sitting at the same surface. Extending our study to higher concentrations of Cr atoms, we find that clusters of four Cr atoms prefer AFM coupling, whereas the FM coupling is retained for Cr atoms at larger distance arranged on a honeycomb lattice. For the latter arrangement, we estimate the FM Curie temperature T C to be 241 K. We conclude that the Cr-doped monolayer-GaS crystal structure offers enhanced electronic and magnetic properties and is an appealing candidate for spintronic devices operating close to room temperature.

Beam\u2013Plasma Discharge in Space and in a Lab

The process and applications of a specific type of gaseous discharge—beam–plasma discharge (BPD)—are reviewed. A brief survey of the BPD theory is presented. The basic features of BPD in active geophysical experiments with injection of electron beams into Earth’s ionosphere are discussed. Studies of the physics of BPD have revealed the effects successively applied in plasma technology for processing nanoelectronic materials and structures.

DNA origami

Biological materials are self-assembled with near-atomic precision in living cells, whereas synthetic 3D structures generally lack such precision and controllability. Recently, DNA nanotechnology, especially DNA origami technology, has been useful in the bottom-up fabrication of well-defined nanostructures ranging from tens of nanometres to sub-micrometres. In this Primer, we summarize the methodologies of DNA origami technology, including origami design, synthesis, functionalization and characterization. We highlight applications of origami structures in nanofabrication, nanophotonics and nanoelectronics, catalysis, computation, molecular machines, bioimaging, drug delivery and biophysics. We identify challenges for the field, including size limits, stability issues and the scale of production, and discuss their possible solutions. We further provide an outlook on next-generation DNA origami techniques that will allow in vivo synthesis and multiscale manufacturing.

АНАЛИЗ ДИНАМИЧЕСКИХ ПРОЦЕССОВ В НАНОЭЛЕКТРОННЫХ СТРУКТУРАХ НА БАЗЕ МЕМРЕЗИСТИВНЫХ ЭЛЕМЕНТОВ

The emergence of recently a wide range of nanoelectronic components is expanding the possibilities of information and computing systems. First of all, it concerns supercomputers with Petaflopovaya productivity. To achieve such performance on the basis of modern microelectronic devices, computing complexes are created, combining up to 100 thousand processors that consume about 100 megawatts of electrical energy and occupy about 300 square meters. A significant increase in productivity, reduction of energy consumption and a decrease in mass-dimensional indicators can be ensured in the transition from microelectronic to a nanoelectronic element base. For such promising nanoelectronic components include memristors. A memristor (from memory — memory, and resistor-electrical resistance) is a passive element in microelectronics that can change its resistance depending on the charge flowing through it. For a long time, the memristor was considered a theoretical model [7], which cannot be implemented in practice, until the first sample of the element demonstrating the properties of the memristor was created in 2008 by a team of scientists led by R. S. Williams in the research laboratory of Hewlett-Packard. The device does not store charge like a capacitor, does not support magnetic flux like an inductor. The change in the properties of the device is provided by chemical reactions in a thin two-layer film of titanium dioxide (5 nm). One layer of the device film is slightly depleted of oxygen and oxygen vacancies migrate between the layers when the voltage changes. This implementation of the memristor belongs to the class of nanoion devices. The observed phenomenon of hysteresis in the memristor allows it to be used, among other things, as a memory cell [9, 10-15, 20-21]. The already studied properties of memristors allow us to say that on their basis it is possible to create computers of a fundamentally new architecture, significantly exceeding semiconductor ones in performance. Due to the regular structure of intersecting nanowires, memristor fabrication is quite simple, especially in comparison with the complex structure of modern processors based on CMOS technology. As a result, the write / read time in the memristor memory cell does not exceed 5 ns. The number of read / write cycles exceeds 1012, and the storage time of information is more than 10 years. All this suggests that memristor memory will become the only type of computer memory. However, the use of such elements in real-life conditions leads to the fact that the electrical parameters of these devices vary over a wide range. This uncertainty in characteristics complicates circuit analysis and the entire design process for electronic devices that include memristor components. In this regard, the problem of assessing the stability of nanoelectronic structures based on memresistive elements under conditions of uncertain external influences is urgent.

Atomic force microscopy for nanoscale mechanical property characterization

Over the past several decades, atomic force microscopy (AFM) has advanced from a technique used primarily for surface topography imaging to one capable of characterizing a range of chemical, mechanical, electrical, and magnetic material properties with subnanometer resolution. In this review, we focus on AFM as a nanoscale mechanical property characterization tool and examine various AFM contact and intermittent contact modes that add mechanical contrast to an imaged surface. Through detailed analysis of the tip-sample contact mechanics, this contrast can be converted into quantitative measurements of various nanomechanical properties including elastic modulus, shear modulus, wear rate, adhesion, and viscoelasticity. Different AFM modes that provide such measurements are compared and contrasted in this work on a wide range of materials including ceramics, metals, semiconductors, polymers, and biomaterials. In the last few years, considerable improvements have been made in terms of fast imaging capabilities, tip preservation, and quantitative mechanics for multifrequency measurements as well as well-known AFM modes like amplitude modulation and peak-force tapping. In line with these developments, a major highlight of this review is the discussion of the operation and capabilities of one such mode, namely, intermittent contact resonance AFM (ICR-AFM). The applications of ICR-AFM to nanoscale surface and subsurface quantitative mechanical characterizations are reviewed with specific examples provided for thin polymeric films and patterned nanostructures of organosilicate dielectric materials. The combination of AFM-based mechanical characterization with AFM-based chemical spectroscopy to allow nanoscale structure-property characterization is also discussed and demonstrated for the analysis of low-k dielectric/copper nanoelectronic interconnect structures and further highlights synergistic advances in the AFM field.

Atomic imaging of mechanically induced topological transition of ferroelectric vortices

Ferroelectric vortices formed through complex lattice–charge interactions have great potential in applications for future nanoelectronics such as memories. For practical applications, it is crucial to manipulate these topological states under external stimuli. Here, we apply mechanical loads to locally manipulate the vortices in a PbTiO3/SrTiO3 superlattice via atomically resolved in-situ scanning transmission electron microscopy. The vortices undergo a transition to the a-domain with in-plane polarization under external compressive stress and spontaneously recover after removal of the stress. We reveal the detailed transition process at the atomic scale and reproduce this numerically using phase-field simulations. These findings provide new pathways to control the exotic topological ferroelectric structures for future nanoelectronics and also valuable insights into understanding of lattice-charge interactions at nanoscale.

Formation of hierarchical structures from functionalized multi-walled carbon nanotubes in aerosil containing solutions

Specific features and regularities of self-assembly and self-organization of multi-walled carbon nanotubes (MWCNT) have been studied for diffusion-limited conditions (method of drops) in water-based (deionized water) colloidalal solutions with aerosil exposed to DC electric fields with magnitudes of 15 to 25 V. Studies of hierarchical structure formation during drop evaporation in uniform electric fields have revealed the formation of 40–120 nm sized linear piecewise formations, 25–45 nm sized fractal structures and 250 nm sized diffuse structures from MWCNT – COOH + aerosil + H2Odw. The structures have been studied using confocal microscopy, X-ray diffraction, Raman scattering, atomic force microscopy, IR spectroscopy and scanning electron microscopy. The sizes of the observed micro- and nanostructures decrease following the hyperbolic law d = 1/U in the approximation d → 2R, their growth rate increasing as U2. We show that intense ultrasonication of functionalized MWCNT – COOH + aerosil + H2Odw in colloidal solutions causes the formation of the so-called “breathing" modes in axis centered single-walled carbon nanotubes. This is confirmed by short-wave Raman scattering excitation and enables the existence of both combined sp2-hybridization types with π- and σ- carbon bonds and the metallic and semiconductor conductivity types in the material thus showing good promise of these structures for nanoelectronics.

Tripentaphenes: two-dimensional acepentalene-based nanocarbon allotropes.

Tripentaphenes are 2D nanocarbon lattices conceptually obtained from the assembly of acepentalene units. In this work, density functional theory is used to investigate their structural, electronic, and vibrational properties. Their bonding configuration is rationalized with a resonance mechanism, which is unique to each of the 2D assemblies. Their formation energies are found to lie within the range of other previously synthesized carbon nanostructures and phonon calculations indicate their dynamical stability. In addition, all studied tripentaphenes are metallic and display different features (e.g., Dirac cone) depending on the details of the atomic structure. The resonance structure also plays an important role in determining the electronic properties as it leads to delocalized electronic states, further highlighting the potential of the structures in nanoelectronics.

Graphene Nanoribbon Based Complementary Logic Gates and Circuits

As CMOS feature size is reaching atomic dimensions, unjustifiable static power, reliability, and economic implications are exacerbating, thereby prompting for conducting research on new materials, devices, and/or computation paradigms. Within this context, graphene nanoribbons (GNRs), owing to graphene's excellent electronic properties, may serve as basic structures for carbon-based nanoelectronics. In this paper, we make use of the fact that GNR behavior can be modulated via top/back gate contacts to mimic a given functionality and combine complementary GNRs for constructing Boolean gates. We first introduce a generic gate structure composed of a pull-up GNR performing the gate Boolean function and a pull-down GNR performing its complement. Then, we seek GNR dimensions and gate topologies required for the design of 1-, 2-, and 3-input graphene-based Boolean gates, validate the proposed gates by means of SPICE simulation, which makes use of a non-equilibrium Green's function Landauer formalism based Verilog-A model to calculate GNR conductance, and evaluate their performance with respect to propagation delay, power consumption, and active area footprint. Simulation results indicate that, when compared with 7 nm FinFET CMOS counterparts, the proposed gates exhibit $\text{6}\times$ to 2 orders of magnitude smaller propagation delay, 2 to 3 orders of magnitude lower power consumption, and necessitate 2 orders of magnitude smaller active area footprint. We further present full adder (FA) and SRAM cell GNR designs, as they are currently fundamental components for the construction of any computation system. For an effective FA implementation, we introduce a 3-input MAJORITY gate, which apart of being able to directly compute FA's carry-out is an essential element in the implementation of error correcting codes codecs, which outperforms the CMOS equivalent carry-out calculation circuit by 2 and 3 orders of magnitude in terms of delay and power consumption, respectively, while requiring 2 orders of magnitude less area. The proposed FA exhibits $\text{6.2}\times$ smaller delay, 3 orders of magnitude less power consumption, while requiring 2 orders of magnitude less area, when compared with the 7 nm FinFET CMOS counterpart. However, because of the effective carry-out circuitry, a GNR-based $n$-bit ripple carry adder, whose performance is linear in the carry-out path, will be $\text{108}\times$ faster than an equivalent CMOS implementation. The GNR-based SRAM cell provides a slightly better resilience to dc-noise characteristics, while performance-wise has a $\text{3.6}\times$ smaller delay, consumes 2 orders of magnitude less power, and requires 1 order of magnitude less area than the CMOS equivalent. These results clearly indicate that the proposed GNR-based approach is opening a promising avenue toward future competitive carbon-based nanoelectronics.

Detection of gas molecule using C3N island single electron transistor

C3N is a recently discovered 2D layered material structurally similar to graphene, which has demonstrated immense prospect for future nanoelectronics. In this work, we have designed and investigated the operation and performance of a C3N island single electron transistor (SET) for the first time. Using First-principles based calculations, we investigated the effect of various molecular adsorptions on the electronic and conduction behaviour of the SET. C3N was found to be the perfect host material for capturing CO2. The charge stability diagram carries the signature of different molecules within the SET and their presence can be uniquely identified from various line scans and normalised differential conductance behaviour obtained from it. Our results suggest the usefulness of such nanoelectronic structures for sensing toxic gas molecules which can be operational over a wide temperature range with detection sensitivity upto a single molecular level.

Quantum theory of terahertz conductivity of semiconductor nanostructures

Efficient and controlled charge carrier transport through nanoelements is currently a primordial question in the research of nanoelectronic materials and structures. We develop a quantum-mechanical theory of the conductivity spectra of confined charge carriers responding to an electric field from dc regime up to optical frequencies. The broken translation symmetry induces a broadband drift-diffusion current, which is not taken into account in the analysis based on Kubo formula and relaxation time approximation. We show that this current is required to ensure that the dc conductivity of isolated nanostructures correctly attains zero. It causes a significant reshaping of the conductivity spectra up to terahertz or multiterahertz spectral ranges, where the electron scattering rate is typically comparable to or larger than the probing frequency.

Tuning the electronic properties of the fullerene C20 cage via silicon impurities

The fullerene C20 represents one of the most active classes of nanostructures, and they have been widely used as active materials for important applications. In this study, we investigate and discuss the tuning of the electronic properties of the fullerene C20 cage via various consternations and locations of silicon atoms. All calculations are based on the density functional theory (DFT) at the B3LYP/3-21G level through the Gaussian 09W program package. The optimized structures, density of state (DOS) analysis, total energies, dipole moments, HOMO energies, Fermi level energies, LUMO energies, energy gaps, and the work functions were performed and discussed. Our results show that the electronic properties of C20 cage do not only depend on the silicon impurity concentrations, but also depend on the geometrical pattern of silicon impurities in the C20 cage. The tuning of the electronic properties leads to significant changes in the charge transport and the absorption spectra for C20 cage via engineering the energy gap. So, we suggest that substitutional impurities are the best viable option for enhancement of desired electronic properties of C20 cage for using these structures in nanoelectronics and solar cell applications.

Mesoporous thin film structures as metal nanoparticle reactors for electronic circuits: Effects of matrix crystallinity and nanoparticle functionalization

There is an increasing interest in versatile nanoelectronic structures based on stable, accessible and spatially located arrays of metal nanoparticles. In this study, the influences of mesoporous titania thin film crystallinity and pore features over electrical conductivity of embedded Ag-nanoparticles were analyzed. Although matrices treated at lower temperatures have shown less pore connectivity, less extensive anatase fraction and lower silver content, they revealed higher electrical conductivity than matrices treated at higher temperatures. This was interpreted as better connectivity among particles from plasmon behavior. The stability of this system was significantly enhanced through upon chemisorption of 1-octanethiol self-assemble monolayers over Ag-nanoparticles. The maximum plasmon absorbance remained practically unaltered after storage for at least 15 days and the current remains stable up to 20 voltage cycles. This demonstrates that a stable and accessible conductive nanocomposite circuit consisting of alkanethiol-functionalized metal nanoparticles embedded in a mesoporous oxide thin film matrix can be produced.