bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wearable Photodiodes & Arduino Made on Fabrics for Smart Fashion
Authors: Lee Wonjae , Abdur Rahim , Singh Son , Kuddus Sheikh Md Abdul , Paik Kyung-wook , Lee Jaegab 
Published: December 2020

Advances in the development of the flexible sensors, low power radio communication systems, and miniature electronic components allow for the application of wearable devices and the smart fashion. Moreover, healthcare has become a general awareness. People are urging to detect health issues as the earliest stage as possible. The use of conventional technologies are expensive and hindered the performance & wearable due to mechanical rigid & non-flexibility. Therefore, low cost and excellent flexibility with high mechanically stable & wearable health trackers are needed to monitor health issues based on optical detection due to their noninvasive tracking of vital health issues. . Here, we demonstrate hybrid perovskite based flexible photodetector for wearable sensor devices and we have designed a photo sensor module on fabrics which is able to transfer signals wirelessly to cell phones & PC systems. It is useful for wearable health monitoring & smart fashion cloths.
In this study, we discuss the design and experimental demonstration of hybrid perovskite based photodetector which is integrated into flexible photo sensor module on fabric. We have fabricated perovskite-based flexible photodetector consisting of ITO/CdS/perovskite/s-V2O5/Au, focusing on the conformal coating of perovskite on the planar CdS by addition of PbBr2 and PbCl2 to PbI2, which significantly increases the nucleation rate of perovskite, the leading to highly smooth surface morphology of perovskite. This enhances the performance of photodetectors. The devices are fabricated on flexible substrate which withstand many bending cycles at a submillimeter radius without degradation of optoelectronic properties. This wearable smart photo sensor module is able to monitor vital health issues including heart rate & oxygen saturation level in blood. Our findings provide a hybrid perovskite photo sensor module for photonic devices to improve their role in the area of flexible & mechanically stable and wearable optoelectronic systems.
Novel Processing of Tin Monosulfide Single Crystals
Authors: Nose Yoshitaro , Takemura Tomoki , Katsube Ryoji 
Published: December 2020

Tin monosulfide (SnS) is an attractive semiconductor for electronic and optoelectronic applications such as thin-film photovoltaics, due to the optical and electrical properties, earth-abundance of the composing elements, and the layered crystal structure. One of issues under active discussion in SnS-based devices is how to prepare SnS without sulfur-rich secondary phases such as SnS2 and Sn2S3, which are easily formed in processes such as sulfurization of tin. In contrast, we have been established the processing to prepare single-phase SnS by distillation from Sn/SnS composites based on chemical thermodynamic calculations on the S-Sn binary system.
Sn/SnS composites were prepared by heat-treatment of tin shots and sulfur flakes in a evacuated quartz ampule. The composites were again sealed in an ampule, and the distillation was carried out using Bridgman furnace. SnS bulk single crystals were obtained by unidirectionally cooling from the opposite side of composites. The crystals can be easily cleaved along to the layer plane, and secondary phases were not confirmed. The electric properties in the plane of single crystals are a p-type conduction with high carrier mobility of 100 cm2V-1s-1, which is advantage for an application to solar cell devices.
Electric and Photoelectrochemical Properties of CuGaSe2 Single Crystal
Authors: Ikeda Shigeru , Fujita Wakaba , Nose Yoshitaro , Katsube Ryoji , Yoshino Kenji , Harada Takashi 
Published: December 2020

The CuGaSe2 compound is a promising material as a photoabsorber of solar cell due to its p-type semiconductive characteristic and optimum band gap for sunlight absorption (1.68 eV). This compound is also attractive for the use of a photocathode for photoelectrochemical (PEC) water splitting because of its sufficient negative energy level of conduction band minimum (CBM) to induce reduction of water. For such applications, a thin-film form of the compound is usually used. In order to clarify and control its bulk and/or surface properties optimal for photovoltaic and PEC applications, we attempted to use a single crystalline form of the compound obtained by using a conventional vertical Bridgman technique.
Several crystallographic and compositional analyses indicated successful formation of the CuGaSe2 single crystal. Electronic properties of the thus-obtained single crystal measured after processing into a wafer form suggested a p-type semiconductive characteristic responsible for the use of photocathode. However, due to the insufficient acceptor concentration, the PEC property of the sample was not enough as was expecting it to be. After various trial, post annealing in a Se vapor atmosphere was found to be effective for improvement of its PEC functions. Details on effects of the annealing on the photovoltaic and the PEC hydrogen evolution properties were examined.
Electric Field Thermopower Modulation Analyses of the Operation Mechanism of Transparent Amorphous SnO2 Thin-Film Transistor
Authors: Liang Doudou , Zhang Yu-qiao , Cho Hai Jun , Ohta Hiromichi 
Published: December 2020

Transparent amorphous oxide semiconductors (TAOSs) based transparent thin film transistors (TTFTs) with high field effect mobility (μ
FE) are necessary to develop advanced flat panel displays. Currently, amorphous (a-) InGaZnO4 is widely applied as the TAOS of the TFT channel of the commercially available OLED displays with a μ
FE is ~10 cm2 V−
1 s−
1[1]. Among TAOSs, amorphous (a-) SnO2 has several advantages against current a-InGaZnO4 such as higher μ
FE >100 cm2 V–1 s–1[2], which is one order of magnitude higher than that of a-InGaZnO4 and indium free. Although there are several researches on a-SnO2 TTFT, the operation mechanism has not been clarified thus far due to the strong gas sensing characteristics of SnO2.
We prepared a bottom-gate top-contact type TTFT by pulsed laser deposition technique using 4.2-nm-thick a-SnO2 as the channel without any surface passivation. We measured the transistor characteristics and thermopower(S) in air and vacuum. The resultant a-SnO2 TTFT showed clear transfer (I
d–V
g) characteristics (FIG. a) with the on-to-off current ratios of ~105. All the TTFTs show clear pinch-off in the output characteristics. The threshold voltage (V
th) was −14 V in air whereas it shifted dramatically to −23 V in vacuum shows a strong gas sensing characteristic. An almost linear relationship with a slope of ~120 μV K−1 decade−1 was observed in the –S–log n
s plot (FIG. b) when n
s exceeded 2.5 × 1012 cm−2 in air and a slope of ~84 μV K−1 decade−1 was observed in the –S–log n
s plot when n
s exceeded 2.9 × 1012 cm−2 in vacuum indicating that the E−k relation at the bottom of the conduction band is parabolic shaped. The t
eff ≡ n
s/n
3D of the conducting a-SnO2 channel were always ~1.7 ± 0.4 nm, insensitive to the gas atmosphere (FIG. c). From the thickness of the a-SnO2 film (4.2 nm) and the t
eff (1.7 ± 0.4 nm), the carrier depletion depth at the top surface was concluded to be 2.5 nm of the a-SnO2 film, which shows the similar depletion length as reported data.[4] The present results would provide a fundamental design concept to develop a-SnO2 TTFT.
[1] K. Nomura et al., Nature, 432, 488 (2004).
[2] C. W. Shin et al., Sci. Rep.
6, 19023 (2016).
[3] N. Yamazoe, Sensor Actuat. B-Chem.
5, 7 (1991).
[4] D. Liang et al., Appl. Phys. Lett.
116, 143503 (2020)

Figure 1
Suppression of Anisotropic Heat Conduction in Ion-Substituted Layered Cobalt Oxides
Authors: Ohta Hiromichi , Cho Hai Jun , Takashima Yugo , Onozato Takaki 
Published: December 2020

Layered compounds often show the anisotropic transport properties of both electron and phonon; the electrical/thermal conductivity along with the layer is high and the electrical/thermal conductivity perpendicular to the layer is low. For example, layered Na
x
CoO2, which is known as a promising candidate for oxide thermoelectric material [1], exhibits a rather large thermoelectric power factor along with the CoO2 layer, whereas it shows low electrical conductivity in perpendicular to the CoO2 layer. In addition, the thermal conductivity is large along with the CoO2 layer, whereas it is small in perpendicular to the CoO2 layer. Therefore, the anisotropic electron/phonon transport properties need to be suppressed to improve the thermoelectric figure of merit of Na
x
CoO2. Here we demonstrate that the anisotropy in thermal conductivity κ of Ax
CoO2 (A = Li, Na, Ca, and Sr) can be suppressed by increasing the weight of Ax
. We fabricated Ax
CoO2 epitaxial films with two different crystallographic orientations with respect to the surface normal to the substrates by the Reactive Solid-Phase Epitaxy method [2,3]. We measured the electrical conductivity σ and thermopower S along with the substrate surface whereas we measured the κ in normal to the substrate surface. We extracted the κ parallel to the layers (κ
p) from the comparison of two different crystallographic orientations [4]. The κ
p was 3-6 times larger than that perpendicular to the layers (κ
v). The κ
p decreased with increasing the atomic mass of Ax
though κ
v was insensitive to it; anisotropy of κ was controlled by substituting heavier Ax
-ions [5]. The results of this study will be of great value in understanding fundamental heat transport properties of layered structures as well as developing Ax
CoO2 based thermoelectric materials. In addition, the analysis of the anisotropic thermal conductivity used in this study can be applied to other layered materials.
[1] I. Terasaki et al., Phys. Rev. B
56, R12685(R) (1997).
[2] H. Ohta et al., Cryst. Growth Des.
5, 25 (2005).
[3] K. Sugiura, H. Ohta et al., Appl. Phys. Lett.
88, 082109 (2006).
[4] K. Sugiura, H. Ohta et al., Appl. Phys. Lett.
94, 152105 (2009).
[5] H.J. Cho, H. Ohta et al., Adv. Mater. Interfaces
7, 1901816 (2019).

Figure 1
Non-Stoichiometric Ferroelectric Bismuth Ferrites (Bi25FeO40) Enhancing Photocatalyst Activity in the Acidic Environment
Authors: Wu Guan Hua , Wu Jyh-Ming 
Published: December 2020

In this work, non-stoichiometric bismuth ferrites (Bi25FeO40) particles that possess ferroelectric and photocatalysis properties were synthesized by the hydrothermal method. According to our previous work, piezoelectric materials can be employed in numerous applications. When applied to organic dye degradation, the photocatalysis effect is largely enhanced with the assistance of ferroelectricity[1, 2]. The Bi25FeO40 belongs to the I23 space group, which is a non-centrosymmetric piezoelectric crystal structure. The piezoelectricity is investigated by utilizing the piezoresponse force microscope (PFM) to measure its bias to phase relation. The lifetime of electron-hole pairs stimulated by laser could be measured by photoluminescence (PL) and time-resolved photoluminescence (TRPL). Due to its ferroelectricity, when the poling electric field raised, the remnant polarization and lifetime were increased; the intensity of the PL spectrum dropped reversely[2, 3]. This represents the recombination possibility of the electron-hole pairs were decreased by the poling process. Moreover, by adjusting the pH value of the degradation environment, the contact ability of the dye molecules and catalysts was improved. Under the condition of pH=3.5, the Rhodamine B (RhB) dye can be fully degraded in one hour while there is only 16% degraded in one hour of the original RhB solution(pH=4.8). This work demonstrated a photocatalyst assisted by ferroelectric property which could be enhanced through the poling process and prolong the lifetime of the electron-hole pairs. Furthermore, it shows greater degradation ability on RhB dye in acidic environment due to the better contact ability with the dye molecules, which makes it a new choice of acidic industrial wastewater treatment.
References:

Wu, M.-H., et al., Ultrahigh efficient degradation activity of single- and few-layered MoSe2 nanoflowers in dark by piezo-catalyst effect. Nano Energy, 2017. 40: p. 369-375.

Wang, Y.-C. and J.M. Wu, Effect of Controlled Oxygen Vacancy on H2-Production through the Piezocatalysis and Piezophototronics of Ferroelectric R3C ZnSnO3 Nanowires. Advanced Functional Materials, 2020. 30(5): p. 1907619.

Liu, Y.L. and J.M. Wu, Synergistically catalytic activities of BiFeO3/TiO2 core-shell nanocomposites for degradation of organic dye molecule through piezophototronic effect. Nano Energy, 2019. 56: p. 74-81.
Multi-Functional Flexible Sensor Sheets for Iot Society
Authors: Takei Kuniharu 
Published: December 2020

Multiple sensing functionalities enable to collect a variety of information for the next class of Internet of Things (IoT) concept such as medical/healthcare, robotics, environment, and infrastructures. In addition to the functionalities, mechanical flexibility allows to attach the devices over non-planar surfaces conformally, resulting in that more information can be monitored precisely. In particular, multi-functional electronic skin (e-skin) can contribute to the applications of robotic skin and infrastructure due to low-cost, macro-scale devices that can cover a variety of objects. In this talk, soft robotics with e-skin functions and air flow mapping for the infrastructure applications are mainly discussed.
For the soft robots with e-skin, tactile pressure distribution and temperature of the holding object are simultaneously detected by integrating these sensors on the tip of soft robot finger. Next, for the infrastructure monitoring, flexible air flow sensor array is demonstrated to monitor air flow distribution on the curved surfaces. For the flow sensor, calorimetric methodology is used to monitor the temperature distribution generated by a printed flexible heater. This heat distributions are detected by printed temperature sensors. Integration of these heaters and temperature sensors, as the first proof-of-concept, realizes real-time air flow mapping on the curved surface successfully.
Automatic Deposition of Oriented Copper Hydroxide Nanobelt Films for the Heteroepitaxial Growth of Metal-Organic Frameworks
Authors: Linares-Moreau Mercedes , Klokic Sumea , Carraro Francesco , Falcaro Paolo 
Published: December 2020

One of the key challenges that the field of metal-organic frameworks (MOFs) faces today is the possibility of processing these materials as thin films to enable their integration into existing technologies [1-4]. This is particularly important for devices that exploit anisotropic properties obtained from highly oriented materials. Based on a previously described procedure to obtain centimetre-scale oriented MOF films [5], we hereby report the optimization and extension of this procedure into an automated, operator-independent method that affords higher yields without compromising the long-range orientation. The procedure is based on the deposition of crystalline copper hydroxide nanobelts that can be aligned to obtain substrates with preferential orientation. The influence of different deposition parameters on the coverage and orientation of the films was studied and tuned in order to obtain reproducible samples with higher yields. With applications in fields such as gas storage, catalysis and light harvesting, among others, these oriented ceramic substrates can be converted on demand to different MOFs by exploiting a rapid heteroepitaxial growth [6]. This automatic method introduces the attractive prospect of the potential implementation of MOFs in large-scale thin-film processing.

Figure 1:

Comparison between manual and automated procedures for the deposition of oriented copper hydroxide films on silicon substrates. Left: Azimuthal angle dependence of intensity profiles of the (020) reflection of Cu(OH)2 at a diffraction angle of 23.8°corresponding to a typical sample obtained by each method, showing the superior alignment of the automatic procedure. Right: Optical images showing the surface coverage and long range (centimetre-scale, top) and micro alignment of the substrate (by polarized-light optical microscopy, bottom).

References:

[1] Bétard, A.;Fischer, R.A. Chemical reviews
2011, 112, 1055
[2] Falcaro, P.; Ricco, R.; Doherty, C.M.; Liang, K.; Hill, A.J.; Styles, M.J. Chemical Society Reviews
2014, 43, 5513
[3] Stassen, I.; Burtch, N.; Talin, A.; Falcaro, P.; Allendorf, M.; Ameloot, R. Chemical Society Reviews
2017, 46, 3185
[4] Liu, J.; Wöll, C. Chemical Society Reviews
2017, 46, 5730
[5] Falcaro, P.; Okada, K.; Hara, T.; Ikigaki, K.; Tokudome, Y.; Thornton, A. W.; Hill, A. J.; Williams, T.; Doonan, C.; Takahashi, M.; Falcaro, P. Nature materials
2017, 16, 342.
[6] Ikigaki, K.; Okada, K.; Tokudome, Y.; Toyao, T.; Falcaro, P.; Doonan, C.J.;Takahashi, M. Angewandte Chemie 2019, 131, 6960.

Figure 1
(Invited) Three-Dimensional Nanostructuring of Metal-Organic Frameworks for Energy Applications
Authors: Tricoli Antonio 
Published: December 2020

Metal-organic frameworks (MOFs) are a growing family of microporous materials that are attracting significant research and industrial interest, thanks to their unique features including a tuneable and narrow intrinsic pore size distribution, and very high surface area. MOFs are also being increasingly used as a precursor for the preparation of well-dispersed metal-containing carbon electrodes. A major challenge remains the three-dimensional structuring of MOFs into hierarchical functional morphologies and their integration as active elements in electrical material systems, due to their usually low electronic conductivities. Here, we present some flexible strategies for the structuring of MOFs into three-dimensional morphologies and their application for energy storage. In particular, we focus on lithium–sulfur (Li–S) batteries as a promising system for the next-generation of high energy density batteries. Despite progress, the energy density of current Li–S technologies is still below that of conventional intercalation-type cathode materials, due to limited stability and utilization efficiency at high sulfur loading.
We demonstrate a highly performing free-standing monolithic electrode architecture for Li–S batteries with superior electrochemical stability and energy density [1]. The electrode layout consists of a highly conductive three-dimensional network of N,P co-doped carbon with well-dispersed metal-organic frameworks nano-domains of ZIF-67 and HKUST-1. The hierarchical monolithic 3D carbon networks provides an excellent environment for charge and electrolyte transport as well as mechanical and chemical stability. The electrically-integrated MOF nano-domains significantly enhance the sulfur loading and retention capabilities by inhibiting the release of lithium polysulfide specifies as well as improving the charge transfer efficiency at the electrolyte interface. Our optimal 3D carbon-HKUST-1 electrode architecture achieves a very high areal capacity of > 16 mAh cm−2 with a capacity retention of 82 % at 0.2C for over 300 cycles, providing an attractive candidate material for future high energy density Li–S batteries. We believe that our approaches provide some promising directions for the engineering of functional MOF morphologies for electrochemistry.

References

Liu, B.; Bo, R.; Taheri, M.; Di Bernardo, I.; Motta, N.; Chen, H.; Tsuzuki, T.; Yu, G.; Tricoli, A. Nano Lett.
2019, 19, (7), 4391-4399.
Gallium Telluride Based Phase Change Materials for Neuromorphic Photonic Applications
Authors: Bychkov Eugene 
Published: December 2020

Neuromorphic photonics intensively uses classical phase-change materials based on GeTe-Sb2Te3 (GST) composition line either to develop on-chip non-volatile photonic memories [1] or artificial synapses for complex integrated photonic systems capable of the image recognition [2]. The GST materials were originally designed for DVD and Blu-ray disks and not necessarily fully optimized for neuromorphic applications. As a possible alternative, we will present here structure and properties of gallium telluride based systems. The structural studies using hard x-rays and ab initio molecular dynamics modeling will be compared with corresponding results for GST phase-change alloys.
[1] C. Rios, M. Stegmaier, P. Hosseini, et al. Nature Photonics 9 (2015) 725.
[2] J. Feldmann, N. Youngblood, C. D. Wright, et al. Nature 569 (2019) 208.
Macroscopic Modeling of Liquid Water in Channel of Jari Cell Based on Detailed Two-Phase CFD
Authors: Tanaka Shoichi , Takayama Tsutomu , Tsukamoto Takayuki , Motegi Haruki , Takayama Ryo , Komiyama Keisuke , Yoneda Masakazu 
Published: December 2020

In this work, we modeled liquid water behavior in channels based on detailed two-phase CFD for application on Full-Cell scale multiphysics simulation. In our work, in order to execute efficient simulations in full-cell scale, all relevant transport phenomena in PEFC (mass, chemical species, and heat) are considered macroscopic, where the phenomena are coupled with electrochemical reactions. In order to apply this method for conditions in which liquid water is important, two-phase fluid models should be constructed properly.
In order to model two-phase flow in channels, we evaluated the relationship between liquid water volume fraction, pressure drop, and liquid water velocity in macroscopic control volume with detailed CFD using OpenFOAM. The calculation target is the JARI cell channel and mesh size is 50 micrometer order. We used the interIsoFoam for the solver, which uses the VOF method for two-phase flow and geometric surface reconstruction method for surface capturing. The relationship is expressed by the table data that shows the relationship between the liquid phase volume fraction and liquid phase velocity or pressure loss multiplier. The table data shows a good representation of the below.

Dependency of pressure drop on the water volume fraction

Dependency of drainage droplet size on the gas flow rate

Dehydration speed

In order to evaluate the obtained models, we calculated PEFC simulations with the models and validated the calculations.
In our simulator, in order to estimate the performance of PEFC cells taking all relevant transport phenomena (mass, chemical species, and heat) is solved on the coarse-grained mesh, coupled with electrochemical reactions. The mass transport equation is solved by Darcy’s law, using the distribution of the equivalent hydraulic parameter in flow channels estimated by detailed gas phase CFD. Here mass transport is coupled with heat and chemical species transport equations. Those all transport phenomena are coupled with electrochemical reactions in the MEA. Transport of chemical species and water through the MEA is also considered. Many engineering models are employed in order to consider various transport phenomena, like water up-take into electrolytes and effective transport of oxygen from the gas phase to reaction sites in catalyst layers, etc. Electrochemical reactions are modeled by the Butler-Volmer equation, in the manner of lumped parameter models.
The calculation using the derived two-phase model well reproduce the below phenomena.

Various Overpotentials difference between drive conditions

Drainage speed difference depending on gas flow rates

Liquid water difference between under the rib and the channel

Oxygen depletion depending on stoichiometry and liquid water distribution