Physics

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We show that the observed quark/lepton mass hierarchy can be realized dynamically on an interval extra dimension with point interactions. In our model, the positions of the point interactions play a crucial role in controlling the quark/lepton mass hierarchy and are determined by the minimization of the Casimir energy. By use of the exact extra-dimensional coordinate-dependent vacuum expectation value of a gauge-singlet scalar, we find that there is a parameter set, where the positions of the point interactions are stabilized and fixed, which can reproduce the experimental values of the quark masses precisely enough, while the charged lepton part is less relevant. We also show that possible mixings among the charged leptons will improve the situation significantly. © 2019 The Author(s) 2019. Published by Oxford University Press on behalf of the Physical Society of Japan.

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(SoNS) School of Natural Sciences

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Progress of Theoretical and Experimental Physics

Dynamical generation of quark/lepton mass hierarchy in an extra dimension

We have revisited the study of the nanostructured lithium iron silicate-based cathode for a safe lithium-ion battery and to understand the reaction mechanism from the first cycle to the second cycle. Ex situ Mössbauer and X-ray absorption near edge structure spectroscopy (XANES) measurements have been carried out on electrodes charged at various voltages to investigate the electrochemical activity of the Fe3+/Fe4+ redox couple to confirm the existence of Fe4+ and its role in defining the structural and electrochemical properties. The first charge and discharge lead to a structural change, which results in a potential plateau shift after the first charge. To validate this understanding, ex situ synchrotron X-ray diffraction (SXRD) along with Rietveld refinement results and first-principles density functional theory-based analysis have been performed, which also support the change in the crystal structure of the material with cycling. The in situ electrochemical impedance spectroscopy demonstrates phase transformation in delithiated iron silicate as lithium concentration changes during the charging process, which has been correlated with change in the density of states calculated by density functional theory. Finally, a full-cell prototype has been demonstrated for the first time using a lithium iron silicate cathode as the cathode and graphite as the anode, and this full cell showed a capacity retention of 92\% after 50 cycles at a 1 C rate. Copyright © 2019 American Chemical Society.

ACS Applied Energy Materials

Study of Higher Discharge Capacity, Phase Transition, and Relative Structural Stability in Li2FeSiO4 Cathode upon Lithium Extraction Using an Experimental and Theoretical Approach and Full Cell Prototype Study

Simultaneous superhydrophobic and visible range antireflective properties are demonstrated in hydrothermally grown ZnO nanorods (NRs) on chemically textured Si surfaces. A drastic transformation of Si micro-pyramids from hydrophobic to superhydrophobic is observed by securing the formation of polycrystalline ZnO NRs at surfaces, showing an increment of apparent contact angle from ∼102° to ∼157° and further explained in the light of a decrease in solid fractional surface area, according to the Cassie-Baxter model. Moreover, wurtzite phase of ZnO NRs is confirmed by the X-ray diffraction and Raman analysis. Such hierarchical structures further exhibit a large visible range antireflection (∼5\%), and correlated it to the variation in aspect ratio of Si pyramids in conjunction with the formation of graded refractive index. The combined superhydrophobic and large antireflection phenomena in the present dual-scale structures is believed to be useful for Si-based photovoltaic applications. © 2019 IOP Publishing Ltd.

Materials Research Express

Tailoring superhydrophobic ZnO nanorods on Si pyramids with enhanced visible range antireflection property

The large number of potential applications of ionic liquids (ILs) requires an understanding of their environmental impacts including their adverse effects on microorganisms living in soil and water. The molecular mechanism of toxic activities of these liquids is yet to be understood in detail. Any foreign molecules, interacting with an organism, have to encounter first the cellular membrane, which is predominantly composed of the lipid bilayer. In this work, multilamellar vesicles (MLV) of phospholipids have been used to shed light on the effect of an IL on the structure of a cellular membrane. The MLVs formed by the zwitterionic lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are found to shrink as a consequence of interaction with an imidazolium-based IL, 1-decyl-3-methylimidazolium tetrafluoroborate ([DMIM] [BF 4 ]). The absorbed ILs significantly modify the surface charge of the MLVs. While these observations indicate a strong membrane-IL interaction, synchrotron-based small angle X-ray diffraction (SAXD) measurements provide a structural description of the interaction. SAXD and Fourier transform infrared spectroscopy studies clearly reveal a disordering effect of the IL on the conformational organization of the lipid chains. The presence of the negatively charged lipid 1,2-dipalmitoyl-sn-glycero-3-phospho-l-serine sodium salt (DPPS) in MLVs plays an important role in disordering the chains in the membrane and inter-bilayer interactions. © 2018, European Biophysical Societies' Association.

European Biophysics Journal

Probing the effect of a room temperature ionic liquid on phospholipid membranes in multilamellar vesicles

A novel work on several aspects of current conduction mechanism for resistive switching (RS) of a reactive electrode-based memristor (Al/ZnO/Al) against generally used inert electrode-based devices has been illustrated. Compliance current (I cc ), i.e. maximum current through device and stop voltage (V stop ), i.e. maximum V stop upon device, has been used as bias characteristics to evaluate the effect upon conduction behavior. Effect of change in I cc for constant V stop and vice-versa upon high resistance state (HRS) and low resistance state (LRS) has been evaluated in terms of change in bulk defects, i.e. oxygen vacancy and interface inhomogenity, i.e. AlO x formation/dissolution. The device shows unipolar resistive switching (URS) at lower I cc (&lt; = 0.1 mA) and transits irreversibly into bipolar resistive switching (BRS) at higher I cc (&gt; = 1 mA). The dominant conduction behavior of the device is found to be homogenous resistive switching (HoRS). The conduction in HRS and LRS is found to be space-charge limited current conduction. Conductive atomic force microscopy results of the thin film switching layer support the HoRS mechanism and also illustrate the role of interfacial oxide in attributing BRS behavior in the Al/ZnO/Al resistive switch. Studies can be utilized in future to further understand the RS conduction mechanism in reactive electrode-based RS and can be applied for multi-state memory applications. © 2019 IOP Publishing Ltd.

Semiconductor Science and Technology

Resistive switching in reactive electrode-based memristor: Engineering bulk defects and interface inhomogeneity through bias characteristics

Prediction of crystal structure and study of transport and optoelectronic properties of NH2 substituted trans-stilbene derivative: A new promising ambipolar organic semiconductor

A lightweight organic material, trans-4′-dimethylamino-4-nitro-α-cyanostilbene, exhibits notable charge carrier mobility (∼10 -4 cm 2 V -1 s -1 ). The non-centrosymmetric material also displays moderate second harmonic generation activity. This is one of the rarest examples of small organic materials displaying semiconductor characteristics. The charge-transfer pathway as elucidated via high-resolution single-crystal X-ray diffraction data based "energy frameworks" and "experimental charge density" analyses is assessed by measuring the charge carrier mobility using the space charge limited current technique on pure single-crystal diode devices. These advanced structural analyses clearly demonstrate that charge transport in organic crystals is purely governed by its molecular packing, especially the π-π stacking geometry. The balanced ambipolar charge transport behavior makes this highly soluble and thermally stable organic crystal promising for applications in optoelectronic devices. Moreover, this report introduces the crucial role of energy frameworks and charge density analyses for fundamental understanding of the structure-property relationship in organic semiconductors. Copyright © 2019 American Chemical Society.

Chemistry

Crystal Growth and Design

Structure-Property Relationship in an Organic Semiconductor: Insights from Energy Frameworks, Charge Density Analysis, and Diode Devices

Ever since the discovery of two-dimensional (2D) material graphene, there has been huge interest in the exploration of low-dimensional materials that can be exfoliated from their three-dimensional counterpart with enriched properties due to quantum confinement. Two members of the Sn-S family, Pnma-SnS and P3Im1-SnS 2 that possess a layered structure with 2D nanosheets stacked via weak van der Waals (vdW) interactions, have widely been studied in this regard. The other member, Pnma-Sn 2 S 3 , comprising one-dimensional (1D) nanochains bound via vdW interactions, has never been investigated in the view of exfoliated 1D analogue. In this work, we therefore comprehensively studied 1D-Sn 2 X 3 (X = S and Se) nanochains and demonstrated them to be stable and exfoliable from their bulk counterpart. Further, it is also shown that the exfoliated 1D nanochains can easily be identified from their bulk counterpart using Raman, infrared, and X-ray spectroscopies. Our calculations predict a direct band gap of 2.35 eV (1.67 eV) for 1D-Sn 2 S 3 (1D-Sn 2 Se 3 ) nanochains under the Heyd, Scuseria, and Ernzerhof functional, with a broad absorption region lying between 2 and 8 eV, lower reflection, high charge-carrier mobility with ambipolar characteristics, as well as a larger value of the Seebeck coefficient and a smaller value of the thermal conductivity, resulting in a better thermoelectric figure of merit. These interesting electronic, optical, transport, and thermoelectric properties make 1D-Sn 2 X 3 nanochains a potential candidate for the application in future optoelectronic and thermoelectronic devices, in fact, better than three-dimensional (3D)-Sn 2 X 3 for few of the applications. Moreover, 3D-Sn 2 Se 3 is also investigated in detail in this work, which to the best of our knowledge has not been done before. © 2019 American Chemical Society.

ACS Applied Materials and Interfaces

One-Dimensional-Sn 2 X 3 (X = S, Se) as Promising Optoelectronic and Thermoelectronic Materials: A Comparison with Three-Dimensional-Sn 2 X 3

Charge transport properties of common donor copolymers in organic photovoltaics, poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7-Th), with molecular structures differing only in the pendant group, are studied. This is the first report of field-effect transistor mobility (µ FET ) of PTB7-Th (0.14 cm 2 V −1 s −1 ) and the highest µ FET for PTB7 (0.01 cm 2 V −1 s −1 ). µ FET of PTB7-Th is found to be almost one order of magnitude higher than PTB7. To understand the influence of molecular structure on charge transport, hole reorganization energy (λ h ) is calculated from first-principles. λ h of PTB7-Th (≈150 meV) is found to be lower than PTB7 (≈346 meV). Further, the ratio of hopping rate versus square of charge transfer integral calculated from Marcus theory using λ h for these systems is found to indicate a higher rate of hole transfer across dimers or homojunction interface for PTB7-Th. These results are supplemented by experimentally determined λ using bulk-heterojunction organic solar cells, where λ PTB7-Th ≈200 meV and λ PTB7 ≈310 meV follow a similar trend. The effective hole-mobility estimation from BHJ devices correlates well with these λ values. This study provides understanding of charge transport properties via reorganization energy, as a function of pendant group without altering the backbone of the chains. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Functional Materials

Influence of Pendant Group on Mobility of Organic Thin Film Transistor in Correlation with Reorganization Energy of Molecules

We propose a new form of Lagrangian that shows branching for the associated Hamiltonian and has relevance to the quadratic type and mixed linear-quadratic Liénard-type nonlinear dynamical equations on adjusting the underlying parameters. Non-uniqueness of the Lagrangian is pointed out and a particular one when Fourier transform is demonstrated to depict a momentum-dependent quantum-like mass system when expanded binomially. © 2019 World Scientific Publishing Company.