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Several miniaturized viscometers, or microviscometers, have been developed exploiting numerous rapid prototyping techniques. Among them, paper microstrips, famously known as microfluidic paper-based analytical devices ( $\mu $ PADs), have become popular due to their cost-efficacy, simple fabrication, fast response, and easily disposable. Many fabrication methods are existing to develop paper microstrips. Herein, an alternative fabrication method is proposed where fused deposition modeling (FDM)-based 3-D printer (3DP) has been employed using polycaprolactone (PCL) filament. F, image processing has been utilized to measure viscosity in such microfluidic domain. Viscosity was calculated by measuring the time taken by the fluid to cover a fixed length between two spots in the microchannel based on the programed and color-coded regions-of-interest. The image processing program was developed considering the change in the gray scale in the virtual region of interests (ROIs) in the microchannel during the fluid flow in the paper microstrips. A 3-D printed handheld platform, containing raspberry pi with on-board camera and display, was developed to execute the image processing and automate the entire work flow. In the proposed device, the accuracy was measured to be >92%.

We demonstrate edge electron emission from flexible free-standing graphene paper (GP). The turn-on field is measured at 2.2 V/ $\mu{\rm m}$ , and the maximum emission current density at 3 ${\rm A}/{\rm cm}^{2}$ . The field emission properties of GP can be optimized by adjusting the thickness and annealing temperature. Because it is flexible, it can be shaped into different forms to meet the requirements of specific applications. The electron beam shape can range from a sheet electron beam to a cylindrical (hollow) electron beam.

Oxide-based thin-film transistors (TFTs) with a lateral in-plane electrode are self-assembled on paper substrates, and the electrical modulation effect of the in-plane electrode is investigated. A SiO2-based solid-electrolyte film with high specific capacitance is used as the gate dielectric, and the operation voltage is reduced to less than 2.0 V. The threshold voltage (Vth) of such paper TFTs is tuned from -0.98 to 0.94 V by different voltage biases on the in-plane electrode. The threshold voltage shift (ΔVth) can be described by ΔVth = -(CG2/CG1)VG2, where CG2 and CG1 are the in-plane electrode and bottom-gate specific capacitance values. High electrical performance with a current on/off ratio of 6 ×105 ~ 106, a subthreshold swing of 0.14 ~ 0.19 V/dec, and a mobility of 8.64 ~ 9.45 cm2/V·s is obtained at different in-plane electrode voltage biases. Such low-voltage paper TFTs are promising for low-cost and portable electronics.

The electrophoretic display (EPD) is the main solution to electronic papers, but most of them can display the image or text in black and white particles only. The users may prefer the EPD showing multiple colors rather than the black/white content only. In this paper, we introduce the driving system for a color EPD, which is composed of three kinds of particles. The system aims at optimizing the visual quality based on a new driving waveform by equipping with an optimization method for color and tone reproduction. The experimental result shows that the proposed EPD driving system can display three-color pictures with promising visual quality.

This paper presents a parallel plate-type field emission device of potassium hydroxide-doped electrochemically reduced graphene oxide (GO) manufactured using highly oriented pyrolytic graphite through electrochemical exfoliation. The material properties of the GO were tested through Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The optimal electron emission characteristics of the device were as follows: turn-on field = 2.03 V/ $\mu \text{m}$ , field emission current $= \,\, 16.4~\mu \text{A}$ , and field emission enhancement factor = 8377. At an emission peak wavelength of 563.7 nm, the optimal device had a light flux of 4.21 lumens and an illumination of 140.3 lux. These properties can be utilized in various optoelectronic devices, such as nanoelectronics devices, sensors, electrochemical systems, and energy storage devices.

In this paper, a fully controlled photocatalytic reduction of graphene oxide (GO) sheets is presented in which electrical bias is applied in combination with UV illumination. It is proved that this controllability allows higher conductivities and lower UV illumination times for the achieved reduced graphene oxide (rGO) sheets, which are not allowed without gate voltage. We attribute the observed enhancement mechanism in photocatalytic reduction to electron accumulation at the ZnO/GO interface and decrement of recombination of photogenerated carriers. Then, we applied ZnO nanowires to reduce the GO sheets locally and realize rGO ribbons. The optoelectric response of the fabricated photodetector based on the realized rGO ribbon shows that by controlling the photocatalytic reduction, we can achieve a tunable/selective photodetector ( $\lambda _{\mathrm {incident}} = 520$ , 595, and 633 nm have been investigated). These functionalities allow tuning the output sensitivity of the device in response to different incident wavelengths along the fabrication process or even after the fabrication process. We believe that the presented approach introduces a new generation of tunable devices suitable for different application fields, including optoelectronics.

A single atomic layer of graphene, integrated onto an undoped bulk substrate in a back-gated transistor configuration, demonstrates surprising strong photoconduction, and yet, the physical origin of the photoresponse is not fully understood. Here, we use a detailed computational model to demonstrate that the photoconductivity arises from the electrostatic doping of graphene, induced by the surface accumulation of photogenerated carriers at the graphene/substrate interface. The accumulated charge density depends strongly on the rate of charge transfer between the substrate and the graphene; the suppression of the transfer rate below that of carrier’s thermal velocity is an essential prerequisite for a substantial photoinduced doping in the graphene channel under this mechanism. The contact-to-graphene coupling (defined by the ratio of graphene–metal contact capacitance to graphene’s quantum capacitance) determines the magnitude of photoinduced doping in graphene at the source/drain contacts. High-performance graphene phototransistors would, therefore, require careful engineering of the graphene–substrate interface and optimization of graphene–metal contacts.

We present a computational study on hybrid nanomaterial-insulator-silicon solar cells where single-walled carbon nanotube or graphene forms the emitter as well as top conducting electrode on n-type crystalline silicon having a thin interfacial tunnel oxide. The effects of nanomaterial doping and tunnel oxide thickness on cell characteristics are modeled. Similar to bulk emitters, cell efficiency could be increased by chemical doping (p-type) of the nanomaterial. Unlike bulk, nanomaterial could get electrostatically doped (n-type) due to its low quantum capacitance, by the surface charge density in silicon. For chemically undoped graphene on lightly ( $10^{{16}}$ /cm $^{{3}}$ ) doped silicon, efficiency loss due to the electrostatic doping effect is $\sim 11$ %. A moderate p-type chemical doping (0.2 eV shift in Fermi level) of graphene reduces the aforementioned loss to $\sim 2$ %. The electrostatic doping effect in carbon nanotube-based cells is relatively small and independent to nanotube’s chemical doping. For tunnel oxide thickness $\ge 2$ nm, photogenerated carrier accumulation at silicon/oxide interface considerably enhances the electrostatic doping effect. The effect of tunnel oxide thickness variation on fill factor and open circuit voltage is shown to be qualitatively similar to standard bulk metal–insulator–silicon solar cells. Our model predicts an optimal oxide thickness of $\sim 1$ nm which confirms the experimental reports.

This paper investigates the plasma-spraying technique as applied to oxide cathodes compared with the conventional coating method. In the conventional oxide cathode manufacturing process, a carbonate powder layer BaSrCa(CO3) is either painted or sprayed onto the nickel-base material at room temperature after the carbonate powder has been mixed with a nitrocellulose binder to provide adhesion to the nickel surface. However, the by-products deposited due to the coating of the oxide cathode and the decomposing process, combined with the relatively weak adhesion resulting from this coating method, undermine the performance of the oxide cathode. Plasma spraying can produce a high-quality coating by applying a relatively inert medium using a high-temperature high-particle velocity process. Impacts on the performance of the plasma-sprayed oxide cathode, as compared with a conventionally coated oxide cathode, are presented. The experimental results show that the pulsed-current emission density of a plasma-sprayed oxide cathode is nearly twice that of the conventionally coated oxide cathode, whereas the evaporation rate of the plasma-sprayed oxide cathode is only 10% as much as the conventionally coated oxide cathode.

An electrophoretic display (EPD) cell with a triple-layered microcavity structure was fabricated using a convenient dry film resist. The inherent structural advantage arising from the function of the middle channel layer as a background colored state enabled the EPD to operate with two different-colored states by using a single type of electronic-ink particles, thereby eliminating the possible agglomeration of oppositely charged ink particles and supporting the potential application of the proposed structure to color the electronic paper. The preliminary operation of this new EPD structure was demonstrated as white and blue display states on a rigid glass exhibiting a contrast ratio of 1.5 : 1 with saturation voltages of + 30 and -30 V, respectively. Successful demonstrations on both the indium-tin-oxide-patterned glass and flexible polyethylene substrates are also provided.

A high-resolution active-matrix microencapsulated electrophoretic display (EPD) driven by polycrystalline-silicon thin-film transistors (poly-Si TFTs) with integrated drivers has been developed for the first feasibility study of electronic paper. The poly-Si TFTs were fabricated with a low temperature process below 425/spl deg/C. Microencapsulated electrophoretic material was coated on the TFT backplane, which was driven at 18 V. The resolution of the display is quarter VGA (video graphics array), and pixel pitch is 131 ppi (pixels per inch). As a result, this display offers a wide viewing angle, high contrast ratio and nonvolatilization of data. In addition, four-level grayscale images were also achieved by using an area ratio grayscale (ARG) driving method.

We present an approach to mass produce high-quality graphene on insulator substrate. Ni dots with single or few grains were achieved by annealing. Electron backscattered diffraction indicated that almost all of the Ni dots had (111) surface that is parallel to the substrate. Single-layer graphene with good crystalline quality has been grown on Ni dots. The patterned graphene films were transferred to insulating substrates by wafer bonding and etch back technique, which resulted in zero misalignment, low contamination, and high yield (>90%). Graphene-based field-effect transistors with self-aligned gate were fabricated with this method, which demonstrate the potential of this method as a candidate for mass production of graphene transistors.

We propose a new kind of cathode-ray tube, namely, the thermal-transmission cathode-ray tube (TTCRT). In the TTCRT the electron beam focused to a small spot is called upon to heat in sequence small elements of a matrix that constitutes the faceplate of the tube. A heat-sensitive or thermal paper passed across the screen and maintained in contact with it, and outside the tube, will record characters and dot patterns generated through suitable two-dimensional deflection of the electron beam. We give a description of the main parameters regulating the performance of the TTCRT.

We report in this paper the design and fabrication of single-chip alternating current-LEDs (AC-LEDs) by monolithically integrating, for the first time, high-breakdown Schottky barrier diodes (SBDs) and micro-LED arrays using III-nitride LED epi-wafers of standard specs for volume production. A technique of cyclic mixed-etching has been introduced to restore the surface of inductively coupled-plasma (ICP) etching processed gallium nitride to device quality for fabricating high-breakdown Schottky junctions. Proof-of-concept single-chip AC-LED devices and a prototype driver-free white AC-LED lamp were demonstrated, showing high-efficiency LED emission, high chip area utilization efficiency, low power loss of the on-chip SBD bridge rectifier, and good luminous efficacy of the prototype AC-LED lamp. This paper paves the way toward mass-producing reliable and low-cost driver-free AC-LED lamps for solid-state lighting with existing LED manufacturing infrastructures.

This paper reports an industry standard monolithic 555-timer circuit designed and fabricated in the in-house silicon carbide (SiC) low-voltage bipolar technology. This paper demonstrates the 555-timer integrated circuits (ICs) characterization in both astable and monostable modes of operation, with a supply voltage of 15 V over the wide temperature range of 25 °C–500 °C. Nonmonotonic temperature dependence was observed for the 555-timer IC frequency, rise time, fall-time, and power dissipation.

Quantum dot (QD) white light-emitting diodes (LEDs) are promising devices in illumination and display applications, and the low thermal stability of QDs is one of the biggest problems limiting their practical use. In this paper, we proposed a metal-based inverted packaging (MIP) structure to enhance the thermal performance and stability of QD white LEDs. The results indicate that the thermal power of LED chips can greatly increase the surface temperature of QD white LEDs, especially that of the color-converted layer and the base. Therefore, the LED chip was separated from the QD layer and isolated with low thermal conductivity layers of air and glass using the MIP structure. This successfully reduces the base temperature and constrains the thermal power of the LED chip on the upper phosphor layer, thus enhancing the thermal performance for the QD layer. Consequently, MIP-QD white LEDs have a small deviation of 57.3 K in their correlated color temperature (CCT) and a deviation of 0.29 in their color rendering index (CRI) at injection power values in a wide range of 0.08–1.3 W, with mean values of 4382 K and 90.3, respectively. Moreover, these devices have negligible reduction in their electroluminescence intensity, and CCT and CRI values after aging for 10 h under severe conditions at an injection power of 0.9 W. Consequently, this paper can provide a general guide to enhance the thermal performance and stability of QD white LEDs by separating the thermal power of the LED chip from the QD layer.

Photodetectors (PDs) based on organic–inorganic hybrid materials such as graphene and perovskites have recently emerged at the forefront of the research in optoelectronic devices. Despite the remarkable progress in the performance of optoelectronic devices based on hybrid materials, some aspects such as stability have so far not been thoroughly addressed. This paper serves to demonstrate a fully inkjet-printed PD fabricated by hybrid perovskite (CH3NH3PbClx-3I3) layer between the two graphene electrodes as graphene/perovskite/graphene (GPG) heterostructure. The fully inkjet-printed GPG PD is found to be effective for the visible light region, which can be attributed by the high uniformity and low defects of the printed materials. Thus, the GPG PD achieves a high responsivity of 0.53 A/W. Fully inkjet-printed hybrid perovskite PD demonstrated in this paper unveils the facile, potentially large-scale and cost-effective methods for fabrication of hybrid perovskites-based optoelectronic devices, including PDs and solar cells.

This paper clarifies the correct transmission mechanism, misattributed in the previous research, of a hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) device. Complete drain current–gate voltage ( ${I}_{\text {D}}$ – ${V}_{\text {G}}$ ) transfer characteristics including the forward and backward gate sweeps (gate voltage carried out in the OFF-state $\to $ on-state and the ON-state $\to $ OFF-state) are performed, and the physics models of an energy-band schematic are clearly explained. This paper reveals that the ${I}_{\text {D}}$ – ${V}_{\text {G}}$ curve stretch-out behavior of the subthreshold region is due to the leakage of the Poole–Frenkel region. At the Poole–Frenkel regions, electrons transfer to the drain terminal, and holes remain in the valance band of the a-Si:H bulk. The remaining holes represent the positive voltage and cause the electron barrier height lowering. This causes an increase in subthreshold current of the subthreshold region. Finally, three experiments are performed to prove the correctness of these models, and the a-Si TFTs device improvement methods will be proposed to enhance the stability and performance of product of the a-Si TFTs.

In this paper, we propose a novel reconfigurable ferroelectric FET (R-FEFET), which can reconfigure its operation between volatile and nonvolatile modes during run-time by dynamically modulating its hysteresis. The R-FEFET comprises of two gates with ferroelectric (FE) in both the gate stacks. One of these terminals serves as a regular gate, while the other is used as a control to introduce reconfigurability. Employing Landau–Khalatnikov equation-based FEFET model, we extensively analyze the device characteristics in both FinFET and planar technologies. We show that by changing the control voltage between 0 and 1 V, the hysteresis width (HW) can be modulated between 1.1 and 0.3 V. In addition, we show the device characteristics and advantages that R-FEFETs possess to overcome the drawbacks encountered with gate leakage in standard FEFETs. The hold margins in the nonvolatile mode of R-FEFETs increase by ~ $10\times $ with respect to standard FEFETs, and the drive current strengths in the volatile mode show 13% improvements when compared to standard FETs. Using the proposed R-FEFETs, we examine a low-power nonvolatile memory design in Part II of this paper.

International audience; Abstract:This paper details an extraction procedure to fully model the transient self-heating of transistors from a GaN HEMT technology. Frequency-resolved gate resistance thermometry (f-GRT) is used to extract the thermal impedance of HEMTs with various gate widths. A fully scalable analytical model is developed from the experimental results. In the second stage, transient thermoreflectance imaging (TTI) is used to bring deeper insights into the HEMTs' temperature distribution by individually extracting the transient self-heating of each finger. TTI results are further used to successfully validate the f-GRT results and the modeling of the thermal impedance. Overall, f-GRT is demonstrated to be a fast and robust method for characterizing the transient thermal characteristics of a GaN HEMT. For the first time to the authors' knowledge, a scalable model of the thermal impedance is extracted fully from experimental results.

In the domain of printed electronics (PE), field-effect transistors (FETs) with an oxide semiconductor channel are very promising. In particular, the use of high gate-capacitance of the composite solid polymer electrolytes (CSPEs) as a gate-insulator ensures extremely low voltage requirements. Besides high gate capacitance, such CSPEs are proven to be easily printable, stable in air over wide temperature ranges, and possess high ion conductivity. These CSPEs can be sensitive to moisture, especially for high surface-to-volume ratio printed thin films. In this paper, we provide a comprehensive experimental study on the effect of humidity on CSPE-gated single transistors. At the circuit level, the performance of ring oscillators (ROs) has been compared for various humidity conditions. The experimental results of the electrolyte-gated FETs (EGFETs) demonstrate rather comparable currents between 30%–90% humidity levels. However, the shifted transistor parameters lead to a significant performance change of the RO frequency behavior. The study in this paper shows the need of an impermeable encapsulation for the CSPE-gated FETs to ensure identical performance at all humidity conditions.

In this paper, a novel vertical phototransistor was reported and compared with planar phototransistors for the first time. As compared with the planar phototransistors, the vertical ones exhibited much better photoelectric performance, which is attributed to an ultrashort photo-generated holes transfer distance and a stronger excitons dissociating electrical field due to their ultrashort channel length (tens of nanometers). Moreover, in order to examine the transport and trapping of different carrier charges separately, the impact of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) dopant on the performance of planar and vertical phototransistors was investigated. The vertical devices exhibited an ultrahigh responsivity (~6600 A/W) as well as an excellent detectivity ( $\sim 7\times 10^{15}~\text{Jones}$ ) and a fast photoresponse (rise time of 0.28 s), whereas slight changes were observed in the planar ones with doping of PCBM. The high performance of the blend vertical phototransistors is due to the trapping of the photo-generated electrons with PCBM and the effective transport of holes due to the ultrashort channel length. This paper provided a promising pathway for low-cost, high-performance phototransistors.

The instability of amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) under ultraviolet (UV) light was thoroughly investigated in this paper. Unlike in a darkened state, an off-state leakage current can be found in the dual-sweep I–V transfer curve of a-IGZO TFTs under UV light illumination. Furthermore, despite the same UV light condition, the forward sweep and reverse sweep show different I–V curves, representing two different physical mechanisms. First, the subthreshold swing degradation and threshold voltage shift to the negative direction in the forward sweep are due to the total channel barrier lowering and can be confirmed by changing the light exposure region. Second, in the reverse sweep, the suggested back-channel leakage current can be controlled by dual-gate TFTs. UV light exposure of the metal–insulator–semiconductor–metal structure verifies that the off-state leakage current passes through the back channel in a reverse sweep. Finally, the physical mechanism links between forward and reverse sweeps have comprehensive interpretation in this paper.

Ferroelectric and negative-capacitance field-effect transistors (FeFETs and NCFETs) have recently garnered great attention as devices for applications in memory and low-power logic, respectively. As these technologies are pursued, it is critical to have a variety of measurement approaches, including methods familiar to the electron-device and microwave communities that can aid in fully understanding the behavior of ferroelectrics in FeFETs and NCFETs. In this paper, we propose and show the viability of using frequency-domain electrical measurement techniques employing the well-known microwave S-parameters, and their large-signal generalization and X-parameters. Our methods provide the means to trace the intrinsic polarization versus electric-field curve of the ferroelectric, i.e., with the parasitics de-embedded, thereby showing the innate ferroelectric response, which cannot be done using conventional techniques. These methods also enable extraction of all the parameters of the Landau–Khalatnikov equation, which is commonly used to model ferroelectric behavior in FeFETs and NCFETs. This paper hence takes a useful step toward methods familiar to the electron-device community that can help to better understand and optimize FeFET and NCFET technologies.

In this paper, an inner ultrathin oxide metal–oxide–semiconductor (MOS) capacitor is fabricated with another outer MOS-gate ring as a coupling controller. Capacitance–voltage characteristics of inner MOS capacitor show that the excess minority carriers supplied from the outer MOS-gate ring can efficiently change the inner capacitance ( ${C} _{\text {inner}}$ ). It is observed that outer MOS-gate ring under the conditions at floating and at ground has quite different coupling effects on ${C} _{\text {inner}}$ when the inner MOS is biased at 1 V. Comparing to ${V} _{\text {outer}} = \text {floating}$ , ${C} _{\text {inner}}$ reduces significantly when ${V} _{\text {outer}} = {0}$ V at 1k Hz. The transient behavior of ${C} _{\text {inner}}$ as ${V} _{\text {outer}}$ changes from 0 V to floating is long enough to read, and the difference of two capacitance values can be regarded as two states. As a result, a two capacitance states operation is proposed for possible memory application. Based on the experimental results, the possible memory cell configuration is designed. Comparing to the present emerging memories, since the two states in this paper are in conditions of floating and 0 V, ultralow power is consumed, which is believed a promising concept for future memory application.

In this paper, an analytical model has been developed to observe the recombination losses involved in a tunnel oxide passivated contact solar cell with a carrier-selective layer constituting polycrystalline silicon (poly-Si). The main focus of this paper is to observe the contribution of each component of recombination current density and its effect on open-circuit voltage, Voc. The effect of emitter saturation current density (Joe), surface recombination velocity, substrate thickness, and doping density of carrier-selective layer on Voc has been presented. The analysis indicates that Voc = 766 mV can be achieved for Joe = 2 fA/cm2, and a doping density of poly-Si > 1021cm−3 in a c-Si/SiO2/poly-Si contact for a 50- $\mu \text{m}$ -thick substrate in case of ideal surface passivation. For identical conditions, Voc attains a lower value of 750mV for a 180- $\mu \text{m}$ -thick substrate. The dependence of Voc on bandgap of tunnel layers has also been observed by considering other materials like Si3N4 and SiC. These results from the analyticalmodel have been compared with results froma simulation using automat FOR simulation of HETerostructures v2.5 and have been found to be in good agreement with each other.

In this paper, we have developed a physics-based analytical model for the electrical characteristics of passivated silicon carrier-selective contact (CSC) solar cells and validated it with numerical simulations. The model comprises analytical solutions of: 1) the Poisson equation, accurately capturing the level of inversion and accumulation at the crystalline silicon (c-Si) layer interfaces, and 2) the recombination current capturing the various recombination mechanisms at work in the solar cell. The calculations establish that CSC solar cells have the potential to achieve an efficiency greater than 26% even when both c-Si interfaces have realistic SRV values of 100 cm/s. The model helps illustrate the physics underlying the performance of CSC solar cells for variation in key device parameters such as surface recombination velocities, bulk lifetime, contact layer doping, and amorphous silicon (a-Si) thickness amongst others. By circumventing the need for resource-intensive numerical simulations, the analytical model described in this paper can assist in the design and development of high-performance CSC solar cells.

Inverter delay is often evaluated as $\textit {CV}_{\text {dd}}/{I}_{\text {eff}}$ , where ${C}$ is the load capacitance, ${V}_{\text {dd}}$ is the supply voltage, and ${I}_{\text {eff}}$ is the effective drive current derived by approximating the inverter switching trajectory with a linear model. The ${I}_{\text {eff}}$ model utilizes high and low drain currents conventionally measured in wafer acceptance tests and does not require extraction of any parameters. Ease of use combined with reasonable accuracy (~15%) is the main reason for wide application of $\textit {CV}_{\text {dd}}/{I}_{\text {eff}}$ delay metrics. However, $\textit {CV}_{\text {dd}}/{I}_{\text {eff}}$ expression produces large errors when applied to another two important basic circuits: NAND and NOR. This is because NAND and NOR circuits contain transistor series connections not accounted for in the inverter model. In this paper, an analytical solution for the transistor series connection influence on the discharge/charge operation in NAND/NOR circuits is provided. The model for NAND/NOR effective drive current (denoted as ${I}_{\text {stack}}$ ) developed in this paper maintains simplicity of the original ${I}_{\text {eff}}$ expression. It requires only one additional measurement of the linear current. Model accuracy was assessed by comparing to extensive SPICE delay simulations of NAND and NOR circuits designed using state-of-the-art MOS technologies. Comparison results show that $\textit {CV}_{\text {dd}}/{I}_{\text {stack}}$ equation provides ~15% accuracy for NAND/NOR circuits in line with $\textit {CV}_{\text {dd}}/{I}_{\text {eff}}$ accuracy for inverter. In an era of emphasis on low-power design, the developed model presents convenient means of exploring design space when optimizing circuit supply voltage for low-power operation.

In this paper, we propose a novel static random access memory (SRAM) unit cell design and its array structure consisting of single-gated feedback field-effect transistors (FBFETs). To verify the SRAM characteristics, the basic memory operations and write disturbances of the unit cell are investigated through the mixed-mode technology computer-aided design simulations. The unit cell exhibits the superior SRAM characteristics including a write speed of 0.6 ns, a fast read-out speed of ~0.1 ns, and a retention time of 3600 s. Furthermore, the unit cell design exhibits advantages in density, with a small cell area of 8F2, and in the power consumption; the standby power consumption is 0.24 nW/bit for holding “1” and negligible for holding “0.” Moreover, our SRAM array shows reliable ${3} \times {3}$ array operations without any disturbances. This paper demonstrates the promising potential of the FBFET SRAM for high-performance, high-density, and low-power memory applications.

This paper proposes amorphous indium–gallium–zinc oxide thin-film transistors (TFTs) four-transistor-two-capacitor (4T2C) pixel circuit in combination with a top-anode organic light-emitting diode (OLED) for the use in 8K4K active-matrix organic light-emitting diode displays (AM-OLEDs). The proposed pixel circuit compensates for driving TFTs threshold voltage ( ${V} _{\textsf {TH}}$ ) shifts and mobility variations, ${V} _{\textsf {DD}}$ current–resistance ( ${I}$ – ${R}$ ) drops, and ${V} _{\textsf {SS}}~{I}$ – ${R}$ -induced rises. Both the positive and negative ${V} _{\textsf {TH}}$ of the driving TFT can be sensed by the proposed circuit. In this paper, we analyze the impact of the driving TFT compensation time for low gray levels. The current error rates are calculated when TFT mobility variations are considered. The proposed pixel circuit allows an increase in the compensation time to reduce the impact of driving TFT ${V} _{\textsf {TH}}$ and mobility variations on the performance of 4T2C pixel circuit. Conventional two-transistor-one-capacitor, five-transistor-two-capacitor, and proposed 4T2C pixel circuits are simulated and compared in this paper. The proposed pixel 4T2C circuit reduces the current error rates to below 5.79% when the ${V} _{\textsf {TH}}$ shifts of ±2 V, mobility variations of ±10%, ${V} _{\textsf {DD}}~{I}$ – ${R}$ drops of 1 V, and ${V} _{\textsf {SS}}~{I}$ – ${R}$ rises of 1 V are all considered. We show that the proposed 4T2C pixel circuit is suitable for 8K4K AM-OLEDs.

In this paper, the threshold voltage characteristics of silicon nanowire metal–oxide–semiconductor field-effect transistor (MOSFET) with a double-layer gate structure are presented. This type of device is considered to be the most promising application of nanodevice in ultralarge-scale integration, due to several advantages such as similar operation principle as the junctionless nanowire transistor, the screening effect of the upper gate (UG) to shield the lower gate MOSFETs from external electromagnetic disturbance, the tradeoff between the short channel and the thick-gate oxide layer, and the compatible fabrication process with the conventional MOS technology. In this paper, the relations of threshold voltage versus the gate length, the UG bias, the substrate bias, the drain bias, and the temperature are measured and analyzed. Moreover, the penetration effect of the UG electric field is proposed to interpret the short-channel characteristics of the device, and a piecewise curve model is presented to reveal the underlying physics of the relation of the threshold voltage versus the drain bias. The double-layer gate structure technology enables the design of many devices, such as small-signal analog circuit units, single-electron devices, and quantum bit cells.

We demonstrate, for the first time, resistive RAM (RRAM) arrays where each cell can store 3 bits. Such full array-level demonstration is possible through special techniques (e.g., that exploit RRAM-specific characteristics of variations in cell resistances), presented in this paper, which efficiently allocate resistance range corresponding to each bit combination (required for proper write operation) while maintaining appropriate sensing margin (required for proper read operation). Our techniques are not restricted to 3 bits-per-cell only (and, in this paper, we demonstrate 2 bits-per-cell at the array level as well). Our measured results are based on multiple 4 Kbit arrays of 1T1R HfOx-based RRAM integrated in the back end of the line of 130-nm silicon CMOS technology. We achieve 3 bits-per-cell (2 bits-per-cell) RRAM with 11 (3) programing iterations on average.

The effect of back-bombardment (BB) electrons is considered one of the main obstacles for extensive use of thermionic RF guns (T-RF). The 10 hexaboride materials named (Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Eu, and Gd) B6 are investigated in this paper to survey the effect of the cathode material on reducing BB electrons and compare them with LaB6 (which is widely used as a thermionic cathode). A numerical model was used to conduct this paper. Besides the numerical calculations, an experiment has been performed to determine the work functions of CeB6 and LaB6. The results from the numerical calculations revealed that (Ba, Ca, and Nd) B6 are less affected by BB electrons: 42%, 50%, and 59%, respectively, compared with LaB6, for low beam current applications. In contrast, for high beam current duties, (Nd, Ce, and Sm) B6 have minimum influence by BB electrons compared with other hexaborides. The study concluded that BB electrons are strongly affected by the properties of the cathode material, especially thermionic emission and material density. Moreover, the study suggests that it is worthwhile to prepare BaB6, CaB6, NdB6, and SmB6 as cathode materials, then to subject them to a real experimental test using T-RF gun to compare their performance and BB effect against LaB6.

In this paper, for the first time, we demonstrate the improvement in power capability and safe operating area of silicon-on-insulator laterally double-diffused MOS (SOI-LDMOS) transistors for power amplifier applications by the introduction of a partial n+ buried layer (PNBL). The power capability of a transistor can be evaluated by ${P}_{\text {max}}/A$ , which is the maximum power per unit area that can be delivered by the transistor and is an important parameter for power amplifiers. ${P}_{\text {max}}$ is dependent on the snapback voltage ( ${V}_{\text {sb,QS}}$ ), OFF-state breakdown voltage ( ${V}_{\text {bd}, \mathrm{\scriptscriptstyle OFF}}$ ), and maximum current ( ${I}_{\text {max}}$ ) in the quasi-saturation regime of an LDMOS transistor. Increase of ${P}_{\text {max}}/A$ by the introduction of a PNBL in the SOI-LDMOS transistors is reported in this paper. The effects of variation of the length, thickness, and doping concentration of the PNBL on ${V}_{\text {sb,QS}}$ and ${P}_{\text {max}}/A$ are analyzed in detail. It is shown that by optimizing the doping and length of the PNBL layer, the maximum power output from the transistor can be made significantly higher than that of a conventional device without PNBL. A procedure to design the optimized structure is also presented.

The application of capacitive deep trench isolation (CDTI) as a shared vertical transfer gate (VTG) in a back-side-illuminated CMOS image sensor pixel is investigated using 3-D device-level simulations. The parasitic capacitance existence between CDTI and deeply buried pinned photodiode (BPD), and also between CDTI and floating diffusion (FD) region, makes the charge transfer process more difficult. In order to design a lag-free pixel and obtain complete charge transfer from BPD to FD, various considerations regarding the device-level design should be taken into account which is discussed in this paper. A CDTI neighboring two pixels can be functionalized as a shared VTG. Using CDTI as shared VTG facilitates pixel miniaturization and can result in more circuit integration at the pixel surface. This paper proposes a ${2}\,\,\mu \text{m} \times {2}\,\,\mu \text{m}$ pixel with CDTI as shared VTG, an equilibrium full-well capacity of 4605 e−, and a complete charge transfer from BPD to FD.

© 2018 IEEE. In 2-D van der Waals heterostructures, interactions between atomic layers dramatically change the vibrational properties of the hybrid system and demonstrate several interesting phenomena that are absent in individual materials. In this paper, we have investigated the vibrational properties of the heterostructure between transition metal dichalcogenide (TMD) and hexagonal boron nitride (hBN) on gold film at low- and high-frequency ranges by Raman spectroscopy. Nineteen Raman modes have been observed from the sample, including a new interlayer coupling mode at 28.8 cm-1. Compared to reported experimental results of tungsten disulfide (WS2) on SiO2/Si substrates, the Raman spectrum for WS2 on hBN/Au emerges a blue shift of about 8 cm-1. Furthermore, a remarkable enhancement of Raman intensity can be obtained when tuning hBN thickness in the heterostructure. Through systematic first-principles calculations, numerical simulations, and analytical calculations, we find that the 28.8 cm-1 mode originates from the shearing motion between monolayer TMD and hBN layers. In addition, the gold substrate and hBN layers form an optical cavity and the cavity interference effects enhance the obtained Raman intensity. This paper demonstrates the novel vibrational modes of 2-D van der Waals heterostructure as an effective tool to characterize a variety of such heterostructures and reveals a new method to enhance the Raman response of 2-D materials.

This paper analyzes the performance of mosaic nonimaging passive infrared (PIR) sensors fabricated by the CMOS–SOI–MEMS technology. The elementary sensor, forming a subpixel, is a thermally isolated nanomachined CMOS transistor, dubbed TMOS, operating at subthreshold. The mosaic uncooled PIR sensors are composed of several TMOS subpixels, which are electrically connected, either in parallel or in series as well as a combination of both options. These mosaic sensors, which are manufactured by nanofabrication methods, exhibit enhanced performance and robust manufacturing on wafer level. The overall figures of merit of these sensors, which are modeled in this paper, indicate why they are most suitable for consumer electronics, including smart homes, wearables, Internet of Things as well as mobile applications.

This paper demonstrates a high-performance black phosphorus nanoribbons field-effect transistor (BPNR-FET) and systematically investigates methods for enhancing its anisotropic carrier transport. The BPNR-FET shows a strong dependence on crystal orientation in which the best mobility performance is achieved in armchair-oriented nanoribbons. A downscaling of nanoribbon width is shown to improve the short-channel effect owing to a better electrostatic gate control. Furthermore, hydrogenation is employed to effectively passivate the dangling bonds and heal the nanoribbon edge defects, leading to nearly hysteresis-free transfer properties. By virtue of bandgap and contact-metal workfunction engineering, n-type BPNR-FET is successfully demonstrated, which enables complementary inverter circuits to be simultaneously realized. This paper unravels the superior performance underscores a conceptually new BPNR-FET, paving the way toward the development of non-planar devices and integrated circuits based on 2-D materials platform.

In this paper, we report on the assessment of self-amplified silicon–oxide–nitride–oxide–silicon (SONOS) memory device architecture for sub-50-nm gate length ( ${L}_{g}$ ) through calibrated simulations. Self-amplification (SA) effect in tunnel field-effect transistor-based SONOS (T-SONOS) memory device has been analyzed. Results show that memory window ( $\Delta {W}$ ) in T-SONOS cell increases as buried oxide thickness increases due to capacitive coupling between the front and back gates. Although the enhanced $\Delta {W}$ can also be achieved in inversion-mode SONOS (I-SONOS) device, its performance is deteriorated when the gate length is scaled down. We have compared the performance of I-SONOS and T-SONOS memory devices for ${L}_{g}$ varying from 100 to 25 nm. Results highlight that I-SONOS device cannot be programmed at ${L}_{g} ={25}$ nm and thus deteriorate the memory operation. However, SA T-SONOS at ${L}_{g} = {25}$ nm achieves ${W} \sim {6}$ V. In addition, the effect of underlap on the performance of T-SONOS cell has been analyzed, and it is shown that memory operation of 25-nm T-SONOS device can further improved with a drain side underlap of 20 nm. This paper provides new opportunities to design SA T-SONOS memory device for the next-generation nonvolatile memories.

In this paper, the pinning process of pinned photodiodes (PPDs) is described by a new analytical model, assuming the PPD to be composed of inner and junction regions. There are two definitions of the pinning potential: maximum conduction band potential variation ( $\Delta \varphi _{M}$ ) and maximum electron quasi-fermi level potential variation ( $\Delta $ FP $_{M}$ ). The output of the previous pinning potential models is only an approximation of $\Delta \varphi _{M}$ . In this paper, a comprehensive model is proposed in which both aforementioned definitions of pinning potential can be achieved analytically. The proposed model is a system of equations relating PPD’s main characteristics such as $\Delta \varphi _{M}$ and equilibrium full-well capacity to other main PPD parameters such as PPD spatial dimensions, impurity dopant concentrations, maximum inner region potential, and remnant carrier population at $\Delta \varphi _{M}$ . The proposed model is verified by two previously reported experiment-based data.

Many methods have been proposed for the experimental determination of the collector resistance in bipolar junction transistors and HBTs. In this paper, the most widely used methods are reviewed and applied to SiGe HBTs with a large variety of device sizes fabricated in different technologies and generations, including high-speed and high-voltage transistors. First, the accuracy of those methods, which are based on an extraction from single-transistor characteristics, is evaluated from simulated data using a sophisticated compact model and, where applicable, also device simulation. This approach allows the origin of observed inaccuracies or failures of certain methods to be identified. Second, the test structure-based methods are reviewed, and third, all methods were applied to experimental data. This paper and its results provide insight into each method’s accuracy; its application limits with respect to a technology, a device size, and an operating range as well as its requirements in terms of equipment and extraction effort.

This paper presents a new method for modeling the nonideal conductance response (CR) of synaptic devices. Unlike previous studies, which utilize physical device properties for modeling, this paper only uses the measured CR data. This allows the proposed modeling method to be easily applied to various types of synaptic devices without considering the unique physical properties of each device. An efficient piecewise linear approximation method which offers a tradeoff between computational complexity and simulation accuracy of neural networks is also presented to generate a linear device model out of nonlinear CR data. In addition, model parameters, which reflect the nonideal characteristics of the CR such as abrupt and asymmetric conductance changes, conductance variation, and limited conductance dynamic range, are introduced to evaluate the network performances in the presence of the nonidealities. By adjusting the model parameters, the desired CR satisfying the network performance requirements can be derived for device development. A three-layer neural network employing the device model has been designed and trained for the MNIST data set in order to demonstrate the application of the model to system-level simulations and verify the effectiveness of the modeling method.

This paper proposes a semianalytical model to estimate short-channel effects for independent gate operation in double-gate (DG) junctionless (JL) MOSFET incorporating gate-to-source/drain underlap, through the solution of Poisson’s equations in the subthreshold regime. The model also accounts for the asymmetry in device operation through variation in gate oxide thicknesses, gate work functions, and underlap lengths. Subthreshold drain current, threshold voltage, and subthreshold swing, evaluated from the channel potential, show reasonable agreement with simulation data. Results suggest the use of negative back gate bias and longer underlap length to reduce off-current. This paper highlights the role of doping, underlap length, and back gate bias in tuning the threshold voltage. This model serves as a generic formulation (within limits) with different asymmetries to estimate, design, and optimize self-aligned DG JL transistors for subthreshold logic applications.

Most thin-film transistor (TFT) gate drivers integrated on the display panel use the carry signals between the stages. In our previous works, we found that these carry-type gate drivers are subject to the reliability problem in a flexible display, since the errors of the stressed stages are accumulated through the carry signals. This problem possibly leads to the failure of image refresh of the display device. Therefore, the carry-free gate driver can resolve the error accumulation problem since it does not use the carry signals and instead, each unit stage operates independently. In this paper, we propose an advanced carry-free gate driver circuit to remove the drawbacks of the previous version, while keeping the advantages. More importantly, this paper is the first report to experimentally show that the error accumulation phenomenon of the carry-type gate driver and the problem is removed in the carry-free gate driver. The proposed carry-free gate driver and the carry-type gate driver are fabricated with amorphous indium-gallium-zinc-oxide TFTs on a flexible substrate for comparison purpose. The proposed gate driver shows a very high reliability since no voltage fluctuation occurs at the outputs after 10 000 cycles bending test with 2-mm bending radius.

Quantum dots (QDs) show a great potential for light-emitting diodes (LEDs) packaging, which still face great challenges compared with the matured phosphor downconversion materials. These are probably caused by the unique scattering and absorption properties of QDs, which are extremely different to the traditional phosphor due to their several nanometers size, while their effect on QDs-converted LEDs (QCLEDs) is barely studied. In this paper, we have experimentally and theoretically investigated the effect of scattering and absorption of CdSe/ZnS QDs on the optical performance for QCLEDs by comparing with the traditional yttrium aluminum garnet phosphor. Results indicate that the strong absorption (reabsorption) of QDs causes low radiant efficacy and stability for QCLEDs; their weak scattering also leads to a low color uniformity. It demonstrates that their unique scattering and absorption properties are key factors leading to low optical performance of QCLEDs compared with the traditional phosphor-converted LEDs. For purpose of gaining the white LED with high efficiency and stability, it is highly suggested to use a low QD concentration to reduce the reabsorption loss and the total internal reflection loss. We believe that this paper can provide a better understanding of improving the optical performance for QCLEDs from the prospective of scattering and absorption. In the future, it is important to use low QD concentration to gain high-performance white LEDs with high downconversion efficiency by optimizing packaging structures.

A high-harmonic traveling-wave tube (HHTWT) is designed, developed, and tested in this paper. This device is configured as a multiplier–amplifier with Q-band input signals and its third harmonic, i.e., D-band output power. The tested result demonstrates that 280 mW at 133.5 GHz is obtained as a result of 200 mW at 44.5-GHz input signal. The simulation and experiment validate that the high-harmonic radiation can be generated and amplified in the HHTWT. The approach described in this paper could find application in exploring high power, wideband tunable terahertz source. This paper is expanded from a conference paper on IVEC 2017. The detail design produce and tested result are added in this paper. The explanation of the simulation and tested results is also presented.

Single-stage depressed collector systems are widely used in high-power gyrotrons in order to increase the overall efficiency. The position where the deceleration of the beam takes place influences the collector efficiency. In this paper, several deceleration schemes are numerically investigated for the short-pulse prototype of the 170-GHz, 1-MW European gyrotron for International Thermonuclear Experimental Reactor. The results of this paper are in a qualitative agreement with the results of dedicated experiments. A simple idea is also proposed for the significant increase of the overall gyrotron efficiency without an important technological modification.