Small Device Size Research Articles

Tunneling Current Variations in Small-Sized Devices Based on a Compact Threshold Voltage Model

Accurate modeling of threshold voltage is necessary in the integrated circuit design of strained silicon devices. Thoroughly researching the factors that affect threshold voltage and establishing a more precise threshold voltage model, can provide essential theoretical support for integrated circuit design. By solving a Poisson equation, in this paper, we demonstrate a comprehensive physical model for the threshold voltage of strained Si NMOSFETs using the gradual channel approximation theory and a quasi-two-dimensional analysis. The model investigates the physical effects such as short-channel, narrow-channel, non-uniform doping, and drain-induced barrier lowering effects on the threshold voltage. After substituting the extracted parameters into the model, a comparison was made with experimental results to validate the accuracy and correctness of the established model. Additionally, variations in the tunneling current of small-sized devices were studied. The two models provide essential references for the analysis and design of strained Si large-scale integrated circuits.

A Review of Acoustic Devices Based on Suspended 2D Materials and Their Composites

AbstractAcoustic devices play an increasingly important role in modern society for information technology and intelligent systems, and recently significant progress has been made in the development of communication, sensing, and energy transduction applications. However, conventional material systems, such as polymers, metals and silicon, show limitations to fulfill the evolving requirements for high‐performance acoustic devices of small size, low power consumption, and multifunctional capabilities. 2D materials hold the promise in overcoming the development bottleneck of acoustic devices aforementioned, given their atomic‐thin thickness, extensive surface area, superior physical properties, and remarkable layer‐stacking tunability. By suspending the 2D materials, mechanical and thermal disruption from substrate will be eliminated, which will enable the development of new classes of acoustic devices with unprecedented sensitivity and accuracy. In this review, the recent progress of acoustic devices based on suspended 2D materials and their composites, especially applications in the audio frequency, static pressure, and ultrasonic frequency range, is briefly summarized, emphasizing the advantageous properties of suspended 2D materials and related outstanding device performance. Together with the development of 2D membrane synthesis, transfer, as well as microelectromechanical fabrication process, suspended 2D materials will shed light on the next‐generation high‐performance acoustic devices.

Optimization of Ultra-Wideband bandwidth for the design of microstrip monopole antennas using Defected Ground Structure and star-shaped patche

This paper presents a design of a monopole microstrip antenna developed to support Ultra-wideband (3.1 -10.6 GHz) technology wireless communication systems. An antenna with minimalist dimensions operates on C-Band (wireless LAN) and X-Band (downlink satellite) frequencies. The antenna profile has a star shape patch on the top side and the use of the Defected Ground Structure (DGS) technique on the bottom side on RT DUROID substrate media. The design uses a simulation method using software and measurement tests on antenna prototypes to obtain parameters and antenna performance characteristics. The results of the measurement test, the bandwidth return loss < -10 dB has a difference of 40% (absolute) and 0.7% (Fractional) lower than the simulation when VSWR < 2. The radiation pattern forms an omnidirectional with a maximum directivity (Gain) of 5.18dBi with polarization vertical. Overall, the UWB monopole antenna design results have a low profile, compact, small size, and support mobile communication devices.

Visualizing Interfacial Energy Offset and Defects in Efficient 2D/3D Heterojunction Perovskite Solar Cells and Modules.

Currently, the full potential of perovskite solar cells (PSCs) is limited by chargecarrier recombination owing to imperfect passivation methods. Here, the recombination loss mechanisms owing to the interfacial energy offset and defects are quantified. The results show that a favorable energy offset can reduce minority carriers and suppress interfacial recombination losses more effectively than chemical passivation. To obtain high-efficiency PSCs, 2D perovskites are promising candidates, which offer powerful field effects and require only modest chemical passivation at the interface. The enhanced passivation and charge-carrier extraction offered by the 2D/3D heterojunction PSCs has boosted their power conversion efficiency to 25.32% (certified 25.04%) for small-size devices and to 21.48% for a large-area module (with a designated area of 29.0cm2 ). Ion migration is also suppressed by the 2D/3D heterojunction, such that the unencapsulated small-size devices maintain 90% of their initial efficiency after 2000h of continuous operation at the maximum power point.

Valine-Modified PbI2 for the Growth of Pinhole-Free Lead Halide Perovskite Thin Films by Vapor–Solid Reaction

In recent years, the efficiency of perovskite solar cells (PSCs) has rapidly increased, making PSCs commercially viable and able to compete with silicon solar cells. However, the technology for large-scale production of perovskite thin films still poses a significant challenge to the commercialization of PSCs. This is mainly because the thickness of the perovskite light-absorbing film is less than 1 μm and easily produces pinholes during large-scale production, causing serious charge recombination and reducing the efficiency of the device. As a result, the efficiencies of most large-scale PSC modules are significantly lower than those of small-size devices. Vapor-reaction technology is considered a crucial method to enhance the uniformity of perovskite thin films. However, current techniques are not yet advanced enough to deposit pinhole-free perovskite thin films on a large scale. One major challenge is that lead iodide (PbI2) precursor thin films have a tendency to develop a sheet-like structure with a loose morphology, which contributes to the formation of pinholes in the perovskite film. Additionally, uncoordinated Pb2+ could be easily generated in the PbI2 film during thermal evaporation, causing an increase in trap-states in the perovskite crystal. To address this, we developed a valine treatment process in this study to change the preferred orientation of PbI2 from a sheet-like to a particle-like aggregate and obtained compact PbI2 thin films. Meanwhile, this valine vapor treatment can significantly reduce the uncoordinated Pb2+ in PbI2 films. Based on this, we successfully prepared pinhole-free perovskite thin films using a vapor–solid reaction. Perovskite films based on these valine-treated PbI2 exhibited a reduced trap density and significantly improved PSCs’ performance, with a maximum efficiency exceeding 21%. Large-area PSC mini-modules (5 cm × 5 cm) produced from the perovskite film (30 cm × 30 cm) showed uniformly distributed power conversion efficiency values exceeding 17%, with the highest value reaching 18.78%. We believe that this facile valine vapor treatment holds great potential for the large-scale production of stable and high-efficiency PSC modules.

An organ-on-chip device with integrated charge sensors and recording microelectrodes

Continuous monitoring of tissue microphysiology is a key enabling feature of the organ-on-chip (OoC) approach for in vitro drug screening and disease modeling. Integrated sensing units are particularly convenient for microenvironmental monitoring. However, sensitive in vitro and real-time measurements are challenging due to the inherently small size of OoC devices, the characteristics of commonly used materials, and external hardware setups required to support the sensing units. Here we propose a silicon-polymer hybrid OoC device that encompasses transparency and biocompatibility of polymers at the sensing area, and has the inherently superior electrical characteristics and ability to house active electronics of silicon. This multi-modal device includes two sensing units. The first unit consists of a floating-gate field-effect transistor (FG-FET), which is used to monitor changes in pH in the sensing area. The threshold voltage of the FG-FET is regulated by a capacitively-coupled gate and by the changes in charge concentration in close proximity to the extension of the floating gate, which functions as the sensing electrode. The second unit uses the extension of the FG as microelectrode, in order to monitor the action potential of electrically active cells. The layout of the chip and its packaging are compatible with multi-electrode array measurement setups, which are commonly used in electrophysiology labs. The multi-functional sensing is demonstrated by monitoring the growth of induced pluripotent stem cell-derived cortical neurons. Our multi-modal sensor is a milestone in combined monitoring of different, physiologically-relevant parameters on the same device for future OoC platforms.

Left Ventricular Assist Device as a Destination Therapy: Current Situation and the Importance of Patient Selection.

Advanced heart failure is a growing problem for which the best treatment is cardiac transplantation. However, the shortage of donors' hearts made left ventricular assist devices as destination therapy (DT-LVAD) a highly recommended alternative: they improved mid-term prognosis as well as patients' quality of life. Current intracorporeal pumps with a centrifugal continuous flow evolved in the last few years. Since 2003, when first LVAD was approved for long-term support, smaller device sizes with better survival and hemocompatibility profile were reached. The most important difficulty lies in the moment of the implant. Recent indications range from INTERMACS class 2 to 4, with close monitoring in intermediate cases. Moreover, a large multiparametric study is needed for considering the candidacy: basal situation, with a special interest in frailty, comorbidities, including renal and hepatic dysfunction, and medical background, considering every prior cardiac condition, must be evaluated. In addition, some clinical risk scores can be helpful to measure the possibility of right heart failure or morbi-mortality. With this review, we sought to summarize all the device improvements, with their updated clinical results, as well as to focus on all the patient selection criteria.

A Full-Duplex Decode-and-Forward Relaying Approach Based on QAM Constellation Suitable for Small-Size Devices

The explosive growth of the Internet of Things (IoT) is putting higher requirements for the performance of co-time co-frequency full-duplex relaying (CCFD-R) due to small-size devices appearing in abundance. In this paper, we present a novel CCFD-R approach with very low complexity to deal with the issue above. Based on the orthogonality of its two components, a distributed usage mode of quadrature amplitude modulation (QAM) constellation is proposed to perform self-interference cancellation (SIC) without the complicated processing modules, as used widely in traditional full-duplex techniques. Instead of the conventional practice of assigning the entire QAM constellation to only one communication node, our scheme (termed as QAM-R) splits the constellation into two parts and further assigns them to different communication nodes, respectively. With the principle above, the mapping pattern and the frame format are carefully designed. Then, the corresponding signal model is established and the approximation of end-to-end bit error probability (BEP) is derived. Finally, numerical simulations validate the theoretical analysis and show that QAM-R can balance spectrum effectiveness and transmission reliability very well and, especially, performs even better in the low range of signal noise ratio (SNR) when adopting higher-order QAM constellations.

Sensors of Smart Devices in the Internet of Everything (IoE) Era

Smart device industry allows developers and designers to embed different sensors, processors, and memories in small-size electronic devices. Sensors are added to enhance the usability of these devices and improve the quality of experience through data collection and analysis. However, with the era of big data and machine learning, sensors’ data may be processed by different techniques to infer various hidden information. The extracted information may be beneficial to device users, developers, and designers to enhance the management, operation, and development of these devices. However, the extracted information may be used to compromise the security and the privacy of humans in the era of Internet of Everything (IoE). In this work, we attempt to review the process of inferring meaningful data from smart devices’ sensors, especially, smartphones. In addition, different useful machine learning applications based on smartphones’ sensors data are shown. Key Words: IOE-Internet of everything, near-field communication (NFC), Smartphones, interoperability, smart thermostat.

Recent Progress in Large‐Area Organic Solar Cells

Organic solar cells (OSCs) attract significant attention due to their great potential in flexible, lightweight, and low‐cost photovoltaic technology. Given the reformation of non‐fullerene acceptors, the certificated power conversion efficiency (PCE) of single‐junction OSCs has developed rapidly over 19% in the small device size (<1 cm2). However, the PCEs of large‐area OSCs are significantly lower than that of small‐area devices. Several essential issues in upscaling OSCs from small‐area to large‐area need to be overcome to bridge the efficiency gap, including coating techniques, material requirements, morphology optimization, flexible transparent electrodes development, and devices stability research. Herein, recent progress and challenges in materials and processing technologies of large‐area OSCs are summarized. Based on the analysis, strategies and opportunities are proposed to promote the development of large‐area efficient OSCs toward mass production.

A red-emitting micrometer scale LED with external quantum efficiency >8%

Significant efforts are being put into the development of efficient micrometer-scale light emitting diodes (LEDs) for future display technologies due to their marked benefits over existing displays. To date, however, the efficiency of microLED devices remains significantly lower than that of conventional broad-area devices. The deterioration in device performance with smaller device size has been linked to the plasma damage induced on mesa sidewalls during device fabrication. Here, we studied bottom-up red-emitting nanowire LEDs with different Mg doping levels in the p-GaN layer. The resulting sub-micron LED devices show a distinct improvement in efficiency with increasing Mg dopant incorporation. Through optimization of the doping, we measured an external quantum efficiency of ∼8.3% and a wall-plug efficiency of ∼4.6%, at a current density of ∼1 A/cm2, for a red-emitting sub-micrometer scale LED operating at >630 nm. This study highlights the importance of p-doping in microLEDs for attaining high efficiency performance in nanostructure-based devices.

Optimization design of feed array structure for space-borne synthetic multi-beam antenna

To reduce the difficulty of engineering realization as much as possible on the premise of ensuring the performance of the feed network, a new design method of the multi-feed composite multi-beam antenna feed array is proposed. In the design process, the method of longitudinal subdivision and layering is used to solve the processing problem of complex large-scale electrical and small-sized devices. Then the multi-objective and multi-variable differential evolution algorithm is used to optimize the distribution position of each mounting hole to realize the optimal interface layout. The method is used to optimize the design of a multi-beam antenna feed array and the product object is produced and tested. The test results show the effectiveness of the design method. This method can be used to guide designers to carry out actual engineering design, shorten the design cycle, and improve the design quality.

Advanced Molecular-Genetic Methods and Prospects for Their Application for the Indication and Identification of <i>Yersinia pestis</i> Strains

The review provides an analysis of the literature data on the use of various modern molecular-genetic methods for the indication and identification of Yersinia pestis strains with different properties and degree of virulence, which is caused by the diverse natural conditions in which they circulate. The methods are also considered from the perspective of their promising application at three levels (territorial, regional and federal) of the system for laboratory diagnosis of infectious diseases at the premises of Rospotrebnadzor organizations to solve the problem of maintaining the sanitary and epidemiological well-being of the country’s population. The main groups of methods considered are as follows: based on the analysis of the lengths of restriction fragments (ribo- and IS-typing, pulse gel electrophoresis); based on the analysis of specific fragments (DFR typing, VNTR typing); based on sequencing (MLST, CRISPR analysis, SNP analysis); PCR methods (including IPCR, SPA); isothermal amplification methods (LAMP, HDA, RPA, SEA, PCA, SHERLOCK); DNA-microarray; methods using aptamer technology; bio- and nano-sensors; DNA origami; methods based on neural networks. We can conclude that the rapid development of molecular diagnostics and genetics is aimed at increasing efficiency, multi-factorial approaches and simplifying the application of techniques with no need for expensive equipment and highly qualified personnel for analysis. At all levels of the system for laboratory diagnosis of infectious diseases at the Rospotrebnadzor organizations, it is possible to use methods based on PCR, isothermal amplification, SHERLOCK, biosensors, and small-sized sequencing devices. At the territorial level, at plague control stations, the use of immuno-PCR and SPA for the indication of Y. pestis is viable. At the regional level, introduction of the technologies based on the use of aptamers and DNA chips looks promising. For the federal level, the use of DNA origami methods and new technologies of whole genome sequencing is a prospect within the framework of advanced identification, molecular typing and sequencing of the genomes of plague agent strains.

Vibroacoustic Characteristics of a Specific Patterned Polymer with Graphene for an Electrostatic Speaker.

Graphene/polymer actuators were developed using bilayer graphene and various polymer substrates for use as transparent, flexible, and robust electrostatic speaker units. Additionally, a resonant frequency shift was induced using a polymer substrate on which various micropatterns were transferred to boost bass. The total sound pressure level (SPL) in the graphene/polymer actuator was measured by a sweep, and the frequency of the spectrum was confirmed to be one-third that of the octave band frequency. The change in the vibroacoustic characteristic with changes in Young's modulus and density was studied for the polymers of the same size and thickness. Particularly, the possibility of boosting bass was confirmed by inducing a resonant frequency shift and increasing the total SPL by adding micropatterns on a polymer substrate under the same conditions. The resonance frequency of 523 Hz and the SPL of 54 dBA in flat polymer film became 296 Hz and 69 dBA in a specific pattern, which produced a sound of >15 dB based on the same flat polymer. We expect that the design and information provided herein can provide the key parameters required to change the resonant frequency in small-size devices for the application of graphene/polymer thin-film actuators.

Simulation of a Single-Electron Device Based on Endohedral Fullerene (KI)@C180

The progress of modern electronics largely depends on the possible emergence of previously unknown materials in electronic technology. The search for and combination of new materials with extraordinary properties used for the production of new small-sized electronic devices and the improvement of the properties of existing materials due to improved technology for their manufacture and processing, in general, will determine the progress of highly promising electronics. In order to solve the problematic tasks of the miniaturization of electronic components with an increase in the level of connection of integrated circuits, new forms of electronic devices are being created using nanomaterials with controlled electrophysical characteristics. One of the unique properties of fullerene structures is that they can enclose one or several atoms inside their carbon framework. Such structures are usually called endohedral fullerenes. The electronic characteristics of endohedral fullerenes significantly depend on the properties of the encapsulated atom, which makes it possible to control them by choosing the encapsulated atom required by the property. Within the framework of the density functional theory in combination with the method of the nonequilibrium Green’s functions, the features of electron transport in fullerene nanojunctions were considered, which demonstrate “core–shell” nanoobjects, the “core” of which is an alkali halide crystal—KI—and the “shell” of which is an endohedral fullerene C180 located between the gold electrodes (in the nanogap). The values of the total energy and the stability diagram of a single-electron transistor based on endohedral fullerene (KI)@C180 were determined. The dependence of the total energy of fullerene molecules on the charge state is presented. The ranges of the Coulomb blockade, as well as their areas associated with the central Coulomb diamond were calculated.

Design of MEMS capacitive comb accelerometer with perforated proof mass for seismic applications

Micro Electro Mechanical System (MEMS) sensors are characterized by their small size, but their performances exceed that of their macro-scale counterparts. The small size of MEMS devices and their integration with microelectronics proves a major advantage. In this paper, a design of MEMS capacitive comb accelerometer for seismology application using COMSOL Multiphysics platform is presented. A seismometer (also known as a seismograph) is a device that is used to measure and record the behavior of seismic waves. With this data, the location and measure of earthquakes can be detected. This seismic device has a large frequency band, compared to traditional geophones and seismographs. In this paper, a study to measure amplitudes and frequencies of vibrations is presented, and the results are analyzed and compared for perforated mass and solid proof mass. The effect of the size of etch hole for perforation is also studied.The displacement sensitivity and capacitive sensitivity of accelerometer are found to be 1.188 × 10-9m/g and 1.093 × 10-21F, respectively.

The Role of Hand-Held Cardiac Ultrasound in Patients with COVID-19

The role of point-of-care ultrasound (POCUS) in patient management has been established in recent years as an important tool. It is increasingly used by multiple medical disciplines in numerous clinical settings, for different applications and diagnostic purposes and in the guidance of procedures. The introduction of small-sized and inexpensive hand-held ultrasound devices (HUDs) has addressed some of the POCUS-related challenges and has thus extended POCUS' applicability. HUD utilization is even more relevant in the COVID-19 setting given the operators' infection risk, excessive workload concerns and general equipment contamination. This review focuses on the available technology, usefulness, feasibility and clinical applications of HUD for echocardiogram assessment in patients with COVID-19.

Leveraging Augmented Intelligence of Things to Enhance Lifetime of UAV-Enabled Aerial Networks

Augmented intelligence is an innovative amplification of artificial intelligence that allows human experts to take over the autonomous decision of machines. It also facilitates human-intelligence-based decisions on the network edge using low-cost and small-sized devices. Augmented intelligence and the Internet of Things collectively create augmented intelligence of things. It logically and effortlessly interrelates human intelligence to articulate smart decisions. Unmanned aerial vehicles find various applications ranging from search operations during disasters to intruders identification; thus, they are suitable for aerial networks, where connections between base stations and servers are extinct. This article presents an approach to enhance the lifetime of unmanned-aerial-vehicles-enabled aerial networks via augmented intelligence. It first considers the available battery power to transform a large-size deep neural network into a lightweight. We next present a knowledge-distillation-based approach, which reduces training time and enhances accuracy. Finally, we evaluate the approach on the existing dataset.

Differential method for determining the specific absorption rate coefficient of electromagnetic energy for a liquid phantom

The wide use of small-sized wearable electronic devices in various practical human activities makes it relevant to measure the proportion of electromagnetic energy absorbed by the human body. One of the most important parameters that determines it is the specific absorption rate. In this article we propose a method for determining this coefficient for a liquid phantom, with the use of computer simulation and experimental measurement of the microstrip patch antenna parameters.The antenna is located on an elliptical cylinder and operates in the medical body area network. The method is based on measuring the rise in temperature of the liquid phantom exposed to electromagnetic waves generated by a microstrip antenna over a given time. Homogeneous liquid phantom was created by changing the percentage of salt and sugar in 250 g of water, skin phantom – by changing the percentage of water in 200 g of glycerol. The proposed specific absorption rate measurement method eliminates the need to purchase an expensive set of dielectric probes, which demonstrates its cost-effectiveness. The obtained results of experimental measurements are in good agreement with the results of the performed computer simulation.

Stochastic analysis of small-scale beams with internal and external damping

Random flexural vibrations of small-scale Bernoulli–Euler beams with internal and external damping are investigated in the paper. Such a kind of problem occurs in design and optimization of structural components of smart miniaturized electromechanical systems. Internal damping is related to the viscoelastic stress–strain law describing the beam time-dependent behavior while the external damping represents the interaction between the structure and the surrounding viscous environment. In the proposed formulation, Boltzmann superposition integral and fractional-order viscoelasticity are exploited to capture the above mentioned non-conventional phenomena. Size effects caused by long range interactions arising at small-scale are also taken into account and modeled by means of an integral nonlocal formulation based on the stress-driven approach. Moreover, in order to reproduce stochastic vibrations of small-size devices, such as resonators and sensors, the external loading are modeled by taking into account their random nature. The relevant dynamic problem is thus described by a fractional-order stochastic partial differential equation in space and time equipped with standard and non-classical boundary conditions. A proper differential eigenanalysis for the nonlocal viscoelastic bending problem is performed to find the modal shapes and closed-form expressions of power spectral density and stationary variance of displacements are provided. The proposed methodology, accounting for size-effects, hereditariness behaviors, viscous properties of surrounding environment and randomness of external loadings, is suitable to model and capture the effective behavior of miniaturized devices. The presented theoretical findings and numerical outcomes show the influence of size-effects and viscoelastic parameters on the structural response.