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Recently, organic-inorganic halide perovskite (OHP) has been suggested as an alternative to oxides or chalcogenides in resistive switching memory devices due to low operating voltage, high ON/OFF ratio, and flexibility. The most studied OHP is 3-dimensional (3D) MAPbI(3). However, MAPbI(3) often exhibits less reliable switching behavior probably due to the uncontrollable random formation of conducting filaments. Here, we report the resistive switching property of 2-dimensional (2D) OHP and compare switching characteristics depending on structural dimensionality. The dimensionality is controlled by changing the composition of BA(2)MA(n-1)PbnI(3n+1) (BA = butylammonium, MA = methylammonium), where 2D is formed from n = 1, and 3D is formed from n = infinity. Quasi 2D compositions with n = 2 and 3 are also compared. Transition from a high resistance state (HRS) to a low resistance state (LRS) occurs at 0.25 x 10(6) V m(-1) for 2D BA(2)PbI(4) film, which is lower than those for quasi 2D and 3D. Upon reducing the dimensionality from 3D to 2D, the ON/OFF ratio significantly increases from 10(2) to 10(7), which is mainly due to the decreased HRS current. A higher Schottky barrier and thermal activation energy are responsible for the low HRS current. We demonstrate for the first time reliable resistive switching from 4 inch wafer-scale BA(2)PbI(4) thin film working at both room temperature and a high temperature of 87 degrees C, which strongly suggests that 2D OHP is a promising candidate for resistive switching memory.

We prepared high performance metal nanowire (NW)-parylene C transparent electrodes (TEs) using pyrolytic deposition of a parylene C protection layer onto a silver nanowire (AgNW) or copper nanowire (CuNW) film at room temperature for the first time. The AgNW-parylene C TE showed superior optoelectronic properties such as high optical transmittance (94.7%) and low sheet resistance (41.6 Ω sq−1), comparable to a conventional indium tin oxide (ITO) TE. The AgNW-parylene C TE fabricated on a plastic substrate possessed outstanding flexibility. Moreover, the AgNW-parylene C and CuNW-parylene C TEs exhibited significantly improved oxidation and chemical stability due to the outstanding gas barrier properties of the parylene C protection layer. Furthermore, the potential suitability of the AgNW-parylene C TE was successfully demonstrated by fabricating flexible polymer solar cells. We expect that the flexible metal NW-parylene C TEs can be used as key elements for a variety of next generation optoelectronic devices.

Chemoresistive gas sensors based on two-dimensional (2D) materials including graphene-based materials have attracted significant research interest owing to their potential use in next-generation technologies including the Internet of Things (IoT). The functionalization of 2D materials is considered as a key strategy to achieve superior gas sensing properties such as high selectivity, high sensitivity, and reversible response and recovery, because it can modulate the chemical and electrical properties of 2D materials for more efficient gas sensing. Herein, we present a facile solution process and the room temperature gas sensing properties of chemically fluorinated graphene oxide (CFGO). The CFGO sensors exhibit improved sensitivity, selectivity, and reversibility upon exposure to NH3 with a significantly low theoretical detection limit of ∼6 ppb at room temperature in comparison to NO2 sensing properties. The effect of fluorine doping on the sensing mechanism is examined by first-principles calculations based on density functional theory. The calculations reveal that the fluorine dopant changes the charge distribution on the oxygen containing functional groups in graphene oxide, resulting in the preferred selective adsorption and desorption of NH3 molecules. We believe that the remarkable NH3 sensing properties of CFGO and investigation by first-principles calculations would enlarge the possibility of functionalized 2D materials for practical gas sensing applications such as the IoT.

Hydrogen spillover is a catalytic process that occurs by surface reaction and subsequent diffusion to reversibly provide a massive amount of hydrogen dopants in correlated oxides, but the mechanism at the surface of correlated oxides with metal catalyst are not well understood. Here we show that a significant amount of oxygen is released from the surface of correlated VO2 films during hydrogen spillover, contrary to the well-established observation of the formation of hydrogen interstitials in the bulk part of VO2 films. By using ambient-pressure X-ray photoelectron spectroscopy, we prove that the formation of surface oxygen vacancies is a consequence of a favorable reaction for the generation of weakly adsorbed H2O from surface O atoms that have low coordination and weak binding strength. Our results reveal the importance of in situ characterization to prove the dynamic change during redox reaction and present an opportunity to control intrinsic defects at the surface.

Effective temperature measurement using non-invasive sensors finds applications in virtually every field of human life. Recently, significant efforts have been made toward developing polymer positive temperature coefficient (PTC) thermistors because they have advantages including flexibility, conformability, and biocompatibility. However, most polymer PTC thermistors still have issues such as low sensitivity, low optical transparency, and poor operational durability because of low electrical conductivity and inefficient hopping transport of conventional conductive filler. Here, a highly sensitive and transparent polymer thermistor composed of silver fractal dendrites (AgFDs) and a polyacrylate (PA) matrix has been successfully demonstrated. A AgFDs-PA composite film exhibits a superior PTC effect (about 104Ω°C-1) around 35 °C because of the high electrical conductivity of the AgFDs and the quantum tunneling effect among them. A thermistor based on the AgFDs-PA composite shows excellent sensitivity, PTC intensity (∼107), and sensing resolution through dramatic resistance changes from thousands to billions of ohms in the human body temperature range (34-37 °C). Moreover, it exhibits excellent optical transparency (82.14%), mechanical flexibility, and operational durability. An electrical impedance spectroscopy analysis shows that the distance between the AgFDs increases with temperature, which implies that the quantum tunneling effect amplified by the branches of the AgFDs has a significant influence on the changes in resistance. This characteristic makes the thermistor immediately suitable for monitoring body temperature. We anticipate that the new thermistor based on the AgFDs-PA composite can be a key component of various sensing applications.

People use their hands the most to interact with computers. However, there are many inherent problems with the methods used for hand detection. Various shapes of hands, complex backgrounds and illumination can induce much misdetection. To use hands to interact with a computer, it is very important to have a robust hand area. Therefore, this paper proposes a method of acquiring a robust hand area in various environments. The proposed system operates in real-time and has good performance in environments of various illuminations and complex backgrounds.

Graphene is one of the most promising materials for high-performance gas sensors due to its unique properties such as high sensitivity at room temperature, transparency, and flexibility. However, the low selectivity and irreversible behavior of graphene-based gas sensors are major problems. Here, we present unprecedented room temperature hydrogen detection by Au nanoclusters supported on self-activated graphene. Compared to pristine graphene sensors, the Au-decorated graphene sensors exhibit highly improved gas-sensing properties upon exposure to various gases. In particular, an unexpected substantial enhancement in H2 detection is found, which has never been reported for Au decoration on any type of chemoresistive material. Density functional theory calculations reveal that Au nanoclusters on graphene contribute to the adsorption of H atoms, whereas the surfaces of Au and graphene do not bind with H atoms individually. The discovery of such a new functionality in the existing material platform holds the key to diverse research areas based on metal nanocluster/graphene heterostructures.

All-inorganic cesium lead triiodide (CsPbI

We present a compact fiber-optic pressure sensor based on a long period fiber grating with the short length of ~1.8 cm (33 grating periods). The grating is induced in a two-mode fiber as a form of periodic micro-bends by an externally tunable inter-modal converter.

We successfully combined electrothermal and phase-field models in a finite element framework to establish a device model for set operation in phase-change memory. The electrothermal model calculates current density, Joule heating and heat transfer, and the resulting temperature profile from bias conditions while the phase-field model calculates thermal history dependent phase-change such as melt-quench and stochastic nucleation followed by growth. In this work, we will discuss capabilities of our model and its applications to set pulse design and intrinsic variability analysis.

One of the well-known pathways toward low power consuming chemoresistive gas sensors is the utilization of 2-dimensional materials. Especially, transition metal dichalcogenides (TMDs), which are usually atomically thin semiconductors, have a notable characteristic of their highly reactive edge sites. The edge sites of TMDs having high d-orbital electron density can serve as highly favorable chemically active sites for direct interaction with target gas molecules. In this study, WS2 was synthesized on highly porous SiO2 nanorods template to have numerous edge-exposed WS2 flakes in a limited active area taking advantage of 1-dimensional nanostructures with extremely high surface-to-volume ratio. The fabricated WS2 on 1D nanostructures exhibited a gas response of 151.2 % toward 5 ppm NO2, which has not been reported in performance-wise at room temperature to the best of the author’s knowledge. Density functional theory calculations theoretically supported the highly sensitive and selective NO2 detection with a theoretical detection limit of 13.726 ppb.

An understanding of the phase transition in organic-inorganic hybrid perovskites is quite important. These phase transitions have been widely studied as they induce differences in structural, electronic, and optical properties. Thermochromic perovskite materials, which alter their optical bandgap in response to a change in temperature, have shown their potential in smart photovoltaic window applications by utilizing the structural phase transitions of inorganic halide perovskites. Here, we investigated the thermochromic properties of guanidinium (C(NH2)3) lead triiodide (GAPbI3) which shows a reversible crystallographic phase transition between a transparent orthorhombic phase (Pna21) ( 3 ¯ m) (>160 °C). The thermal behavior, crystallographic information, and optical and electronic properties of GAPbI3 in these two phases were also investigated. We are the first to report that an atomic layer deposition (ALD)-grown SnO2 passivation layer deposited on top of the perovskite layer can successfully stabilize trigonal-phase of GAPbI3 for 14 h. Furthermore, in the GAPbI3 photodetector device, the on/off photoswitching property was greatly enhanced through thermochromism.

We investigated the high-purity entangled photon-pair generation in five kinds of &ldquo, non-poled&rdquo, potassium titanyl phosphate (KTP) isomorphs (i.e., KTiOPO4, RbTiOPO4, KTiOAsO4, RbTiOAsO4, and CsTiOAsO4). The technique is based on the spontaneous parametric down-conversion (SPDC) under Type II extended phase matching (EPM), where the phase matching and the group velocity matching are simultaneously achieved between the interacting photons in non-poled crystals rather than periodically poled (PP) KTPs that are widely used for quantum experiments. We discussed both theoretically and numerically all aspects required to generate photon pairs in non-poled KTP isomorphs, in terms of the range of the beam propagation direction (or the spectral range of photons) and the corresponding effective nonlinearities and beam walk-offs. We showed that the SPDC efficiency can be increased in non-poled KTP isomorphs by 29% to 77% compared to PPKTP cases. The joint spectral analyses showed that photon pairs can be generated with high purities of 0.995&ndash, 0.997 with proper pump filtering. In contrast to the PPKTP case, where the EPM is achieved only at one specific wavelength, the spectral position of photon pairs in the non-poled KTP isomorphs can be chosen over the wide range of 1883.8&ndash, 2068.1 nm.

We investigate the high-purity entangled photon pair generation in a recently developed borate crystal, Ba3Mg3(BO3)3F3. The technique is based on the spontaneous parametric down-conversion under the extended phase matching (EPM), where the phase matching and the group velocity matching between the interacting photons are satisfied simultaneously in bulk crystals with point symmetry of orthorhombic mm2 (thus showing biaxial birefringence). We will discuss all the theoretical aspects required for the generation of photon pairs in mm2 biaxial crystals, which are much more complex than the cases of uniaxial crystals (e.g., &beta, BaB2O4 and LiNbO3) and periodically poled crystals that are widely used in the field. Our study includes theoretical and numerical investigations of two types of EPM and their corresponding effective nonlinearities and spatial walk-offs. The results show that two types of EPM are satisfied over the specific range in the direction of pump wave vector, corresponding to its spectral ranges of 876.15&ndash, 1052.77 nm for Type I and 883.92&ndash, 914.33 nm for Type II. The joint spectral analyses show that photon-pairs can be generated with high purities of 0.997 with a proper pump filtering (for Type II), and 0.833 even without pump filtering (for Type I).

Nanostructured catalysts have been extensively demonstrated for electrochemical CO2 reduction. But, efforts to understand the mechanism of bimetallic catalysts have been limited. Here, we study electronic structures in bimetallic Cu/Ag layered catalysts to eliminate geometrical effects on the electrocatalytic characteristics. We found that the interfacial interaction between Cu and Ag affects the valence electronic states as confirmed by synchrotron radiation photoelectron spectroscopy and density functional theory calculation. The Ag adatom on Cu surface decreases charge density by forming an additional bond with Cu. As a result, the binding energy of CO intermediate increases on the surface. As the thickness of Ag layer increases, the effect of interfacial interaction of Cu/Ag gradually weakened and the center of d-states downshifted from 4.38 to 5.28 eV. The optimized Cu/Ag layered catalyst exhibited bifunctional catalytic selectivity with high CO faradaic efficiency (FE) = 89.1% at −0.8 VRHE and high methane FE = 65.3% at −1.2 VRHE.

A single-phase face-centered-cubic (FCC) high- or medium-entropy alloys (HEAs or MEAs) have attracted great attentions due to their novel damage-tolerance properties (strength, ductility, and fracture toughness) by generating nano-twins at cryogenic temperature. The fracture toughness assessment is essential for evaluating the reliability of high-performance materials for cryogenic applications; however, fracture studies on single-phase FCC HEAs showing transformation-induced plasticity (TRIP) have been hardly conducted. In this study, thus, damage-tolerance mechanisms of a V10Cr10Fe45Co30Ni5 HEA showing the FCC to body-centered-cubic (BCC) TRIP were investigated at room and cryogenic temperatures. At room temperature (298 K), the alloy shows the tensile strength of 731 MPa, elongation of 40%, and fracture toughness (KJIc) of 230 MPa m1/2. At cryogenic temperature (77 K), the strength and elongation improve to 1.2 GPa and 66%, respectively, while the KJIc remains almost constant at 237 MPa m1/2. Dislocation-mediated plasticity prevails at 298 K; however, the TRIP from FCC to BCC occurs at 77 K. Deformation and fracture mechanisms are analyzed by stacking fault energies and differences in Gibbs free energies between phases calculated by ab-initio methods, and are compared to those of CrMnFeCoNi, CrCoNi, Fe50Mn30Co10Cr10, and V10Cr10Fe45Co20Ni15 alloys. Despite the presence of a considerable amount of BCC which is intrinsically brittle at low temperature, the transformed BCC martensite shows ductile fracture after the fracture toughness test even in cryogenic environments. These results demonstrate that the FCC to BCC TRIP can be an attractive route in a field of HEA design to overcome the strength and toughness trade-off at cryogenic temperature.

Highly sensitive, transparent, and durable pressure sensors are fabricated using sea-urchin-shaped metal nanoparticles and insulating polyurethane elastomer. The pressure sensors exhibit outstanding sensitivity (2.46 kPa-1 ), superior optical transmittance (84.8% at 550 nm), fast response/relaxation time (30 ms), and excellent operational durability. In addition, the pressure sensors successfully detect minute movements of human muscles.

Conductivity, calorimetry, and in-situ XRD can be closely interrelated with each other in terms of the sodium ion ordering and rearrangements in NASICON structure. An intermediate phase transition at 103 °C, not associated with heat effects, is evidenced for the first time, in addition to α–β and β–γ phase transitions at 64 °C and 166 °C. AC characterization of polycrystalline Na3Sc2(PO4)3 has been performed over the wide temperature range from 225 to − 100 °C. Strongly dispersive spectra of the low temperature monoclinic phase were systematically described by the total sample resistance connected by the several capacitive responses all in parallel: pure dielectric geometric capacitance and two Havriliak–Negami (HN) dielectric functions with opposite skewnesses. The capacitance strengths of HN functions are inversely proportional to the temperature and the relaxation times represent the thermally activated mobile charge carrier transport. While the higher frequency response with a negative skewness as γ = 0.388 and β = 1 is of a universal character common with many other solid electrolytes, known as K1 model, the lower frequency response with a positive skewness as γ ⋅ β ≈ 1 where β ≈ 0.59 and γ ≈ 1.67 describes the current-constriction effects occurring in the polycrystalline Na3Sc2(PO4)3. The current-constriction effects are described by a homogeneous polarization throughout the sample with 4 times the hopping distance and 5 times the relaxation time of the K1 response. 14 model parameters competently simulate the AC behavior over a wide temperature and frequency range.

The energetics of defects in the presence of domain walls in LiNbO₃ are characterized using density-functional theory calculations. Domain walls show stronger interactions with antisite defects than with interstitial defects or vacancies. As a result, antisite defects act as a strong pinning center for the domain wall in LiNbO₃. Analysis of migration behavior of the antisite defects across the domain wall shows that the migration barrier of the antisite defects is significantly high, such that the migration of antisite defects across the domain wall is energetically not preferable. However, further study on excess electrons shows that the migration barrier of antisite defects can be lowered by changing the charge states of the antisite defects. So, excess electrons can enhance the migration of antisite defects and thus facilitate domain wall movement by weakening the pinning effect.

A regioregular D1-A-D2-A terpolymer PDTSTTBDT incorporating dithieno[3,2-b:2′,3′-d]silole (DTS, D1) and benzo[1,2-b:4,5-b]dithiophene (BDT, D2) units with perfectly controlled thieno[3,4-b]thiophene (TT, A) orientation was synthesized for the first time. The thermal, optical, and electrochemical properties of the regioregular PDTSTTBDT were characterized and compared with the random PDTSTTBDT without structural regioregularity. The regioregular PDTSTTBDT showed ideal optical bandgap (1.45 eV), lower lying HOMO energy level, and higher degree of crystallinity compared to the random PDTSTTBDT. Moreover, it exhibited excellent solubility in nonhalogenated solvents as well as halogenated solvents. The inverted bulk-heterojunction polymer solar cells (PSCs) based on the regioregular PDTSTTBDT and o-xylene process solvent showed a power conversion efficiency as high as 6.14%, which is 500% higher than the random PDTSTTBDT-based PSCs. It was found that the remarkable enhancement of photovoltaic performance in re...

The development of an autonomous jellyfish removal robot system, named JEROS, and related experimental results are presented in this paper. The number of jellyfish has drastically increased due to changes to the marine environment. Large jellyfish swarms are threatening marine ecosystems and inducing enormous damage globally to marine-related industries. JEROS has been designed based on a twin hull-type surface vehicle equipped with a device for shredding jellyfish. Additionally, an electrical control system, a guidance, navigation, and control (GNC) system, and a vision-based jellyfish detection system are embedded to remove jellyfish autonomously. The jellyfish removal mission starts when the location of jellyfish is detected, followed by planning a path for jellyfish removal, tracking the path using an autonomous navigation system, and shredding jellyfish while tracking. The performance of the vision-based jellyfish detection, navigation, and jellyfish removal was demonstrated through experiments in a pond and field tests in Masan Bay located on the southern coast of South Korea.

Paperfolding sequences are represented by 0’s and 1’s. In this paper, we introduce paper-oor sequences which are represented by nonnegative integers. We investigate the structure of paper-oor sequences which represent the oors obtained by paperfoldings. Mathematics Subject Classication: 97A20, 68R99

A series of donor-acceptor (D–A) polymers with regioregularly incorporated a thieno[3,4-b]thiophene as a π-bridge between electron donor and electron acceptor segments were successfully synthesized for the first time. The optical, thermal, and electrochemical properties of the D–A polymers with the thieno[3,4-b]thiophene as a π-bridge were characterized by UV/vis spectroscopy, thermogravimetric analysis, and cyclic voltammetry measurements. They exhibited low energy bandgap because of extended π-conjugation length and increased electron density through conjugated polymer backbones. Moreover, they showed suitable HOMO and LUMO energy levels for photovoltaic applications. The bulk heterojunction organic photovoltaic devices based on the D–A polymers with the regioregularly incorporated thieno[3,4-b]thiophene segment exhibited about 10% higher power conversion efficiency (PCE) than the D–A polymer with thienyl segment as a π-bridge due to enhanced light harvesting ability and excellent nanoscale network. This study implies that the D–A polymers with the regioregularly incorporated thieno[3,4-b]thiophene segment as a π-bridge can achieve high PCE through structural modification of the polymers.

Reference-Frame-Independent Quantum Key Distribution (RFI-QKD) provides a practical way to generate secret keys between two remote parties without sharing common reference frames. On the other hand, Measurement-Device-Independent QKD (MDI-QKD) offers high level of security as it immunes against all the quantum hacking attempts to the measurement devices. The combination of these two QKD protocols, i.e., RFI-MDI-QKD, is one of the most fascinating QKD protocols since it holds both advantages of practicality and security. For further practicality of RFI-MDI-QKD, it is beneficial to reduce the implementation complexity. Here, we have shown that RFI-MDI-QKD can be implemented using fewer quantum states than those of its original proposal. We found that, in principle, the number of quantum states for one of the parties can be reduced from six to three without compromising security. Comparing to the conventional RFI-MDI-QKD where both parties should transmit six quantum states, it significantly simplifies the implementation of the QKD protocol. We also verify the feasibility of the scheme with the proof-of-principle experiment., A few revision has been made during the publication process

An ultra-sensitive and transparent piezoresistive pressure sensor based on a sea-urchin shaped metal nanoparticle (SSNP)-polyurethane (PU) composite with microdome arrays is successfully fabricated for the first time. The piezoresistive pressure sensor with microdome arrays was prepared using a nanoimprinting process based on an intermediate polymer substrate (IPS) replica mold. It showed a superior sensitivity (71.37 kPa-1) and a high optical transmittance (77.7% at 550 nm) due to the effective quantum tunneling effect even at small concentrations of conductive SSNP filler (6 mg mL-1). The high-performance characteristics of the piezoresistive pressure sensor are attributed to the geometric effects of the microdome structure, especially the stress concentration at small contact spots and the deformation of the contact area. The piezoresistive pressure sensor with microdome arrays also exhibited a fast response/relaxation time (30 ms), ultra-low pressure detection (4 Pa), and excellent long-term stability under harsh conditions. In addition, the effectiveness of the piezoresistive pressure sensors in various sensing applications including sensing mapping, human arterial pulse monitoring, and the detection of muscle movement is also successfully demonstrated. It is anticipated that this novel transparent pressure sensor based on a SSNP-PU composite with microdome arrays will be a key component in the development of integrated transparent sensing applications.

This paper proposes a surface crack detection method in concrete structures using image processing. Although many alternative methods using image processing have been suggested, non-crack parts are frequently detected as cracks, which make it difficult to obtain sufficiently accurate results. The proposed crack detection algorithm uses additional noise filtering steps after using the noise filtering proposed by the existing study. Finally, experimental results of the algorithm proposed by this study show cracks more clearly and indicate more effective noise removal.

This study explored perceptions of the integrated casino resort development in Korea and factors associated with a business license decision from the perspectives of the government representatives and industry professionals. Using a series of in-depth interviews with six selected Korean government representatives involved in the integrated casino project and with industry professionals, the study identified three categories and six main themes. The findings suggested that the participants perceived the integrated casino development as a great venture that will benefit the local community and the nation’s tourism industry. The findings also indicated that in addition to satisfying all of the bidding requirements, foreign investors’ financial integrity and health, as well as their business ethics standards, were considered the most important when the Korean government decided on a business license for the integrated casino resort. The study also found that while the Korean government recently changed a casino related law to provide better business opportunities for foreign investors, negative public perception toward the casino industry remains as a challenge

Ultra-long, uniform micro-fiber tapering technique is reported. Fabrication of a stand of 20-cm-long micro-fiber with the diameter of 1 μm and its transmission property will be discussed. Experimental results confirm the validity of our approach.

Localization is an essential issue for robot navigation, allowing the robot to perform tasks autonomously. However, in environments with laser scan ambiguity, such as long corridors, the conventional SLAM (simultaneous localization and mapping) algorithms exploiting a laser scanner may not estimate the robot pose robustly. To resolve this problem, we propose a novel localization approach based on a hybrid method incorporating a 2D laser scanner and a monocular camera in the framework of a graph structure-based SLAM. 3D coordinates of image feature points are acquired through the hybrid method, with the assumption that the wall is normal to the ground and vertically flat. However, this assumption can be relieved, because the subsequent feature matching process rejects the outliers on an inclined or non-flat wall. Through graph optimization with constraints generated by the hybrid method, the final robot pose is estimated. To verify the effectiveness of the proposed method, real experiments were conducted in an indoor environment with a long corridor. The experimental results were compared with those of the conventional GMappingapproach. The results demonstrate that it is possible to localize the robot in environments with laser scan ambiguity in real time, and the performance of the proposed method is superior to that of the conventional approach.

A sandwich-structured graphene/AgNW/graphene transparent conductive film (TCF) was prepared by embedding silver nanowires (AgNW) network with chemical vapor deposition (CVD)-grown graphene layers. The graphene/AgNW/graphene TCF exhibited excellent optical and electrical properties (88.6% at 550 nm and 19.9 ± 1.2 Ω/sq), which outperformed commercial indium tin oxide (ITO) film. Moreover, the graphene/AgNW/graphene TCF fabricated on a plastic substrate showed superior mechanical flexibility. In addition to the state of art performance, the reliability and long-term stability of the graphene/AgNW/graphene TCF were greatly enhanced because of the superior gas-barrier property of the graphene as the encapsulation layer. We anticipate that the sandwich-structured graphene/AgNW/graphene TCF can be a promising material to play a great role in realization of emerging optoelectronic devices such as OLEDs, LCDs, TSPs, and OSCs.

Correction for ‘Wafer-scale reliable switching memory based on 2-dimensional layered organic–inorganic halide perovskite’ by Ja-Young Seo, et al., Nanoscale, 2017, DOI: 10.1039/c7nr05582j.

Hysteresis and stability issues in perovskite solar cell (PSCs) hinder their commercialization. Here, we report an effective and reproducible approach for enhancing the stability of and suppressing the hysteresis in PSCs by incorporating a small quantity of two-dimensional (2D) PEA2PbI4 [PEA = C6H5(CH2)2NH3] in three-dimensional (3D) MAPbI3 [MA = CH3NH3 ] [denoted as (PEA2PbI4)x(MAPbI3)], where the perovskite films were fabricated by the Lewis acid–base adduct method. A nanolaminate structure comprising layered MAPbI3 nanobricks was created in the presence of 2D PEA2PbI4. For x = 0.017, a power conversion efficiency (PCE) of as high as 19.8% was achieved, which was comparable to the 20.0% PCE of a MAPbI3-based cell. Density functional theory (DFT) calculations confirmed that iodide migration was suppressed in the presence of the 2D perovskite as a result of a higher activation energy, which was responsible for the significant reduction in hysteresis and the improved chemical stability against a Ag electro...

Mixed halide perovskite materials are actively researched for solar cells with high efficiency. Their hysteresis which originates from the movement of defects make perovskite a candidate for resistive switching memory devices. We demonstrate the resistive switching device based on mixed-halide organic-inorganic hybrid perovskite CH3NH3PbI3−xBrx (x = 0, 1, 2, 3). Solvent engineering is used to deposit the homogeneous CH3NH3PbI3−xBrx layer on the indium-tin oxide-coated glass substrates. The memory device based on CH3NH3PbI3−xBrx exhibits write endurance and long retention, which indicate reproducible and reliable memory properties. According to the increase in Br contents in CH3NH3PbI3−xBrx the set electric field required to make the device from low resistance state to high resistance state decreases. This result is in accord with the theoretical calculation of migration barriers, that is the barrier to ionic migration in perovskites is found to be lower for Br− (0.23 eV) than for I− (0.29–0.30 eV). The resistive switching may be the result of halide vacancy defects and formation of conductive filaments under electric field in the mixed perovskite layer. It is observed that enhancement in operating voltage can be achieved by controlling the halide contents in the film.

Low-power operation of semiconductor devices is crucial for energy conservation. In particular, energy-efficient devices are essential in portable electronic devices to allow for extended use with a limited power supply. However, unnecessary currents always exist in semiconductor devices, even when the device is in its off state. To solve this problem, it is necessary to use switch devices that can turn active devices on and off effectively. For this purpose, high on/off current selectivity with ultra-low off-current and high on-current is required. Here, we report a novel switch behavior with over 109 selectivity, a high on-current density of 1 MA cm-2, an ultra-low off-current density of 1 mA cm-2, excellent thermal stability up to 250 °C and abrupt turn-on with 5 mV per decade in solution-processed silver-doped zinc oxide thin films. The selection behavior is attributed to light doping of silver ions in zinc oxide films during electrochemical deposition to generate atomic-scale narrow conduction paths, which can be formed and ruptured at low voltages. Device simulation showed that the new selector devices may be used in ultra-high-density memory devices to provide excellent operation margins and extremely low power consumption. A resistive switch device with a billion-fold difference between its conductive ‘on’ and insulating ‘off’ states has been developed. Next-generation memory cells that use differences in on/off current ratios to store information have low power requirements and can be stacked into three-dimensional arrays. But these devices can suffer from current leaking from nominally off cells. Now, Jang-Sik Lee from the Pohang University of Science and Technology in Korea and co-workers have used silver-doped zinc oxide thin films to diminish this effect. Fabricated by solution-processing precursors into nanoscale holes on a silicon wafer, these cells contain a dilute fraction of silver ions that form conductive filaments in the on state. The silver threads, however, break up into atomic constituents when the off state is accessed – a change that drops leakage current to insignificant, femtoamp levels. The novel switching behavior is observed in solution-processed silver-doped zinc oxide thin films. This switch exhibited high on-current density of 1 MA cm-2, ultra-low off-current of 100 fA, excellent thermal stability up to 250 °C, abrupt turn-on with 5 mV per decade and a high on/off ratio of 109. This study demonstrates that the switch devices can be applicable for selectors in ultra-high-density cross-point memory devices with excellent operation margin and extremely low power consumption.

Autonomous underwater vehicles (AUVs) are usually equipped with one or more optical cameras to obtain visual data of underwater environments. The camera can also be used to estimate the AUV's pose information, along with various navigation sensors such as inertial measurement unit (IMU), Doppler velocity log (DVL), depth sensor, and so on. In this paper, we propose a vision-based simultaneous localization and mapping (SLAM) of AUVs, where underwater artificial landmarks are used to help visual sensing of forward and downward looking cameras. Three types of landmarks are introduced and their detection algorithms are organized in a framework of conventional extended Kalman filter (EKF) SLAM to estimate both robot and landmark states. The proposed method is validated by an experiment performed in a engineering basin. Since DVL suffers from noises in a real ocean environment, we generated synthetic noisy data based on the real sensor data. With this data we verify that the proposed SLAM approach can recover from the erroneous dead reckoning position.

By combining ab initio molecular dynamics simulations and many-body perturbation theory calculations of electronic energy levels, we determined the band edge positions of functionalized Si(111) surfaces in the presence of liquid water, with respect to vacuum and to water redox potentials. We considered surface terminations commonly used for Si photoelectrodes in water splitting experiments. We found that, when exposed to water, the semiconductor band edges were shifted by approximately 0.5 eV in the case of hydrophobic surfaces, irrespective of the termination. The effect of the liquid on band edge positions of hydrophilic surfaces was much more significant and determined by a complex combination of structural and electronic effects. These include structural rearrangements of the semiconductor surfaces in the presence of water, changes in the orientation of interfacial water molecules with respect to the bulk liquid, and charge transfer at the interfaces, between the solid and the liquid. Our results showed that the use of many-body perturbation theory is key to obtain results in agreement with experiments; they also showed that the use of simple computational schemes that neglect the detailed microscopic structure of the solid-liquid interface may lead to substantial errors in predicting the alignment between the solid band edges and water redox potentials.

A visually servoed paired structured light system (ViSP) was recently proposed as a novel estimation method of the 6-DOF (Degree-Of-Freedom) relative displacement in civil structures. In order to apply the ViSP to massive structures, multiple ViSP modules should be installed in a cascaded manner. In this configuration, the estimation errors are propagated through the ViSP modules. In order to resolve this problem, a displacement estimation error back-propagation (DEEP) method was proposed. However, the DEEP method has some disadvantages: the displacement range of each ViSP module must be constrained and displacement errors are corrected sequentially, and thus the entire estimation errors are not considered concurrently. To address this problem, a pose-graph optimized displacement estimation (PODE) method is proposed in this paper. The PODE method is based on a graph-based optimization technique that considers entire errors at the same time. Moreover, this method does not require any constraints on the movement of the ViSP modules. Simulations and experiments are conducted to validate the performance of the proposed method. The results show that the PODE method reduces the propagation errors in comparison with a previous work.

We successfully fabricated silver nanowire (AgNW)-based microelectrodes on various substrates such as a glass and polydimethylsiloxane by using a photolithographic process for the first time. The AgNW-based microelectrodes exhibited excellent electrical conductivity and mechanical flexibility. We also demonstrated the direct transfer process of AgNW-based microelectrodes from a glass to a biocompatible polyacrylamide-based hydrogel. The AgNW-based microelectrodes on the biocompatible hydrogel showed excellent electrical performance. Furthermore, they showed great mechanical flexibility as well as superior stability under wet conditions. We anticipate that the AgNW-based microelectrodes on biocompatible hydrogel substrates can be a promising platform for realization of practical bioelectronics devices.

A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu(2) in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on Delta H-storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1',3,3'-tetra-tert-butyl (4), 1,2,2',3'-tetraphenyl (9), diiron (28), diosmium (24), mixed iron-ruthenium (27), dimolybdenum (29), and di-tungsten (30) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO3-SiO2 as a good candidate, although catalyst decomposition remains a challenge.

This paper deals with vision-based localization techniques in structured underwater environments. For underwater robots, accurate localization is necessary to perform complex missions successfully, but few sensors are available for accurate localization in the underwater environment. Among the available sensors, cameras are very useful for performing short-range tasks despite harsh underwater conditions including low visibility, noise, and large areas of featureless scene. To mitigate these problems, we design artificial landmarks to be utilized with a camera for localization, and propose a novel vision-based object detection technique and apply it to the Monte Carlo localization (MCL) algorithm, a map-based localization technique. In the image processing step, a novel correlation coefficient using a weighted sum, multiple-template-based object selection, and color-based image segmentation methods are proposed to improve the conventional approach. In the localization step, to apply the landmark detection results to MCL, dead-reckoning information and landmark detection results are used for prediction and update phases, respectively. The performance of the proposed technique is evaluated by experiments with an underwater robot platform and the results are discussed.

First-principles molecular dynamics simulations are used to gain an atomistic-level insight into how the molecular behavior of interfacial water is influenced by specific surface adsorbates. Although the overall hydrophobic versus hydrophilic character of a given surface is widely recognized to be important in determining the behavior of interfacial water molecules, we show that subtle molecular details may also play a role in determining the dynamical behavior of water. By comparing water diffusivity at three different nonpolar surfaces, we find that specific surface features can lead to a suppression of hydrogen bond network ring structures by enhancing hexagonal spatial distributions of water molecules near the surface. Such a distinct molecule-dependent behavior of the interfacial water was found to persist well into the liquid, while most structural properties are noticeably influenced in only the first water layer.

Representative face-centered-cubic (FCC) high-entropy alloys (HEAs) or medium-entropy alloys (MEAs), e.g., equi-atomic CoCrFeMnNi or CrCoNi alloys, have drawn many attentions due to the excellent damage-tolerance at cryogenic temperature. The investigation of fracture toughness at 77 K is basically required for the reliable evaluation of high-performance alloys used for cryogenic applications; however, it has been rarely carried out for the non-equi-atomic FCC HEAs yet. In this study, tensile and fracture toughness tests were conducted on the non-equi-atomic V10Cr10Fe45Co20Ni15 alloy, and the results were compared with those of the equi-atomic CoCrFeMnNi and CrCoNi alloys. The present alloy shows a good damage tolerance at cryogenic temperature with tensile strength of 1 GPa and elongation of ∼60%. The KJIc fracture toughness values are 219 and 232 MPa m1/2 at 298 and 77 K, respectively, showing the increase in toughness with decreasing temperature. This increase results from the absence of twins at 298 K and the increased propensity to twin formation at 77 K, which is well confirmed by the variation of stacking fault energies (SFEs) by using Ab-initio calculations. The mechanical properties of the present alloy are actually similar or slightly lower than those of the other CoNiCr or FeMnCoNiCr alloy; instead, this study provides that neither composition nor certain elements are the most important factors dictating damage-tolerance of HEAs or MEAs.

All-inorganic cesium lead triiodide (CsPbI3 ) perovskite is considered a promising solution-processable semiconductor for highly stable optoelectronic and photovoltaic applications. However, despite its excellent optoelectronic properties, the phase instability of CsPbI3 poses a critical hurdle for practical application. In this study, a novel stain-mediated phase stabilization strategy is demonstrated to significantly enhance the phase stability of cubic α-phase CsPbI3 . Careful control of the degree of spatial confinement induced by anodized aluminum oxide (AAO) templates with varying pore sizes leads to effective manipulation of the phase stability of α-CsPbI3 . The Williamson-Hall method in conjunction with density functional theory calculations clearly confirms that the strain imposed on the perovskite lattice when confined in vertically aligned nanopores can alter the formation energy of the system, stabilizing α-CsPbI3 at room temperature. Finally, the CsPbI3 grown inside nanoporous AAO templates exhibits exceptional phase stability over three months under ambient conditions, in which the resulting light-emitting diode reveals a natural red color emission with very narrow bandwidth (full width at half maximum of 33 nm) at 702 nm. The universally applicable template-based stabilization strategy can give in-depth insights on the strain-mediated phase transition mechanism in all-inorganic perovskites.

The adsorption of O2 on the TiN(001) stepped surface and the consequent formation of surface oxide have been characterized using first-principles calculations. The adsorption and dissociation of O2 on both the flat and the stepped surface are predicted to be spontaneous. Compared with the flat surface, however, the dissociation of O2 on the stepped surface is predicted to be more exothermic. A formation mechanism for TiO2 at the step is proposed that includes a nitrogen exit channel that enables further oxidation.