Abstract Von Neumann architecture-based computing, while widely successful in personal computers and embedded systems, faces inherent challenges including the von Neumann bottleneck, particularly ...amidst the ongoing surge of data-intensive tasks. Neuromorphic computing, designed to integrate arithmetic, logic, and memory operations, has emerged as a promising solution for improving energy efficiency and performance. This approach requires the construction of an artificial synaptic device that can simultaneously perform signal processing, learning, and memory operations. We present a photo-synaptic device with 32 analog multi-states by exploiting field-effect transistors based on the lateral heterostructures of two-dimensional (2D) WS 2 and MoS 2 monolayers, formed through a two-step metal–organic chemical vapor deposition process. These lateral heterostructures offer high photoresponsivity and enhanced efficiency of charge trapping at the interface between the heterostructures and SiO 2 due to the presence of the WS 2 monolayer with large trap densities. As a result, it enables the photo-synaptic transistor to implement synaptic behaviors of long-term plasticity and high recognition accuracy. To confirm the feasibility of the photo-synapse, we investigated its synaptic characteristics under optical and electrical stimuli, including the retention of excitatory post-synaptic currents, potentiation, habituation, nonlinearity factor, and paired-pulse facilitation. Our findings suggest the potential of versatile 2D material-synapse with a high density of device integration.
A two-dimensional molybdenum disulfide (MoS
2
)-based gas sensor was decorated with Pt nanoparticles (NPs) for high sensitivity and low limit of detection (LOD) for specific gases (NH
3
and H
2
S). ...The two-dimensional MoS
2
film was grown at 400°C using metal organic gas vapour deposition. To fabricate the MoS
2
gas sensor, an interdigitated Au/Ti electrode was deposited using the electron beam (e-beam) evaporation method with a stencil mask. The MoS
2
gas sensor without metal decoration sensitively detects NH
3
and H
2
S gas down to 2.5 and 30 ppm, respectively, at room temperature (RT). However, for improved detection of NH
3
and H
2
S gas, we investigated the functionalization strategy using metal decoration. Pt NP decoration modulated the electronic properties of MoS
2
, significantly improving the sensitivity of NH
3
and H
2
S gas by 5.58× and 4.25×, respectively, compared with the undecorated MoS
2
gas sensor under concentrations of 70 ppm. Furthermore, the Pt NP-decorated MoS
2
sensor had lower LODs for NH
3
and H
2
S gas of 130 ppb and 5 ppm, respectively, at RT.
Gas sensors applied in real-time detection of toxic gas leakage, air pollution, and respiration patterns require a reliable test platform to evaluate their characteristics, such as sensitivity and ...detection limits. However, securing reliable characteristics of a gas sensor is difficult, owing to the structural difference between the gas sensor measurement platform and the difference in measurement methods. This study investigates the effect of measurement conditions and system configurations on the sensitivity of two-dimensional (2D) material-based gas sensors. Herein, we developed a testbed to evaluate the response characteristics of MoS
-based gas sensors under a NO
gas flow, which allows variations in their system configurations. Additionally, we demonstrated that the distance between the gas inlet and the sensor and gas inlet orientation influences the sensor performance. As the distance to the 2D gas sensor surface decreased from 4 to 2 mm, the sensitivity of the sensor improved to 9.20%. Furthermore, when the gas inlet orientation was perpendicular to the gas sensor surface, the sensitivity of the sensor was the maximum (4.29%). To attain the optimum operating conditions of the MoS
-based gas sensor, the effects of measurement conditions, such as gas concentration and temperature, on the sensitivity of the gas sensor were investigated.
•3D-nanostructured MoS2 is grown using metal-organic chemical vapor deposition.•The 3D-nanostructured MoS2 (3DN-MoS2) is rolled via an ethanol drop-casting process.•The MoS2 nanoscroll self-assembles ...in the direction of high strain energy.•The scrolling of 3DN-MoS2 leads to opened active sites in nanostructure interlayers.•This technology enables low concentration toxic gas detection at room temperature.
Assembly operations can transform simple structures into complicated topologies such as crumples, folds, and scrolls, offering extraordinary electronic and optical properties. Two-dimensional (2D) transition metal dichalcogenides (TMDC) nanoscrolls have attracted attention for their distinctive and excellent characteristics. However, their chemically inert surface limits scalability in various applications. This study exploits the scrolling characteristics of three-dimensional nanostructured 2D MoS2 (3DN-MoS2) to improve NO2 detection. By growing 3DN-MoS2 and applying high strain energy through an ethanol solution-based drop-casting process, the material self-assembles in the direction of high strain energy. To confirm the applicability of opened active sites in nanostructure interlayers, we fabricated a scrolled 3DN-MoS2 gas sensor, demonstrating a 28-fold sensitivity enhancement compared to pristine 3DN-MoS2. The unique assembly operation of nanostructures enables versatile applications, including the detection of toxic gases at low concentrations and low operating temperatures.
In this paper, a novel method is proposed for increasing the performance through coupling of top-down models adjusting the object detector based on a new loss function. Generally, object detectors ...and keypoint estimators are sequentially used in real-time multi-person pose estimations; however, these two models are separately trained. Therefore, the results of the object detector are not optimized for the keypoint estimator. To solve this problem, we analyze the relationship between the two models and propose a feedback-based loss optimization in the object detector, based on the estimation results of the keypoint estimator. In addition, the resulting bounding box of the object detector is readjusted to improve the accuracy of the keypoint estimation model. The experimental results demonstrate that the proposed approach can perform real-time operations with a high frame rate similar to that of the baseline model. Moreover, it achieved an accuracy of 74.2 average precision (AP), which is higher than the state-of-the-arts model including the human detector used in the experiment.
•A novel method for increasing the performance through adjusting the object detector based on a new loss function is proposed.•It is based on an optimization through the estimation results of the keypoint estimator.•It achieved an accuracy of 74.2 average precision (AP), which is higher than the state-of-the-arts model including the human detector used in the experiment.•It can perform real-time operations with a high frame rate similar to that of the baseline model.
Hardware security is not a new problem but is ever-growing in consumer and medical domains owing to hyperconnectivity. A physical unclonable function (PUF) offers a promising hardware security ...solution for cryptographic key generation, identification, and authentication. However, electrical PUFs using nanomaterials or two-dimensional (2D) transition metal dichalcogenides (TMDCs) often have limited entropy and parameter space sources, both of which increase the vulnerability to attacks and act as bottlenecks for practical applications. We report an electrical PUF with enhanced entropy as well as parameter space by incorporating 2D TMDC heteronanostructures into field-effect transistors (FETs). Lateral heteronanostructures of 2D molybdenum disulfide and tungsten disulfide serve as a potent entropy source. The variable feature of FETs is further leveraged to enhance the parameter space that provides multiple challenge–response pairs, which are essential for PUFs. This combination results in stably repeatable yet highly variable FET characteristics as alternative electrical PUFs. Comprehensive PUF performance analyses validate the bit uniformity, reproducibility, uniqueness, randomness, false rates, and encoding capacity. The 2D material heteronanostructure-driven electrical PUFs with strong FET-to-FET variability can potentially be augmented as an immediately deployable and scalable security solution for various hardware devices.
Von Neumann architecture-based computing, while widely successful in personal computers and embedded systems, faces inherent challenges including the von Neumann bottleneck, particularly amidst the ...ongoing surge of data-intensive tasks. Neuromorphic computing, designed to integrate arithmetic, logic, and memory operations, has emerged as a promising solution for improving energy efficiency and performance. This approach requires the construction of an artificial synaptic device that can simultaneously perform signal processing, learning, and memory operations. We present a photo-synaptic device with 32 analog multi-states by exploiting field-effect transistors based on the lateral heterostructures of two-dimensional (2D) WS
and MoS
monolayers, formed through a two-step metal-organic chemical vapor deposition process. These lateral heterostructures offer high photoresponsivity and enhanced efficiency of charge trapping at the interface between the heterostructures and SiO
due to the presence of the WS
monolayer with large trap densities. As a result, it enables the photo-synaptic transistor to implement synaptic behaviors of long-term plasticity and high recognition accuracy. To confirm the feasibility of the photo-synapse, we investigated its synaptic characteristics under optical and electrical stimuli, including the retention of excitatory post-synaptic currents, potentiation, habituation, nonlinearity factor, and paired-pulse facilitation. Our findings suggest the potential of versatile 2D material-synapse with a high density of device integration.
Inverse‐vulcanized polymeric sulfur has received considerable attention for application in waste‐based infrared (IR) polarizers with high polarization sensitivities, owing to its high transmittance ...in the IR region and thermal processability. However, there have been few reports on highly sensitive polymeric sulfur‐based polarizers by replication of pre‐simulated dimensions to achieve a high transmission of the transverse magnetic field (TTM) and extinction ratio (ER). Herein, a 400‐nanometer‐pitch mid‐wavelength infrared bilayer linear polarizer with self‐aligned metal gratings is introduced on polymeric sulfur gratings integrated with a spacer layer (SM‐polarizer). The dimensions of the SM‐polarizer can be closely replicated using pre‐simulated dimensions via a systematic investigation of thermal nanoimprinting conditions. Spacer thickness is tailored from 40 to 5100 nm by adjusting the concentration of polymeric sulfur solution during spin‐coating. A tailored spacer thickness can maximize TTM in the broadband MWIR region by satisfying Fabry–Pérot resonance. The SM‐polarizer yields TTM of 0.65, 0.59, and 0.43 and ER of 3.12 × 103, 5.19 × 103, and 5.81 × 103 at 4 µm for spacer thicknesses of 90, 338, and 572 nm, respectively. This demonstration of a highly sensitive and cost‐effective SM‐polarizer opens up exciting avenues for infrared polarimetric imaging and for applications in polarization manipulation.
Inverse‐vulcanized polymeric sulfur can replace expensive commercial semiconductors and chalcogenides for mid‐wavelength infrared applications. Here, a highly sensitive and cost‐effective polymeric‐sulfur‐based bilayer wire‐grid linear polarizer with a pitch of 400 nm is successfully demonstrated by systematically investigated thermal nanoimprinting conditions and precisely changed spacer thickness to control Fabry‐Pérot resonance.
Batch growth of high-mobility (μFE > 10 cm2V–1s–1) molybdenum disulfide (MoS2) films can be achieved by means of the chemical vapor deposition (CVD) method at high temperatures (>500 °C) on rigid ...substrates. Although high-temperature growth guarantees film quality, time- and cost-consuming transfer processes are required to fabricate flexible devices. In contrast, low-temperature approaches (<250 °C) for direct growth on polymer substrates have thus far achieved film growth with limited spatial homogeneity and electrical performance (μFE is unreported). The growth of a high-mobility MoS2 film directly on a polymer substrate remains challenging. In this study, a novel low-temperature (250 °C) process to successfully overcome this challenge by kinetics-controlled metal–organic CVD (MOCVD) is proposed. Low-temperature MOCVD was achieved by maintaining the flux of an alkali-metal catalyst constant during the process; furthermore, MoS2 was directly synthesized on a polyimide (PI) substrate. The as-grown film exhibits a 4 in. wafer-scale uniformity, field-effect mobility of 10 cm2V–1s–1, and on/off ratio of 105, which are comparable with those of high-temperature-grown MoS2. The directly fabricated flexible MoS2 field-effect transistors demonstrate excellent stability of electrical properties following a 1000 cycle bending test with a 1 mm radius.
In the era of hyperconnected contemporary society, hardware and information security become more dependent on advanced cryptographic primitives. A physically unclonable function (PUF), originally ...implemented by an algorithmic means as software-based security, is considered as an immediate security solution. Nanomaterial-based PUFs have recently received considerable attention but have often limitations on unclonability and scalability for practical applications. Here, we report that heteronanostructures of vertically orientated molybdenum disulfide (MoS2) nanoflakes and titanium dioxide (TiO2) aggregates can be used for a versatile PUF. The band alignment of heteronanostructured MoS2/TiO2 results in photogenerated electron transfer and turns off the bright state of emitters, offering an entropy source. After von Neumann debiasing, extracted cryptographic keys show a large encoding capacity and reliable PUF performance, including randomness, uniqueness, reproducibility, low false rates, and long-term stability. The unique hybridization of the most common semiconductor nanomaterials could not only offer inherent asymmetry not to be cloned for a PUF but also guarantee scalable nanomanufacturing strategies to augment cryptosystems.
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