Metal nanowire–polymer matrix hybrid layer for triboelectric nanogenerator

摘要： In this work, we studied the surface potential of a metal–polymer hybrid layer and its effect on the performance of a triboelectric nanogenerator (TENG). Ag nanowires (AgNWs) separately embedded in two different polymers–one with a positive tribopotential and the other with a negative tribopotential–were prepared as model hybrid systems. The surface potentials of the hybrid system were systematically investigated by Kelvin probe force microscopy. The results demonstrated that each component of the hybrid layer affected the other component because of the difference in their work functions. The following two important findings were obtained. First, the surface potential of each polymer shifted drastically toward that of Ag and the surface potential of Ag shifted toward that of each polymer. Second, higher density of AgNWs led to higher Ag-induced charge density in the polymer, which consequently resulted in larger shift in the surface potential of the polymer. TENG performance measurements revealed that the tribopotential difference between the contact surfaces of the AgNW–polymer hybrid layer and the perfluoroalkoxy alkane (or Nylon) used as the top triboelectric layer governed the TENG performance. Our systematic investigation of the surface potential of a hybrid surface consisting of two materials with different surface potentials provides insight into the design of triboelectric layers for high-performance TENGs.

Ca and S <i>K</i> -edge XANES of CaS calculated by different methods: influence of full potential, core hole and Eu doping

摘要： Ca and S K-edge spectra of CaS are calculated by the full-potential Green’s function multiple-scattering method, by the FLAPW method and by the finite-difference method. All three techniques lead to similar spectra. Some differences remain close to the edge, both when comparing different calculations with each other and when comparing the calculations with earlier experimental data. Here it is found that using the full potential does not lead to significant improvement over the atomic spheres approximation and that the effect of the core hole can be limited to the photoabsorbing atom alone. Doping CaS with Eu will not affect the Ca and S K-edge XANES of CaS significantly but may give rise to a pre-edge structure not present for clean CaS.

A Surface Potential Based Model for Dual Gate Bilayer Graphene Field Effect Transistor Including the Capacitive Effects

摘要： In this work, a surface potential modeling approach has been proposed to model dual gate, bilayer graphene field effect transistor. The equivalent capacitive network of GFET has been improved considering the quantum capacitance effect for each layer and inter-layer capacitances. Surface potentials of both layers are determined analytically from equivalent capacitive network. The explicit expression of drain to source current is established from drift-diffusion transport mechanism using the surface potentials of the layers. The drain current characteristics and transfer characteristics of the developed model shows good agreement with the experimental results in literatures. The small signal parameters of intrinsic graphene transistor i.e. output conductance (gds), trans-conductance (gm), gate to drain capacitance (Cgd) and gate to source capacitance (Cgs) have been derived and finally, the cut-off frequency is determined for the developed model. The model is compared with reported experimental data using Normalised Root Mean Square Error (NRMSE) metric and it shows less than 16% NRMSE. A Verilog-A code has been developed for this model and a single ended frequency doubler has been designed in Cadence design environment using this Verilog-A model.

Mechanistic Study on Facet-Dependent Deposition of Metal Nanoparticles on Decahedral-Shaped Anatase Titania Photocatalyst Particles

摘要： Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density on {001} and {101} and comparing with the results of deposition from colloidal metal particles in the dark (CDD) or under photoirradiation (CDL). The observed facet selectivity, more or less {101} preferable, depended mainly on pH of the reaction suspensions and was almost non-selective at low pH regardless of the deposition method, PD or CDL, and the metal-source materials. Based on the results, the present authors propose that facet selectivity is attributable to surface charges (zeta potential) depending on the kind of facets, {001} and {101}, and pH of the reaction mixture and that this concept can explain the observed facet selectivity and possibly the reported facet selectivity without taking into account facet-selective reaction of photoexcited electrons and positive holes on {101} and {001} facets, respectively.

26.1%-efficient POLO-IBC cells: Quantification of electrical and optical loss mechanisms

摘要： We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly‐Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p‐type FZ wafer and 24.6% on a 2 Ω cm n‐type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current‐voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly‐Si region to be in the range from 13 to 21 cm s?1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s?1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s?1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process‐induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).

Potential Dependence of Mechanical Stability and Electronic Coupling of Single S-Au Bonds

摘要： Providing a mechanically stable and electronically efficient coupling between a molecule and an electrode is critical to the study of charge transfer and conductance of the molecule. A common method is to link the molecule to Au electrodes via a linker (e.g., thiol terminal of the molecule). Here we study the mechanical stability and electronic coupling of S-Au bond in single molecule junctions over a broad range of electrode potential. Our results show that the mechanical and electromechanical properties of molecule-electrode contact undergo a systematic change with the potential involving Au oxidation at positive potentials and S protonation at negative potentials. The study establishes the potential range for a stable S-Au bond and determines the potential dependence of the mechanical and electromechanical properties of the molecule-electrode contact, which is crucial to the interpretation of potential dependent charge transfer in electrochemistry and electrochemical gating of charge transport in molecular electronics.

A thermodynamic potential for barium zirconate titanate solid solutions

摘要： Barium zirconate titanate [Ba(ZrxTi1?x)O3] solid solutions are promising lead-free ferroelectric materials that have received substantial interest. Thermodynamic analysis based on phenomenological Landau–Devonshire theory is a powerful method for theoretical investigation of ferroelectric materials, but cannot be applied to Ba(ZrxTi1?x)O3 because there is no thermodynamic potential. In this paper, a thermodynamic potential for Ba(ZrxTi1?x)O3 (0 ≤ x ≤ 0.3) solid solutions is constructed, and then a thermodynamic analysis carried out. The results accurately reproduce known phase structures and their transition temperatures, with good agreement with experimentally measured polarization, dielectric, and piezoelectric constants. It is found that Ba(ZrxTi1?x)O3 solid solutions at room temperature have three phase boundaries, including a tetragonal–orthorhombic phase boundary at x = 0.013, an orthorhombic–rhombohedral phase boundary at x = 0.0798, and a rhombohedral–paraelectric phase boundary at x = 0.2135. The results also indicate that the chemical composition-induced ferroelectric–paraelectric phase boundary has superior electromechanical properties, suggesting a new way to enhance electromechanical coupling in Ba(ZrxTi1?x)O3 solid solutions.

Handbook of Materials Modeling (Applications: Current and Emerging Materials) || Incorporating Electronic Effects in Molecular Dynamics Simulations of Neutron and Ion-Induced Collision Cascades

摘要： Molecular dynamics offers an ideal method for investigating the evolution of collision cascades and the formation of the resulting primary radiation damage. However, several modifications to classical molecular dynamics are needed in order to facilitate simulating the highly non-equilibrium cascade process. One such modification, which is still a point of active research, concerns methods by which electronic effects, which are expected to be important in collision cascades, can be included in molecular dynamics simulations, where a priori atoms are treated as classical particles and electrons are only present implicitly through the atomic interactions represented by the interatomic potential. This chapter describes current methods by which electronic effects can be accounted for in cascade simulations, with special focus on the developments in the field that have taken place over the last 10 years.

[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field Emitted Current from a Paraboloidal Nano-Emitter Using its Exact Eigenstates and a Three- Dimensional WKB Expression for the Transmission Coefficient

Electromagnetic engineered mechanical trapping potential and the conversion in optomechanics

摘要： The manipulation of mechanical response in optomechanical system allows observation of quantum behavior by cooling a mechanical resonance to its quantum mechanical ground state, and it relies on the effective tuning of trapping potentials. In this work, we investigate the conversion process between radiation pressure and mechanical trapping potential which is engineered by the optical field in an optomechanical system. Moreover, a set of trapping potentials could be achieved by tuning the system, such as detuning, pumping power and decay rates. Specifically, the speed of conversion between different potential states is studied which approaches the megahertz level.