Chiroptical‐Conjugated Polymer/Chiral Small Molecule Hybrid Thin Films for Circularly Polarized Light‐Detecting Heterojunction Devices

Herein, a simple and facile strategy is described to obtain chiroptically active semiconductor thin films by blending of poly(3‐alkylthiophene)s, which are conventional achiral polymer semiconductors, and 1,1′‐binaphthyl (BN), a versatile chiral molecule. As expected, the intermolecular interaction between the two materials is important to extend the chirality of the binaphthyl molecules to the hybrid films. The controlled phase separation and crystallization of poly[3‐(6‐carboxyhexyl)thiophene‐2,5‐diyl] (P3CT) and binaphthyl hybrid films result in unique heterojunction bilayer thin‐film structures that consisted of BN microcrystals at the top and a P3CT/BN mixed layer at the bottom. Such heterojunction bilayer films exhibit significantly amplified chiroptical response with weak broadened tails, which is due to the enhanced crystallization of the chiral BN molecules and formation of heteroaggregates in the hybrid films. Based on the characterization of crystalline structure and photoluminescence analysis, it is found that new electronic energy states are formed in the conduction band region of P3CTs in the P3CT/BN heteroaggregates, which contribute to chirality transfer from BN to the hybrid films. As a proof of concept, a photodiode capable of distinguishably sensing the left‐ and right‐handed circularly polarized light is successfully fabricated by using the hybrid films with the heterojunction bilayer structure.     

Complexity‐Reduced Algorithms for LDPC Decoder for DVB‐S2 Systems

This paper proposes two kinds of complexity‐reduced algorithms for a low density parity check(LDPC) decoder. First, sequential decoding using a partial group is proposed. It has the same hardware complexity and requires a fewer number of iterations with little performance loss. The amount of performance loss can be determined by the designer, based on a tradeoff with the desired reduction in complexity. Second, an early detection method for reducing the computational complexity is proposed. Using a confidence criterion, some bit nodes and check node edges are detected early on during decoding. Once the edges are detected, no further iteration is required; thus early detection reduces the computational complexity.     

Near‐Optimum Blind Decision Feedback Equalization for ATSC Digital Television Receivers

This paper presents a near‐optimum blind decision feedback equalizer (DFE) for the receivers of Advanced Television Systems Committee (ATSC) digital television. By adopting a modified trellis decoder (MTD) with a trace‐ back depth of 1 for the decision device in the DFE, we obtain a hardware‐efficient, blind DFE approaching the performance of an optimum DFE which has no error propagation. In the MTD, the absolute distance is used rather than the squared Euclidean distance for the computation of the branch metrics. This results in a reduction of the computational complexity over the original trellis decoding scheme. Compared to the conventional slicer, the MTD shows an outstanding performance improvement in decision error probability and is comparable to the original trellis decoder using the Euclidean distance. Reducing error propagation by use of the MTD in the DFE leads to the improvement of convergence performance in terms of convergence speed and residual error. Simulation results show that the proposed blind DFE performs much better than the blind DFE with the slicer, and the difference is prominent at the trellis decoder following the blind DFE.     

Back channel etch chemistry of advanced a-Si:H TFTs

We report on the effects of back channel etch depth and etchant chemistry on the electrical characteristics of inverted staggered advanced amorphous silicon thin-film transistors. We found that the optimum amorphous silicon film thickness in the channel is about 800-1100 Å. Three dry etch, HBr + Cl₂, C₂F₆, and CCl₂F₂ + O₂, and one wet etch, KOH, chemistries are used for the back channel etch processing. We established that dry etch can be used for the back channel etch of amorphous silicon transistor without degrading its electrical characteristics.     

Metallic Nanowire Coupled CsPbBr3 Quantum Dots Plasmonic Nanolaser

Plasmonic nanolasers provide a valuable opportunity for expanding sub-wavelength applications. Due to the potential of on-chip integration, semiconductor nanowire (NW)-based plasmonic nanolasers that support the waveguide mode attract a high level of interest. To date, perovskite quantum dots (QDs) based plasmonic lasers, especially nanolasers that support plasmonic-waveguide mode, are still a challenge and remain unexplored. Here, metallic NW coupled CsPbBr₃ QDs plasmonic-waveguide lasers are reported. By embedding Ag NWs in QDs film, an evolution from amplified spontaneous emission with a full width at half maximum (FWHM) of 6.6 nm to localized surface plasmon resonance (LSPR) supported random lasing is observed. When the pump light is focused on a single Ag NW, a QD-NW coupled plasmonic-waveguide laser with a much narrower emission peak (FWHM = 0.4 nm) is realized on a single Ag NW with the uniform polyvinylpyrrolidone layer. The QDs serve as the gain medium while the Ag NW serves as a resonant cavity and propagating plasmonic lasing modes. Furthermore, by pumping two Ag NWs with different directions, a dual-wavelength lasing switch is realized. The demonstration of metallic NW coupled QDs plasmonic nanolaser would provide an alternative approach for ultrasmall light sources as well as fundamental studies of light matter interactions.     

Anomaly detection in particulate matter sensor using hypothesis pruning generative adversarial network

The World Health Organization provides guidelines for managing the particulate matter (PM) level because a higher PM level represents a threat to human health. To manage the PM level, a procedure for measuring the PM value is first needed. We use a PM sensor that collects the PM level by laser-based light scattering (LLS) method because it is more cost effective than a beta attenuation monitor-based sensor or tapered element oscillating microbalance-based sensor. However, an LLS-based sensor has a higher probability of malfunctioning than the higher cost sensors. In this paper, we regard the overall malfunctioning, including strange value collection or missing collection data as anomalies, and we aim to detect anomalies for the maintenance of PM measuring sensors. We propose a novel architecture for solving the above aim that we call the hypothesis pruning generative adversarial network (HP-GAN). Through comparative experiments, we achieve AUROC and AUPRC values of 0.948 and 0.967, respectively, in the detection of anomalies in LLS-based PM measuring sensors. We conclude that our HP-GAN is a cutting-edge model for anomaly detection.     

Mitigation and Verification Methods for Sn Whisker Growth in Pb-Free Automotive Electronics

This work describes mitigation methods against Sn whisker growth in Pb-free automotive electronics using a conformal coating technique, with an additional focus on determining an effective whisker assessment method. We suggest effective whisker growth conditions that involve temperature cycling and two types of storage conditions (high-temperature/humidity storage and ambient storage), and analyze whisker growth mechanisms. In determining an efficient mitigation method against whisker growth, surface finish and conformal coating have been validated as effective means. In our experiments, the surface finish of components comprised Ni/Sn, Ni/SnBi, and Ni/Pd. The effects of acrylic silicone, and rubber coating of components were compared with uncoated performance under high-temperature/humidity storage conditions. An effective whisker assessment method during temperature cycling and under various storage conditions (high temperature/humidity and ambient) is indicated for evaluating whisker growth. Although components were finished with Ni/Pd, we found that whiskers were generated at solder joints and that conformal coating is a useful mitigation method in this regard. Although whiskers penetrated most conformal coating materials (acrylic, silicone, and rubber) after 3500 h of high-temperature/humidity storage, the whisker length was markedly reduced due to the conformal coatings, with silicone providing superior mitigation over acrylic and rubber.     

High‐Mobility n‐Type Organic Transistors Based on a Crystallized Diketopyrrolopyrrole Derivative

A new high‐performing small molecule n‐channel semiconductor based on diketopyrrolopyrrole (DPP), 2,2′‐(5,5′‐(2,5‐bis(2‐ethylhexyl)‐3,6‐dioxo‐2,3,5,6‐tetrahydropyrrolo[3,4‐c]pyrrole‐1,4‐diyl)bis(thiophene‐5,2‐diyl))bis(methan‐1‐yl‐1‐ylidene)dimalononitrile (DPP‐T‐DCV), is successfully synthesized. The frontier molecular orbitals in this designed structure are elaborately tuned by introducing a strong electron‐accepting functionality (dicyanovinyl). The well‐defined lamellar structures of the crystals display a uniform terrace step height corresponding to a molecular monolayer in the solid‐state. As a result of this tuning and the remarkable crystallinity derived from the conformational planarity, organic field‐effect transistors (OFETs) based on dense‐packed solution‐processed single‐crystals of DPP‐T‐DCV exhibit an electron mobility (μ_e) up to 0.96 cm² V^?1 s^?1, one of the highest values yet obtained for DPP derivative‐based n‐channel OFETs. Polycrystalline OFETs show promise (with an μ_e up to 0.64 cm² V^?1 s^?1) for practical utility in organic device applications.     

Fabrication of Superjunction Trench Gate Power MOSFETs Using BSG‐Doped Deep Trench of p‐Pillar

In this paper, we propose a superjunction trench gate MOSFET (SJ TGMOSFET) fabricated through a simple p pillar forming process using deep trench and boron silicate glass doping process technology to reduce the process complexity. Throughout the various boron doping experiments, as well as the process simulations, we optimize the process conditions related with the p pillar depth, lateral boron doping concentration, and diffusion temperature. Compared with a conventional TGMOSFET, the potential of the SJ TGMOSFET is more uniformly distributed and widely spread in the bulk region of the n drift layer due to the trenched p‐pillar. The measured breakdown voltage of the SJ TGMOSFET is at least 28% more than that of a conventional device.