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![(a) Schematic diagrams of CMOS inverter structure; (b) Conceptual CMOS inverter device structure in one material; (c) Transfer characteristics of the CMOS inverter (adapted from [89] with permission from Springer Nature); (d) Schematic diagrams of a zero-VGS inverter structure; (e) Schematic diagrams of a diode-load inverter structure; (f) Schematic diagrams of a Pseudo-D inverter structure; (g) Schematic diagrams of a Pseudo-E inverter structure; (h) Optical image of a zero-VGS inverter (adapted from [90] with permission from Elsevier B.V.); (i) ZTO TFTs transfer characteristics of a zero-VGS inverter (adapted from [91] with permission from AIP Publishing); (j) IGZO TFTs with ZAO insulator transfer characteristics of a zero-VGS inverter (adapted from [92] with permission from John Wiley and Sons).](publication/358362854/figure/fig5/AS:1127743550951428@1645886423610/a-Schematic-diagrams-of-CMOS-inverter-structure-b-Conceptual-CMOS-inverter-device.jpg)
(a) Schematic diagrams of CMOS inverter structure; (b) Conceptual CMOS inverter device structure in one material; (c) Transfer characteristics of the CMOS inverter (adapted from [89] with permission from Springer Nature); (d) Schematic diagrams of a zero-VGS inverter structure; (e) Schematic diagrams of a diode-load inverter structure; (f) Schematic diagrams of a Pseudo-D inverter structure; (g) Schematic diagrams of a Pseudo-E inverter structure; (h) Optical image of a zero-VGS inverter (adapted from [90] with permission from Elsevier B.V.); (i) ZTO TFTs transfer characteristics of a zero-VGS inverter (adapted from [91] with permission from AIP Publishing); (j) IGZO TFTs with ZAO insulator transfer characteristics of a zero-VGS inverter (adapted from [92] with permission from John Wiley and Sons).
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Thin−film transistors using metal oxides have been investigated extensively because of their high transparency, large area, and mass production of metal oxide semiconductors. Compatibility with conventional semiconductor processes, such as photolithography of the metal oxide offers the possibility to develop integrated circuits on a larger scale. I...
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... inverter is a logic element in which output voltage has a value opposite to the input voltage and is the most basic circuit for designing a logic circuit [84][85][86]. A complementary metal-oxide-semiconductor (CMOS) inverter logic device consists of one n-type metal-oxide semiconductor (NMOS) as a pull-down operation and one p-type metal-oxide semiconductor (PMOS) as pull-up operation (Figure 5a). Most metal-oxide semiconductors, such as IGZO, ZTO, and ZnO, exhibit typical n-type characteristics. ...
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... to the limitations of these semiconductor materials, research to implement inverters with only n-type oxide semiconductors is being actively conducted [88]. The four circuit schemes were reported: (1) zero-VGS, (2) diode-load, (3) Pseudo-D, and (4) Pseudo-E (Figure 5d-g). This chapter introduces an inverter based on a metal-oxide semiconductor. ...
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... et al. controlled the concentration of OH groups in the gate dielectric to control the carrier polarity and accordingly implement controllable n-type and p-type TFTs with the CMOS inverter circuit (Figure 5b) [89]. Tin oxide was used for both the n-type and p-type TFTs; the semiconductor properties were controlled by modulating the concentration of OH groups in the gate dielectric. ...
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... et al. presented a large-scale, high-performance IGZO dot TFT using inkjet printing technology and implemented an NMOS inverter (Figure 5h) [90]. The mobility of the IGZO TFT was reported to 28.44 cm 2 /Vs. ...
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... inverter showed performance at a maximum voltage gain of 112 V/V. Han et al. implemented a high-performance inverter composed of ZTO TFTs and SZTO TFTs (Figure 5i) [91]. The ZTO TFT was operated as a driver transistor in enhancement mode, and the mobility was obtained to 23.6 cm 2 /Vs. ...
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... SZTO TFT operated as a load transistor in the depletion mode, and the mobility was 18.4 cm 2 /Vs. The inverter showed a high voltage gain of 25.22 v/v and a narrow transition width at an operating voltage of 10 V. Islam et al. fabricated a-IGZO TFT from high dielectric constant zinc aluminum oxide (ZAO) using low-cost spray pyrolysis technology for large area and low power (Figure 5j) [92]. The fabricated TFT had a mobility of 15.04 cm 2 /Vs and a high I on/off ratio (>10 8 ). ...
Citations
... With the end of Moore's Law, integrated circuits have shifted from blindly pursuing an increase in integration to enhancing intelligence [1]. Intelligent electronics, including smart wearable devices, energy storage devices, sensors, and smart fabrics, are typically adhered to structures or biological surfaces to obtain more accurate sensing signals and enhanced wear comfort, which demands greater flexibility from these circuits [2][3][4]. Additionally, the superb conformal ability of flexible circuits allows them to adhere to the curved surfaces of three-dimensional objects without being limited by installation space. For example, conformal circuits can be applied to radar antennas on aircraft surfaces, structural health monitoring sensors, etc., significantly reducing equipment weight and enhancing aerodynamic performance [5][6][7][8]. ...
To meet the demand for higher performance and wearability, integrated circuits are developing towards having multilayered structures and greater flexibility. However, traditional circuit fabrication methods using etching and lamination processes are not compatible with flexible substrates. As a non-contact printing method in additive manufacturing, electrohydrodynamic printing possesses advantages such as environmental friendliness, sub-micron manufacturing, and the capability for flexible substrates. However, the interconnection and insulation of different conductive layers become significant challenges. This study took composite silver ink as a conductive material to fabricate a circuit via electrohydrodynamic printing, applied polyimide spraying to achieve interlayer insulation, and drilled micro through-holes to achieve interlayer interconnection. A 200 × 200 mm2 ten-layer flexible circuit was thus prepared. Furthermore, we combined a finite element simulation with reliability experiments, and the prepared ten-layer circuit was found to have excellent bending resistance and thermal cycling stability. This study provides a new method for the manufacturing of low-cost, large-sized, multilayer flexible circuits, which can improve circuit performance and boost the development of printed electronics.
... Stretchable devices and wearable strain sensors are garnering increasing interest across diverse sectors, ranging from healthcare to robotics [1][2][3][4][5]. Traditionally, such devices have relied heavily on metal-based materials or semiconductors integrated with micro/nanostructures [6][7][8]. Despite the superior electrical and mechanical properties of these materials, they present restrictions in durability, elasticity, and reusability. ...
Polymers mixed with conductive fillers hold significant potential for use in stretchable and wearable sensor devices. Enhancing the piezoresistive effect and mechanical stability is critical for these devices. To explore the changes in the electrical resistance under high strains, typically unachievable in single-layer composites, bi-layer structures were fabricated from carbon nanotubes (CNTs) and EcoFlex composites to see unobservable strain regions. Spherical types of non-conductive fillers composed of polystyrene and conductive filler, coated with Ni and Au on non-conductive fillers, were used as secondary fillers to improve the piezoresistive sensitivity of composites, and their respective impact on the conductive network was compared. The electrical and mechanical properties were examined in the static state to understand the impact of these secondary fillers. The changes in the electrical resistance under 100% and 300% tensile strain, and their dependence on the inherent electrical properties of the secondary fillers, were also investigated. Single-layer CNT composites proved incapable of withstanding 300% strain, whereas the bi-layer structures proved resilient. By implementing cyclic stretching tests, contrary to non-conductive fillers, reduced piezoresistive influence of the conductive secondary filler under extreme strain conditions could be observed.
... Organic electronic devices were developed many years ago, starting from OLED applications in displays [95], followed by integrated electronic devices on flexible substrates [96], organic solar cells [97], biocompatible devices [98], biomimetic devices [99], and more applications of these transistors in the field of biosensors [100,101]. ...
... Recent research proposed a neuro-device [127] that opens the doors toward artificial synapses but is simultaneously sensitive to the DA concentration. This is a real development in biomimetic devices [99], serving the goals of neuromorphic electronics [96]. In this discussed case, the device is operated as a DA biosensor, reaching ultra-low detection limits, sub 1 pM [127]. ...
Neurotransmitters are an important category of substances used inside the nervous system, whose detection with biosensors has been seriously addressed in the last decades. Dopamine, a neurotransmitter from the catecholamine family, was recently discovered to have implications for cardiac arrest or muscle contractions. In addition to having many other neuro-psychiatric implications, dopamine can be detected in blood, urine, and sweat. This review highlights the importance of biosensors as influential tools for dopamine recognition. The first part of this article is related to an introduction to biosensors for neurotransmitters, with a focus on dopamine. The regular methods in their detection are expensive and require high expertise personnel. A major direction of evolution of these biosensors has expanded with the integration of active biological materials suitable for molecular recognition near electronic devices. Secondly, for dopamine in particular, the miniaturized biosensors offer excellent sensitivity and specificity and offer cheaper detection than conventional spectrometry, while their linear detection ranges from the last years fall exactly on the clinical intervals. Thirdly, the applications of novel nanomaterials and biomaterials to these biosensors are discussed. Older generations, metabolism-based or enzymatic biosensors, could not detect concentrations below the micro-molar range. But new generations of biosensors combine aptamer receptors and organic electrochemical transistors, OECTs, as transducers. They have pushed the detection limit to the pico-molar and even femto-molar ranges, which fully correspond to the usual ranges of clinical detection of human dopamine in body humors that cover 0.1 ÷ 10 nM. In addition, if ten years ago the use of natural dopamine receptors on cell membranes seemed impossible for biosensors, the actual technology allows co-integrate transistors and vesicles with natural receptors of dopamine, like G protein-coupled receptors. The technology is still complicated, but the uni-molecular detection selectivity is promising.
... Solution-processed indium-zinc-oxide (IZO) metal-oxide semiconductors have emerged as promising materials for a wide range of electronic applications, including transparent conductive films, thin-film transistors (TFTs), and photovoltaic devices [1][2][3][4]. These metaloxide semiconductors exhibit desirable properties such as high field-effect mobility, optical transparency, and the potential for direct printing, making them ideal for next-generation electronic devices [5][6][7][8]. ...
Understanding the density of state (DOS) distribution in solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs) is crucial for addressing electrical instability. This paper presents quantitative calculations of the acceptor-like state distribution of solution-processed IZO TFTs using thermal energy analysis. To extract the acceptor-like state distribution, the electrical characteristics of IZO TFTs with various In molarity ratios were analyzed with respect to temperature. An Arrhenius plot was used to determine electrical parameters such as the activation energy, flat band energy, and flat band voltage. Two calculation methods, the simplified charge approximation and the Meyer–Neldel (MN) rule-based carrier–surface potential field-effect analysis, were proposed to estimate the acceptor-like state distribution. The simplified charge approximation established the modeling of acceptor-like states using the charge–voltage relationship. The MN rule-based field-effect analysis validated the DOS distribution through the carrier–surface potential relationship. In addition, this study introduces practical and effective approaches for determining the DOS distribution of solution-processed IZO semiconductors based on the In molarity ratio. The profiles of the acceptor-like state distribution provide insights into the electrical behavior depending on the doping concentration of the solution-processed IZO semiconductors.
... Wide-bandgap oxide semiconductors (OSs) are widely investigated as promising channel layers of thin-film transistors (TFTs) in display technology [1,2], artificial synapses [3], sensors [4], Schottky devices [5] and other applications [6][7][8]. Among them, indium-gallium-zinc oxide (IGZO) TFTs have become the backplane standard for activematrix liquid-crystal displays and active-matrix organic lightemitting diode displays because of their reasonable mobility (µ FE > 10 cm 2 V −1 s −1 ), high I on/off ratio (>10 8 ), extremely low leakage current (<10 −15 A), low process temperature (<350 • C), high uniformity, and large-area scalability [9][10][11]. ...
Indium oxide (In 2 O 3 ) thin films sputtered at room temperature were annealed under different atmospheres and examined for thin-film transistor (TFT) active channel applications. The annealing process was performed in a rapid thermal annealing system at 350 °C under O 2 , Ar, forming gas (FG, 96% N 2 /4% H 2 ), and N 2 . It was found that the annealed In 2 O 3 TFTs exhibited high field-effect mobility (μFE >40 cm ² V ⁻¹ s ⁻¹ ), high on/off current ratio (Ion/off ~10 ⁸ ), and controlled threshold voltage (V TH ) for the enhancement- and depletion-mode operations. Note that the annealing atmosphere has a significant effect on the electrical performance of the In 2 O 3 TFTs by inducing changes in oxygen-related species, particularly oxygen vacancies (V O ) and hydroxyl/carbonate species (O–H/C–O). For the O 2 -, Ar-, FG-, and N 2 -annealed TFTs, μFE was in increasing order accompanied by a negative shift in V TH , which is a result attributed to the larger V O in the In 2 O 3 thin films. Furthermore, the ΔV TH of the FG-, and N 2 -annealed TFTs in a positive bias stress (PBS) test was greater than that of the O 2 -, Ar-annealed devices, attributing to their lower density of O–H/C–O groups in the In 2 O 3 thin films. Our results suggest that the annealing atmosphere contributes to the internal modifications of the In 2 O 3 structure and in turn altered the electrical characteristics of TFTs. These annealed In 2 O 3 TFTs with high performance are promising candidates for realizing large-area, transparent, and high-resolution displays.
... Overall, our simulation results suggest that such earth-abundant all-metal oxide HBT offers several advantages such as low power consumption and high-frequency characteristics, which can be employed as a transistor switch in transparent display technologies, e. g., OLEDs [83]. Considering the proportionate traits of the proposed and OLED devices, both of them can be fabricated on a flexible substrate and enjoy jointly bendable, conformable, foldable, cost-effective, and lightweight attributes [84]. Therefore, the proposed transistor switch of the OLEDs can be yielded flexible and affordable in turn with high throughput. ...
Oxide semiconductor-based heterojunction bipolar transistors are widely applicable in flexible, printable, and cost-effective circuit applications. Among earth-abundant metal oxides, zinc oxide and copper oxide inherently show n-type and p-type characteristics, respectively, and their electronic properties can be easily modified during the fabrication process. Accordingly, a planar-type HBT can be achieved by low-temperature growth of the metal-oxide layers on a flexible substrate without the need for further sophisticated processes. In this paper, a double heterojunction bipolar transistor (DHBT) comprised of ZnO layers serving as the emitter and collector regions, along with the CuO layer functioning as the base area is presented. Simulation results demonstrate that the proposed all-metal oxide transistor based on p-CuO/n-ZnO heterojunction enjoys low power consumption owing to the low threshold voltage. High-frequency characterization and DC analysis of the proposed NPN configuration are carried out using the ATLAS/SILVACO package. Our findings reveal that at the base-emitter voltage of 0.55 V, the current gain factor of the device reaches 155, which is larger than those reported in the literature. Furthermore, an ideality factor at the base-emitter voltage of 0.7 V was obtained for the collector-base and emitter-base junctions equal to 1.5 and 1.2, respectively.
... Metal-Oxides (MO) materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] high-k dielectrics, 20 passivation materials, 21 and organic substrates 22 dramatically decreased cost and/or improved the achieved and projected TFT performance. The low field mobility of oxide materials has approached 150 cm 2 /Vs. ...
Novel metal oxide materials such as InGaZnO (IGZO), ZnO, SnO, and In2O3 and improved fabrication processes dramatically enhanced the achieved and projected thin film transistor (TFT) performance. The recorded values of the effective field-effect mobility of metal oxide TFT (MOTFT) materials have approached 150 cm2/Vs. We report on an improved compact TFT model based on three models: the RPI TFT model, the unified charge control model (UCCM), and the multi-segment TFT compact model. This improved model accounts for a non-exponential slope in the subthreshold regime by introducing a varying subthreshold slope and accounts for non-trivial capacitance dependence on the gate bias, and parasitic impedances. The analysis of the TFT response using this model and the analytical calculations show that TFTs could have a significant response to impinging THz and sub-THz radiation. Using a complementary inverter and the phase-matched THz signal feeding significantly improves the detection sensitivity.
... At the beginning of the 4th industrial revolution, there is increasing interest in next-generation wearable devices capable of providing real-time healthcare monitoring [1][2][3] . Because they can be carried close to the body, such devices enable diagnosis and prevention as well as treatment. ...
... It can be summarized using Eqs. (2)(3)(4)(5), where f FR and f TI are the FR and TI factor, R 1 , ϕ 1 are the reflectance and phase difference at the opposite interface of the emitted light direction, T 2 , R 2 , ϕ 2 are the transmittance, reflectance, and phase difference at the boundary where the light is emitted, Δϕ is the phase difference of the repeatedly reflected light at the upper and lower boundaries, λ is the wavelength of the light, n 0 and d 0 are the refractive index and thickness of the layer where the cavity occurs, and θ is the propagated light angle. ...
Increasing demand for real-time healthcare monitoring is leading to advances in thin and flexible optoelectronic device-based wearable pulse oximetry. Most previous studies have used OLEDs for this purpose, but did not consider the side effects of broad full-width half-maximum (FWHM) characteristics and single substrates. In this study, we performed SpO 2 measurement using a fiber-based quantum-dot pulse oximetry (FQPO) system capable of mass production with a transferable encapsulation technique, and a narrow FWHM of about 30 nm. Based on analyses we determined that uniform angular narrow FWHM-based light sources are important for accurate SpO 2 measurements through multi-layer structures and human skin tissues. The FQPO was shown to have improved photoplethysmogram (PPG) signal sensitivity with no waveguide-mode noise signal, as is typically generated when using a single substrate (30–50%). We successfully demonstrate improved SpO 2 measurement accuracy as well as all-in-one clothing-type pulse oximetry with FQPO.
... Conventional silicon-based transistors have some limitations and difficulties, i.e., "limited form-factor, the difficulty of the large-area process, and high-cost complex-to-fabricate process". Hence, the advantages of metal-oxide-based transistors make them a suitable candidate for the next generation of thin-film transistors (TFTs) for foldable, flexible, and stretchable displays and other electronic products [27]. The MOS could be either p-type or ntype polycrystalline silicon metals. ...
Semiconductors are the basic building block and basic elements of modern electrical devices and machines. N-type metal oxide semiconductor (MOS) is particularly interesting due to their unique properties and wide applications. Because of their enormous applications and importance, semiconductors are believed to play a major role in facilitating modern life. Medicine, agriculture, mechanics, nuclear energy, biotechnology, communications, and data operations are among the areas that benefit most from the application of semiconductors. Hence, this review attempts to summarize the important features of semiconductors in general and MOS nanoparticles in particular, their structure and properties. The applications of MOS and the thin-film transistor are summarized with emphasis on their applications as photocatalysts for bioremediation, solar and hydrogen cells, and sensor devices.
... In particular, the concept of the Metaverse makes wearable devices, flexible smart sensors, and electronic skins attract great interest [11]. With the development of transferable single-crystal SiNMs, flexible TFTs have become an essential and fundamental element for most of the flexible applications [12][13][14][15][16][17][18][19][20][21][22][23]. ...
We fabricate a flexible silicon thin-film transistor (TFT) on a plastic substrate as a key component and representative example to analyze the major influencing factors of flexible devices under bending conditions. Experimental and two-dimensional device modeling results reveal that bending radius and device dimensions have a significant influence on the radio-frequency (RF) performance of the flexible silicon nanomembrane (SiNM) TFT under bending conditions. Carrier mobility and electric field extracted from the model, together with theoretical analysis, were employed to study the performance dependence and the operation mechanisms of the bended TFTs. The carrier mobility and electric field are increased monotonically with larger bending strains, which lead to better RF performance. They also showed a consistent change trend with different device parameters (e.g., gate length, oxide thickness). Flexible SiNM TFTs with a smaller gate length and a larger gate dielectric thickness are shown to have better RF performance robustness with bending strains. The analysis provides a guideline for the study of flexible electronics under bending conditions.
