Column Row Convolutional Neural Network: Reducing Parameters for Efficient Image Processing.

Recent advancements in deep learning have achieved significant progress by increasing the number of parameters in a given model. However, this comes at the cost of computing resources, prompting researchers to explore model compression techniques that reduce the number of parameters while maintaining or even improving performance. Convolutional neural networks (CNN) have been recognized as more efficient and effective than fully connected (FC) networks. We propose a column row convolutional neural network (CRCNN) in this letter that applies 1D convolution to image data, significantly reducing the number of learning parameters and operational steps. The CRCNN uses column and row local receptive fields to perform data abstraction, concatenating each direction's feature before connecting it to an FC layer. Experimental results demonstrate that the CRCNN maintains comparable accuracy while reducing the number of parameters and compared to prior work. Moreover, the CRCNN is employed for one-class anomaly detection, demonstrating its feasibility for various applications.

Area-Selective Chemical Doping on Solution-Processed MoS2 Thin-Film for Multi-Valued Logic Gates.

Multi-valued logic gates are demonstrated on solution-processed molybdenum disulfide (MoS2) thin films. A simple chemical doping process is added to the conventional transistor fabrication procedure to locally increase the work function of MoS2 by decreasing sulfur vacancies. The resulting device exhibits pseudo-heterojunctions comprising as-processed MoS2 and chemically treated MoS2 (c-MoS2). The energy-band misalignment of MoS2 and c-MoS2 results in a sequential activation of the MoS2 and c-MoS2 channel areas under a gate voltage sweep, which generates a stable intermediate state for ternary operation. Current levels and turn-on voltages for each state can be tuned by modulating the device geometries, including the channel thickness and length. The optimized ternary transistors are incorporated to demonstrate various ternary logic gates, including the inverter, NMIN, and NMAX gates.

Commensurate Assembly of C60 on Black Phosphorus for Mixed-Dimensional van der Waals Transistors.

2D crystals can serve as templates for the realization of new van der Waals (vdW) heterostructures via controlled assembly of low-dimensional functional components. Among available 2D crystals, black phosphorus (BP) is unique due to its puckered atomic surface topography, which may lead to strong epitaxial phenomena through guided vdW assembly. Here, it is demonstrated that a BP template can induce highly oriented assembly of C60 molecular crystals. Transmission electron microscopy and theoretical analysis of the C60 /BP vdW heterostructure clearly confirm that the BP template results in oriented C60 assembly with higher-order commensurism. Lateral and vertical devices with C60 /BP junctions are fabricated via a lithography-free clean process, which allows one to investigate the ideal electrical properties of pristine C60 /BP junctions. Effective tuning of the C60 /BP junction barrier from 0.2 to 0.5 eV and maximum on-current density higher than 104  mA cm-2 are achieved with graphite/C60 /BP vertical vdW transistors. Due to the formation of high-quality C60 film and the semitransparent graphite top-electrode, the vertical transistors show high photoresponsivities up to ≈100 A W-1 as well as a fast response time under visible light illumination.

Cold-Trap-Mediated Broad Dynamic Photodetection in Graphene-Organic Hybrid Photonic Barristors.

One of the most popular approaches to improve the performance of organic photonic devices has been to control the electrically heterogeneous charge-transferring interfaces via chemical modifications. Despite intense research efforts, however, the rapid pace of material evolution through the chemical versatility of the organic compound allows only limited room for the fine-tuning of the interfaces exclusive to specific materials. This limitation leads to an ill-controlled charge recombination behavior that relies solely on the inherent characteristics of each material; thus, the common device architecture cannot harness its full potential. In this work, we demonstrate the use of a graphene-organic hybrid barristor-type phototriode architecture as an alternative platform to realize a linearly and highly photosensitive photodetector operating in a broad dynamic range with rapid temporal responses. With the capability of interfacial energetic modulation, our model system exhibits the dominance of swiftly saturable and slowly responding "cold" traps (TC < 3kT) in charge recombination behaviors, leading to a broad linear dynamic range of 110 dB as well as unconventional illumination-driven increments of both D* and R up to 1013 Jones and 360 mA/W, respectively, that surpass the best-reported organic photodiodes. Our findings demonstrate that the organic-graphene hybrid photonic barristor architecture can open new avenues to design high-performance photodetectors for various photonic applications in the future.

Percolation-Limited Dual Charge Transport in Vertical p-n Heterojunction Schottky Barrier Transistors.

Solution-processed, high-speed, and polarity-selective organic vertical Schottky barrier (SB) transistors and logic gates are presented. The organic layer, which is a bulk heterojunction (BHJ) composed of PBDB-T and PC71BM, is employed to simultaneously realize vertical electron and hole transports through the separate p-channel and n-channel. The gate-modulated graphene work functions enable broad modulation of SB heights at both the graphene-PBDB-T and graphene-PC71BM heterointerfaces. Interestingly, the fine-tuned energy-level alignment enables an exclusive injection of holes or electrons unlike conventional BHJ-based ambipolar transistors, leading to a clear transition between p-channel and n-channel single-carrier-like transistor characteristics. Furthermore, the improved percolation-limited dual charge transport in vertical architecture results in high charge carrier density and high-speed on-off switching characteristics, providing a high on-off current ratio exceeding 105 and an operation speed of 100 kHz. Solution-based on-substrate fabrications of low-power complementary logic gates such as NOT, NOR, and NAND are also successfully performed.

Organic-inorganic hybrid perovskite electronics.

Organic-inorganic hybrid perovskite is a leading successor for the next generation of electronic and optoelectronic applications, owing to its unique optical and electrical properties. In this perspective, tunable optical and electrical properties are discussed, based on the nanostructured morphologies of hybrid perovskites. The current methodologies used in creating semiconducting channels are highlighted, followed by a detailed discussion of the recent advances in unique electronics and optoelectronic applications such as light-emitting transistors, phototransistors, and perovskite-2D hybrid devices. Finally, the current technological challenges and their possible solutions are addressed to identify future research directions.

Correlation between electrical properties and cation distribution in [(Ni x Mn1- x )0.84Cu0.16]3O4 thin films prepared by metal-organic decomposition for microbolometer applications.

[(Nix Mn 1- x )0.84Cu 0.16]3O4 (0.20 ≤ x ≤ 0.40) thin films have been prepared using the metal-organic decomposition method for microbolometer applications. Spinel thin films with a thickness of approximately 100 nm were obtained from the [(Ni x Mn1- x )0.84Cu0.16]3O4 films annealed at the low temperature of 380 °C for 5 h, which enables their direct integration onto substrates having complementary metal-oxide-semiconductor (CMOS) read-out circuitry. To obtain negative-temperature-coefficient films with reasonable performance through low enough temperature anneal process, Ni content has been systematically varied, and the film microstructure has been found to depend on the relative amount of Ni and Mn. A single phase of cubic spinel structure has been confirmed in the prepared films. The resistivity (ρ) of the annealed films decreases with increasing Mn4+/Mn3+ value due to the hopping mechanism between Mn3+ and Mn4+ cations in octahedral sites of spinel structure. Although the temperature coefficient of resistance (TCR) of the annealed films has been decreased slightly with the increase of Ni content, good enough properties of the film (ρ = 61.3 Ω•cm, TCR = -2.950%/K in x = 0.30 film) has been obtained even with the annealing at rather low temperature of 380 °C, thus enabling the direct integration onto substrates having read-out circuitry. The results obtained in this work are promising for applications to CMOS integrated microbolometer devices.

Generalized Scheme for High Performing Photodetectors with a p-Type 2D Channel Layer and n-Type Nanoparticles.

A generalized scheme for the fabrication of high performance photodetectors consisting of a p-type channel material and n-type nanoparticles is proposed. The high performance of the proposed hybrid photodetector is achieved through enhanced photoabsorption and the photocurrent gain arising from its effective charge transfer mechanism. In this paper, the realization of this design is presented in a hybrid photodetector consisting of 2D p-type black phosphorus (BP) and n-type molybdenum disulfide nanoparticles (MoS2 NPs), and it is demonstrated that it exhibits enhanced photoresponsivity and detectivity compared to pristine BP photodetectors. It is found that the performance of hybrid photodetector depends on the density of NPs on BP layer and that the response time can be reduced with increasing density of MoS2 NPs. The rising and falling times of this photodetector are smaller than those of BP photodetectors without NPs. This proposed scheme is expected to work equally well for a photodetector with an n-type channel material and p-type nanoparticles.

Large-Area CVD-Grown Sub-2 V ReS2 Transistors and Logic Gates.

We demonstrated the fabrication of large-area ReS2 transistors and logic gates composed of a chemical vapor deposition (CVD)-grown multilayer ReS2 semiconductor channel and graphene electrodes. Single-layer graphene was used as the source/drain and coplanar gate electrodes. An ion gel with an ultrahigh capacitance effectively gated the ReS2 channel at a low voltage, below 2 V, through a coplanar gate. The contact resistance of the ion gel-gated ReS2 transistors with graphene electrodes decreased dramatically compared with the SiO2-devices prepared with Cr electrodes. The resulting transistors exhibited good device performances, including a maximum electron mobility of 0.9 cm2/(V s) and an on/off current ratio exceeding 104. NMOS logic devices, such as NOT, NAND, and NOR gates, were assembled using the resulting transistors as a proof of concept demonstration of the applicability of the devices to complex logic circuits. The large-area synthesis of ReS2 semiconductors and graphene electrodes and their applications in logic devices open up new opportunities for realizing future flexible electronics based on 2D nanomaterials.

Probing Out-of-Plane Charge Transport in Black Phosphorus with Graphene-Contacted Vertical Field-Effect Transistors.

Black phosphorus (BP) has recently emerged as a promising narrow band gap layered semiconductor with optoelectronic properties that bridge the gap between semimetallic graphene and wide band gap transition metal dichalcogenides such as MoS2. To date, BP field-effect transistors have utilized a lateral geometry with in-plane transport dominating device characteristics. In contrast, we present here a vertical field-effect transistor geometry based on a graphene/BP van der Waals heterostructure. The resulting device characteristics include high on-state current densities (>1600 A/cm(2)) and current on/off ratios exceeding 800 at low temperature. Two distinct charge transport mechanisms are identified, which are dominant for different regimes of temperature and gate voltage. In particular, the Schottky barrier between graphene and BP determines charge transport at high temperatures and positive gate voltages, whereas tunneling dominates at low temperatures and negative gate voltages. These results elucidate out-of-plane electronic transport in BP and thus have implications for the design and operation of BP-based van der Waals heterostructures.

Multifunctional graphene optoelectronic devices capable of detecting and storing photonic signals.

The advantages of graphene photodetectors were utilized to design a new multifunctional graphene optoelectronic device. Organic semiconductors, gold nanoparticles (AuNPs), and graphene were combined to fabricate a photodetecting device with a nonvolatile memory function for storing photonic signals. A pentacene organic semiconductor acted as a light absorption layer in the device and provided a high hole photocurrent to the graphene channel. The AuNPs, positioned between the tunneling and blocking dielectric layers, acted as both a charge trap layer and a plasmonic light scatterer, which enable storing of the information about the incident light. The proposed pentacene-graphene-AuNP hybrid photodetector not only performed well as a photodetector in the visible light range, it also was able to store the photonic signal in the form of persistent current. The good photodetection performance resulted from the plasmonics-enabled enhancement of the optical absorption and from the photogating mechanisms in the pentacene. The device provided a photoresponse that depended on the wavelength of incident light; therefore, the signal information (both the wavelength and intensity) of the incident light was effectively committed to memory. The simple process of applying a negative pulse gate voltage could then erase the programmed information. The proposed photodetector with the capacity to store a photonic signal in memory represents a significant step toward the use of graphene in optoelectronic devices.

Graphene-graphene oxide floating gate transistor memory.

A novel transparent, flexible, graphene channel floating-gate transistor memory (FGTM) device is fabricated using a graphene oxide (GO) charge trapping layer on a plastic substrate. The GO layer, which bears ammonium groups (NH3+), is prepared at the interface between the crosslinked PVP (cPVP) tunneling dielectric and the Al2 O3 blocking dielectric layers. Important design rules are proposed for a high-performance graphene memory device: (i) precise doping of the graphene channel, and (ii) chemical functionalization of the GO charge trapping layer. How to control memory characteristics by graphene doping is systematically explained, and the optimal conditions for the best performance of the memory devices are found. Note that precise control over the doping of the graphene channel maximizes the conductance difference at a zero gate voltage, which reduces the device power consumption. The proposed optimization via graphene doping can be applied to any graphene channel transistor-type memory device. Additionally, the positively charged GO (GO-NH3+) interacts electrostatically with hydroxyl groups of both UV-treated Al2 O3 and PVP layers, which enhances the interfacial adhesion, and thus the mechanical stability of the device during bending. The resulting graphene-graphene oxide FGTMs exhibit excellent memory characteristics, including a large memory window (11.7 V), fast switching speed (1 µs), cyclic endurance (200 cycles), stable retention (10(5) s), and good mechanical stability (1000 cycles).

X-DNA origami-networked core-supported lipid stratum.

DNA hydrogels are promising materials for various fields of research, such as in vitro protein production, drug carrier systems, and cell transplantation. For effective application and further utilization of DNA hydrogels, highly effective methods of nano- and microscale DNA hydrogel fabrication are needed. In this respect, the fundamental advantages of a core-shell structure can provide a simple remedy. An isolated reaction chamber and massive production platform can be provided by a core-shell structure, and lipids are one of the best shell precursor candidates because of their intrinsic biocompatibility and potential for easy modification. Here, we demonstrate a novel core-shell nanostructure made of gene-knitted X-shaped DNA (X-DNA) origami-networked gel core-supported lipid strata. It was simply organized by cross-linking DNA molecules via T4 enzymatic ligation and enclosing them in lipid strata. As a condensed core structure, the DNA gel shows Brownian behavior in a confined area. It has been speculated that they could, in the future, be utilized for in vitro protein synthesis, gene-integration transporters, and even new molecular bottom-up biological machineries.

Observation of the inverse giant piezoresistance effect in silicon nanomembranes probed by ultrafast terahertz spectroscopy.

The anomalous piezoresistance (a-PZR) effects, including giant PZR (GPZR) with large magnitude and inverse PZR of opposite, have exciting technological potentials for their integration into novel nanoelectromechanical systems. However, the nature of a-PZR effect and the associated kinetics have not been clearly determined yet. Even further, there are intense research debates whether the a-PZR effect actually exists or not; although numerous investigations have been conducted, the origin of the effect has not been clearly understood. This paper shows the existence of a-PZR and provides direct experimental evidence through the performance of well-established electrical measurements and terahertz spectroscopy on silicon nanomembranes (Si NMs). The clear inverse PZR behavior was observed in the Si NMs when the thickness was less than 40 nm and the magnitude of the PZR response linearly increased with the decreasing thickness. Observations combined with electrical and optical measurements strongly corroborate that the a-PZR effect originates from the carrier concentration changes via charge carrier trapping into strain-induced defect states.

Water-gel for gating graphene transistors.

Water, the primary electrolyte in biology, attracts significant interest as an electrolyte-type dielectric material for transistors compatible with biological systems. Unfortunately, the fluidic nature and low ionic conductivity of water prevents its practical usage in such applications. Here, we describe the development of a solid state, megahertz-operating, water-based gate dielectric system for operating graphene transistors. The new electrolyte systems were prepared by dissolving metal-substituted DNA polyelectrolytes into water. The addition of these biocompatible polyelectrolytes induced hydrogelation to provide solid-state integrity to the system. They also enhanced the ionic conductivities of the electrolytes, which in turn led to the quick formation of an electric double layer at the graphene/electrolyte interface that is beneficial for modulating currents in graphene transistors at high frequencies. At the optimized conditions, the Na-DNA water-gel-gated flexible transistors and inverters were operated at frequencies above 1 MHz and 100 kHz, respectively.

Transistor memory devices with large memory windows, using multi-stacking of densely packed, hydrophobic charge trapping metal nanoparticle array.

Organic field-effect transistor (OFET) memories have rapidly evolved from low-cost and flexible electronics with relatively low-memory capacities to memory devices that require high-capacity memory such as smart memory cards or solid-state hard drives. Here, we report the high-capacity OFET memories based on the multilayer stacking of densely packed hydrophobic metal NP layers in place of the traditional transistor memory systems based on a single charge trapping layer. We demonstrated that the memory performances of devices could be significantly enhanced by controlling the adsorption isotherm behavior, multilayer stacking structure and hydrophobicity of the metal NPs. For this study, tetraoctylammonium (TOA)-stabilized Au nanoparticles (TOA-Au(NPs)) were consecutively layer-by-layer (LbL) assembled with an amine-functionalized poly(amidoamine) dendrimer (PAD). The formed (PAD/TOA-Au(NP))(n) films were used as a multilayer stacked charge trapping layer at the interface between the tunneling dielectric layer and the SiO2 gate dielectric layer. For a single AuNP layer (i.e. PAD/TOA-Au(NP))1) with a number density of 1.82 × 10(12) cm(-2), the memory window of the OFET memory device was measured to be approximately 97 V. The multilayer stacked OFET memory devices prepared with four Au(NP) layers exhibited excellent programmable memory properties (i.e. a large memory window (ΔV(th)) exceeding 145 V, a fast switching speed (1 µs), a high program/erase (P/E) current ratio (greater than 10(6)) and good electrical reliability) during writing and erasing over a relatively short time scale under an operation voltage of 100 V applied at the gate.

Photo-patternable ion gel-gated graphene transistors and inverters on plastic.

We demonstrate photo-patternable ion gel-gated graphene transistors and inverters on plastic substrates. The photo-patternable ion gel can be used as a negative photoresist for the patterning of underlying graphene as well as gate dielectrics. As a result, an extra graphene-patterning step is not required, which simplifies the device fabrication and avoids a side effect arising from the photoresist residue. The high capacitance of ion gel gate dielectrics yielded a low voltage operation (~2 V) of the graphene transistor and inverter. The graphene transistors on plastic showed an on/off-current ratio of ~11.5, along with hole and electron mobilities of 852 ± 124 and 452 ± 98 cm(2) V(-1) s(-1), respectively. In addition, the flexible graphene inverter was successfully fabricated on plastic through the potential superposition effect from the drain bias. These devices show excellent mechanical flexibility and fatigue stability.

Quantum confinement effects in transferrable silicon nanomembranes and their applications on unusual substrates.

Two dimensional (2D) semiconductors have attracted attention for a range of electronic applications, such as transparent, flexible field effect transistors and sensors owing to their good optical transparency and mechanical flexibility. Efforts to exploit 2D semiconductors in electronics are hampered, however, by the lack of efficient methods for their synthesis at levels of quality, uniformity, and reliability needed for practical applications. Here, as an alternative 2D semiconductor, we study single crystal Si nanomembranes (NMs), formed in large area sheets with precisely defined thicknesses ranging from 1.4 to 10 nm. These Si NMs exhibit electronic properties of two-dimensional quantum wells and offer exceptionally high optical transparency and low flexural rigidity. Deterministic assembly techniques allow integration of these materials into unusual device architectures, including field effect transistors with total thicknesses of less than 12 nm, for potential use in transparent, flexible, and stretchable forms of electronics.

Tailoring Three-Dimensional Cross-Linked Networks Based on Water-Soluble Polymeric Materials for Stable Silicon Anode.

For stable battery operation of silicon (Si)-based anodes, utilizing cross-linked three-dimensional (3D) network binders has emerged as an effective strategy to mitigate significant volume fluctuations of Si particles. In the design of cross-linked network binders, careful selection of appropriate cross-linking agents is crucial to maintaining a balance between the robustness and functionality of the network. Herein, we strategically design and optimize a 3D cross-linked network binder through a comprehensive analysis of cross-linking agents. The proposed network is composed of poly(vinyl alcohol) grafted poly(acrylic acid) (PVA-g-PAA, PVgA) and aromatic diamines. PVgA is chosen as the polymer backbone owing to its high flexibility and facile synthesis using an ecofriendly water solvent. Subsequently, an aromatic diamine is employed as a cross-linker to construct a robust amide network that features a resonance-stabilized high modulus and enhanced adhesion. Comparative investigations of three cross-linkers, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-oxidianiline, and 4,4'-oxybis[3-(trifluoromethyl)aniline] (TFODA), highlight the roles of the trifluoromethyl group (-CF3) and the ether linkage. Consequently, PVgA cross-linked with TFODA (PVgA-TFODA), featuring both -CF3 and -O-, establishes a well-balanced 3D network characterized by heightened elasticity and improved binding forces. The optimized Si and SiOx/graphite composite electrodes with the PVgA-TFODA binder demonstrate impressive structural stability and stable cycling. This study offers a novel perspective on designing cross-linked network binders, showcasing the benefits of a multidimensional approach considering chemical and physical interactions.

Toward human-like adaptability in robotics through a retention-engineered synaptic control system.

Although advanced robots can adeptly mimic human movement and aesthetics, they are still unable to adapt or evolve in response to external experiences. To address this limitation, we propose an innovative approach that uses parallel-processable retention-engineered synaptic devices in the control system. This approach aims to simulate a human-like learning system without necessitating complex computational systems. The retention properties of the synaptic devices were modulated by adjusting the amount of Ag/AgCl ink sprayed. This changed the voltage drop across the interface between the gate electrode and the electrolyte. Furthermore, the unrestricted movement of ions in the electrolyte enhanced the signal multiplexing capability of the ion gel, enabling device-level parallel processing. By integrating the unique characteristics of the synaptic devices with actuators, we successfully emulated a human-like workout process that includes feedback between acute and chronic responses. The proposed control system offers an innovative approach to reducing system complexity and achieving a human-like learning system in the field of biomimicry.