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Despite the fact that research into most high-performance thermoelectric (TE) materials is focused on tellurides, compelling demand has arisen to replace tellurium (Te) with selenium (Se) due to the scarcity of Te. Silver bismuth diselenide (AgBiSe2, ABS) has been widely studied in relation to thermoelectric applications due to its intrinsically low thermal conductivity. However, its low power factor (PF) has been considered as an underlying issue preventing improvements of the TE properties of ABS. Here, it is demonstrated that a high PF can be achieved by incorporating Cu into the ABS system via the nestification of conduction bands when a disordering between Ag and Bi occurs. Degenerate electronic bands simultaneously increase the density-of-states effective mass and carrier concentration while not reducing the carrier mobility significantly. Therefore, improved TE performance with a maximum PF of 8.2 μW cm−1 K−2 and a peak zT value of 1.14 was achieved at 773 K, opening a new horizon for the development of environmentally benign TE materials with high performance capabilities.

Charge carrier transport and corresponding thermoelectric properties are often affected by several parameters, necessitating a thorough comparative study for a profound understanding of the detailed conduction mechanism. Here, as a model system, we compare the electronic transport properties of two layered semiconductors, Sb

The selective reduction of thermal conductivity while preserving the Seebeck coefficient and electrical conductivity is regarded as a key strategy for achieving the high dimensionless figure-of-merit (ZT) of thermoelectric materials. Here, we newly propose a periodic three-dimensional (3D) nanostructure that has an ability to significantly reduce thermal conductivity, resulting in an improved ZT value of thermoelectric materials near room temperature. A 3D nanostructured thermoelectric monolith is developed by electrochemical deposition of a Bi–Sb–Te ternary alloy into a highly ordered, interstitial porous network in an epoxy template predefined by advanced lithography. The resultant inch-scale, bicontinuous nanocomposite monolith released from a substrate can be easily transferred to a customized reliable platform for evaluating thermoelectric properties. The measured thermal conductivity is only ∼0.89 W mK−1 at 350 K due to greatly increased phonon boundary scattering without any degradation in the Seebeck coefficient and electrical conductivity, leading to an enhanced ZT value (∼0.56) which is ∼50% higher than that of an ordinary film with the same elemental composition. The 3D nanostructure developed here will provide new design opportunities for nanostructured thermoelectric materials, potentially usable in flexible thermoelectric coolers and wearable energy harvesting systems.

Silver chalcogenides have received much attention in potential thermoelectric materials research because of high carrier mobility and low effective mass. Among them, in Ag2Te, it was reported that the phase transition from monoclinic to cubic phase occurs at relatively low temperatures, so that extensive research for effective application using this material has been aroused. In this work, we investigated how 1-dimensional nanostructure affects the thermoelectric properties through as-synthesized single crystalline Ag2Te nanowires. Adopting well-defined thermoelectric MEMS device structure and transferring an individual Ag2Te nanowire, we measure electrical resistance and Seebeck coefficient as a function of temperature. When the phase changes from monoclinic to cubic, the resistance increases, while absolute Seebeck coefficient value decreases. These results are compared with previous reports for Ag2Te bulk and film, suggesting the increased density of states of the carriers due to nanowire structure.

We investigate the quantum transport properties of surface electrons on a topological insulator Bi2Te3 nanowire in a magnetotransport study. Although the nanowires are synthesized by using a relatively coarse method of electrochemical deposition, clear Aharonov–Bohm oscillations of phases 0 and π are observed, owing to the highly coherent surface electron channel. The oscillation amplitude exhibits exponential temperature dependence, suggesting that the phase coherence length Lφ is inversely proportional to the temperature, as in quasi-ballistic systems. In addition, a weak antilocalization analysis on the surface channel by using a one-dimensional localization theory, enabled by successful extraction of the surface contribution from the magnetoconductance data, is provided in support of the temperature dependence of Lφ.

We present a MEMS-based device on a silicon nitride membrane in order to measure the thermoelectric properties of a single nanowire. A temperature gradient along a nanowire was generated by a nanoheater, and the temperature was measured by Pt thermometers. A thermal simulation using a finite element method was conducted to analyze the temperature distribution over the MEMS device. The validity of the MEMS device was established by testing the Pt nanowires which had different symmetry configurations. From the test results of Pt nanowires, a convincing temperature calibration method was proposed and applied to an actual case of Bi 2 Te 3 nanowire. We measured a Seebeck coefficient of −53 μV/K and electrical conductivity of 2.23 × 10 5 S/m for a single Bi 2 Te 3 nanowire with a diameter of 70 nm at 300 K. Our solid design for thermoelectric measurements based on a membrane structure enables the fast and high-yield characterization of one-dimensional nanostructures.

We suggest a facile and low-cost electrochemical growth mechanism that is generally applicable to the vertical growth of various one-dimensional (1-D) metal nanocrystals (Cu, AgCu and Au) without any templates or surfactants. At the initial deposition stage, hemispherical islands are uniformly formed on a substrate by repetition of nucleation and dissolution processes under a reverse-pulse potentiodynamic mode. 1-D growth then occurs due to a dissolution process as well as a filamentary effect, i.e., strong interface anisotropy enhanced by field enhancement at the top of the hemispherical islands in an ultra-dilute electrolyte having a low electrical conductivity of less than 100 μS cm −1 . The diameters of 1-D nanocrystals are controllable by the reduction potential and the electrical conductivity of the electrolyte. The 1-D Cu, AgCu, and Au nanocrystals have a multiply twinned crystal structure and grow in the 〈1 1 1〉-longitudinal direction.

We systematically investigated the role of topological surface states on thermoelectric transport by varying the surface-to-volume ratio (s/v) of Bi2Se3 nanowires. The thermoelectric coefficients of Bi2Se3 nanowires were significantly influenced by the topological surface states with increasing the s/v. The Seebeck coefficient of Bi2Se3 nanowires decreased with increasing the s/v, while the electrical conductivity increased with increasing the s/v. This implies that the influence of metallic surface states become dominant in thermoelectric transport in thin nanowires, and the s/v is a key parameter which determines the total thermoelectric properties. Our measurements were corroborated by using a two-channel Boltzmann transport model.

Amorphous SnO nanotubes were synthesized from Sn nanowires (NWs) electrodeposited into anodic aluminum oxide templates by a localized corrosion process in an aqueous solution composed of chromic, phosphoric, and hydrochloric acids. Initially, phosphoric acid dissolves the template, while chromic acid generates a SnO passivation layer on the NW surface. As a volume expansion occurs during the surface oxidation, some cracks occur at the top surface of the passivation layer. In addition, Cl ions from the hydrochloric acid assist the cracking. Subsequently, Sn atoms in the core of the NW dissolve into the acidic solution while the oxide layer at the shell remains to form nanotubes. Finally, Sn NWs with a length of 10 μm and diameter of 30 nm are completely transformed to amorphous SnO nanotubes with a wall thickness of 10 nm. After heat-treatment, the amorphous nanotubes were crystallized into polycrystalline SnO phase with a rough surface morphology.

A simple, cost-effective, and highly reliable method for constructing an air-bridged electrical contact on large arrays of vertically aligned nanowires was developed. The present method may open up new opportunities for developing advanced nanowire-based devices for energy harvest and storage, power generation, and sensing applications.

This paper studies design of a virtual robotic arm based on electromyography (EMG), gyroscope and accelerometer. Data from a Myo armband which detects various living body signals is delivered through Bluetooth to a virtual robotic arm which is built in Unity 3D. EMG is electrical signal generated by tension and relaxation of muscles and a virtual robotic arm based on EMG is available to control minute movements of forearm muscles without dynamic motions. Thus, a virtual robotic arm based on EMG is more suitable to develop applications for hand amputee than a virtual robotic arm based on gyroscope and accelerometer.

The size dependence of the lattice parameter of nanosolids has extensively been studied because lattice strain engineering is important in controlling the physical properties of nanowires (NWs), such as band gap, carrier transport, mechanical strength, etc. We have investigated the size-dependent lattice behavior of microstructure-controlled Sn NWs with radii of 7–35 nm. The NW microstructures were controlled as single-crystal, granular, and bamboo structures in the longitudinal direction. Results showed that the a-axis lattice parameter in the [100]-longitudinal direction of NWs can be controlled within 1% by varying the wire microstructure for the same wire radius because it is strongly dependent on the microstructure and the wire radius. Moreover, as the randomness of the grain orientation in the microstructure-controlled NWs increases, by which the anisotropy of surface stress is effectively reduced, the lattice strain of the NW can be compressive or tensile as a function of the wire radius. The longitudinal lattice parameters of microstructure-controlled Sn NWs can be tailored by reducing the effective anisotropy of surface stresses under a dimension confinement in the nanometer scale.

Modern people can use navigation on the outside to save time and get to the destination well. Likewise, in order to find out more information about a destination building, such a system is increasingly needed both in front of the computer (on-line) of the house and after reaching the destination in the building (off-line). Accordingly, we employ Building Information System (BIS) as a system that provide users with content related to a building like BIO and BIM. The Building Information Online system (BIO) is an interactive map application designed to assist customers in finding parcels and building on a map online. The Building Information Modeling (BIM) allows nD information to be visualized simultaneously by architects, engineers and constructors to gain a synchronized understanding viewing from different perspectives. Inspired by above researches, we implement a service that provides online and offline Virtual Reality (VR) and Augmented Reality (AR) content for a building. This system can provide users outside the building with information within the building via devices with VR and AR support regardless of space restrictions. The system is designed to operate across scenarios requiring offline, online, offline-online collaboration, etc., and the corresponding experiments are carried out.

The fuzzy control and implementation of a new three-dimensional(3-D) inverted pendulum system are addressed. In comparison with conventional 1-D and 2-D systems, the 3-D inverted pendulum system is a proper benchmark system to simulate human`s control action which includes the up and down motion to stabilize an inverted pendulum. To investigate the characteristics of the 3-D inverted pendulum system and to design of a fuzzy controller, we derive dynamic equations of the mechanism including a 3-axis cartesian robot and an inverted pendulum. We propose a design method of a fuzzy controller of the yaw and pitch angles of an inverted pendulum. In the design, the redundant degree-of-freedom(DOF) of the robot and the constrained workspace are taken into account. The performance of the proposed system is proved by experimental results using a developed PC-based Multi-Motion Control(MMC) board.

Bi2Se3 nanoplate devices are synthesized on SiO2 and ferrimagnetic insulator substrates. We experimentally demonstrate that ferromagnetism is induced into the bottom surface. The symmetry broken bottom states give rise to an additional Shubnikov–de Haas frequency and leads to a decoupling of the top and bottom quantum Hall effects. We present a three-channel model that separates the bulk, top and bottom surface contributions to the Hall resistance, indicating the presence of two symmetry shifted half-integer QHEs.

Thermoelectric figure-of-merits (ZT) are enhanced or degraded by crystal defects such as twins and excess atoms that are correlated with thermal conductivity (k) and carrier concentration (n). For Bi2Te3, it is unclear whether the crystal defects can enhance ZT without a degradation in the thermopower factor. In the present study, n-type Bi2Te3 nanowires (NWs) are electrochemically synthesized to have twin-free (TF) or twin-containing (TC) microstructures with a ZT of 0.10 and 0.08, respectively, at 300 K. The ZTs of TF and TC NWs remarkably increase up to 0.21 and 0.31, when heat-treatments cause n-reduction and twins induce phonon scattering, as follows: first, the enhancement of the Seebeck coefficient from -70 to -98 μV K(-1) for TF NWs and from -57 to -143 μV K(-1) for TC NWs, by virtue of n-reduction; secondly, twin-driven k-reduction from 1.9 to 1.4 W m(-1) K(-1) of TC NWs, while the k of TF NWs increases from 2.3 to 2.6 W m(-1) K(-1) due to the enhanced carrier mobility. The lattice thermal conductivities of TC NW are lowered from 1.1 to 0.8 W m(-1) K(-1) by phonon scattering at twins. Density functional theory calculations indicate that twins do not significantly influence the Seebeck coefficient of Bi2Te3. It is strongly recommended that twins be incorporated with an optimum carrier concentration to enhance the ZT of Bi2Te3.

Nanowires of Cu 2 O as well as Cu were synthesized within the anodic aluminum oxide templates in an aqueous acidic electrochemical cell. The content of Cu 2 O in the copper nanowires was controlled by varying the anodic potential of the pulse-reverse electrolysis and the pH of the electrolyte within a range of 2.0–3.9. For the pH of 2.0, pure Cu nanowires were deposited regardless of the anodic potential. When the anodic potential became higher than the cathodic one, pure Cu 2 O nanowires were produced at a pH of 3.9. The growth of Cu 2 O nanowires in the acidic electrolyte was ascribed to the local increase of the pH at the pore base, as well as the capacitive barrier layer of the template.

The physical properties of materials on a nanometer scale are known to be different from those of bulk form due to dimensional confinement effects and high specific surface-to-volume ratio. In this study, the size effects on the diffusion and reaction at the interface of dissimilar nanowires (NWs) were investigated. Co/Sb-multilayered NWs of15±1and19±2 nm in radius have been grown within anodic aluminum oxide templates using a pulsed potentiodynamic electrodeposition method. XRD and TEM results demonstrated that the multilayered NWs were transformed to a CoSb phase through a solid-state reaction at the temperature in the range of 653 to 693 K. The kinetics of the solid-state reaction was analyzed and found to be diffusion controlled at the interface between Co and Sb phases. The reaction was controlled by the dominant diffusion of Sb atoms. The activation energies for the solid-state reaction were estimated to be 0.9 and 0.7 eV/atom for the multilayered NWs with radii of 15 and 19 nm, respectively.

Nano-interconnection technology is expected to replace some part of solder bump technology of electronic packaging in near future. Metallic nanowires (NWs) are one of the candidates for the electrical interconnection materials. In this study, as a well-known material for the interconnection in the electronic packaging, Sn was selected for the application to nano-interconnection technology. Since the physical properties of Sn NWs are important for the interconnection applications, we have already reported the size-dependency of melting behaviors and lattice parameters of single crystalline Sn NWs. In this study, the effects of the NW microstructure and the kinds of templates, which were used for the growth of Sn NWs, on the lattice parameter were investigated. Results showed that the single crystalline Sn NWs were elongated along the longitudinal direction up to 0.64 % depending upon their microstructures and kinds of the templates. The nanowire elongation was gradually reduced when the NW microstructure were single crystalline, granular, and bamboolike structures, in sequence.

Resistive switching characteristics of single-crystalline CuO nanowires grown by thermal oxidation was investigated. The compressive stress developed in Cu2O layer prevented further oxidation of Cu and caused CuO nanowire growth, which was driven by the total Gibbs free energy minimization. CuO nanowire with Pt electrode showed Ohmic below 1.1 V and space charge limited current above 1.1 V, while that with Cu electrode showed resistive switching characteristics with sufficient Cu ions to form the metallic filaments from the electrodes.

Silver nanowires (NWs) are currently fabricated via template-free or template-assisted methods. The former is based on a medium-mediated anisotropic synthesis, which enables precursor atoms to be selectively adsorbed onto specific crystallographic planes, and the latter is performed via directional growth guided by preformed templates. These methods are costly and complicated. We outline a facile and low-cost approach for the electrochemical synthesis of silver NWs in a manner that is template- and surfactant-free and that provides control over the NW diameter in the range of 80 to 800 nm by the repetition of nucleation and dissolution. The nanowires vertically grow with the help of the interface anisotropy driven by a field enhancement at the tips of the islands nucleated on the substrate in ultra-dilute electrolytes (ca. 10(-5) M), which is similar to a lightning-rod effect. The silver nanowires of vertical configuration are utilized for fabrication of anisotropic conducting, transparent, and flexible films.

Cu2O/Cu nanowires of about 2 µm length were electrodeposited within anodized aluminum oxide templates in an aqueous acidic solution using template-assisted pulse-reverse electrolysis. In the virgin state, reversible copper filaments were formed by using the copper ions driven by an electric field towards the cathode. Initially, the resistive switching dominated the electrical characteristics of the Cu2O/Cu nanowires due to the low-resistance reversible copper filaments. After the permanent breakup of the copper filaments under the high current density, the Cu2O/Cu nanowire showed bipolar exponential characteristics, which was attributed to mixed ionic and electronic conduction.

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We report on size-dependent lattice expansion of single crystalline Sn nanowires (NWs) with the wire radius (rNW=6.9–34.7 nm), where the NWs are deposited under confinement of a nanotemplate. The longitudinal lattice expansion in the NWs increases up to approximately 1.0% with the reciprocal radius (1/rNW), contrary to the general theoretical prediction that the surface relaxation causes lattice contraction of nanomaterials. The longitudinal dilatation of the NW lattice can be understood by the Poisson effect induced by the compressive growth stress in the radial direction, which increases with the reciprocal radius.

Thermal instability and melting behavior of tin nanowires were studied with a decrease of wire radius(rNW=7–30nm) via differential scanning calorimetry (DSC). Two sequential DSC measurements showed a 1∕rNW dependency of the melting temperature depression; the first melting temperature decreased from 502to486K with 1∕rNW whereas the second one was more depressed between 0.8 and 5K. The melting temperature difference between the first and second cycles increased linearly with 1∕rNW. This variation was attributed to fragmentation of nanowires due to Rayleigh instability. Here, fragmentation of long nanowires was suppressed by a template confinement, resulting in the formation of short nanorods.