Effect of Graphene/TiO2 (001) Interface on Threshold Voltage and Nonlinearity

NANO ◽  
2018 ◽  
Vol 13 (06) ◽  
pp. 1830004 ◽  
Author(s):  
Yuehua Dai ◽  
Shanshan Gong ◽  
Zhisheng Zhong ◽  
Fengyu Gao ◽  
Feifei Wang ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Threshold Voltage ◽  
Density Functional ◽  
Tight Binding ◽  
Resistive Transition ◽  
Design And Optimization ◽  
Interface Barrier ◽  
Iv Curves ◽  
Energy Package

In this work, the threshold voltage ([Formula: see text]) and nonlinearity (NL) of Graphene (Gra)/TiO2/Gra heterojunction were studied. First, the density functional tight binding (DFTB[Formula: see text]) and much more dynamics were used to investigate the IV curves and the resistive switching properties of TiO2 slab and Gra/TiO2/Gra heterojunction. The NL of Gra/TiO2/Gra heterojunction is stronger than that of the TiO2 slab. The [Formula: see text] of the resistive transition of the heterojunction is larger than that of the TiO2 slab. The tunneling probabilities and the Mulliken atomic population at the Gra/TiO2 interface under different electric fields were calculated by the Cambridge sequential total energy package (CASTEP). Results showed that both the parameters evidently increased under a certain numerical electric field. Finally, the movement of atom in the electric field and the change in the chemical bond were simulated by DFTB[Formula: see text] module. The effect of the Gra/TiO2 interface on [Formula: see text] and NL was further illustrated. Postponed [Formula: see text] and improved NL were found at the heterojunction relative to the TiO2 slab due to the presence of the interface barrier. This work provides guidance and reference for design and optimization of TiO2-based selectors.

Molecular Electronics Including Temperature Effects Based on Dyes Pigments

2019 ◽  
Vol 19 (6) ◽  
pp. 3631-3636
Author(s):  
Adriana T Amador ◽  
Abel F. G Neto ◽  
Jorddy N Cruz ◽  
Fatima N. B Magno ◽  
Francisco C Marques ◽  
...  
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Molecular Electronics ◽  
Electric Fields ◽  
Density Functional ◽  
Functional Theory ◽  
Degradation Temperature ◽  
Red Color ◽  
The Density Functional Theory ◽  
Almost All

In this work we used the Density Functional Theory to study the thermodynamic properties from Brazilein (BZE) and Brazilin (BZI) molecules, main pigments responsible for the red color from Brazil wood. We did a comparison between the two dyes to then know which dye has better resistance to temperature (T ) and external electric field (E) values, aiming their potential to possible applications in solar cells, as excitons trainers. We have found that the BZE molecule becomes less stable after a temperature known as degradation temperature, and therefore enters oxidation state. However, BZE is more stable and more resistant to high temperatures. With respect to the applied external electric field, we find that BZE is more reactive to almost all the applied electric fields, thus more easily converted into energy in the form of electrical work.

Dielectrophoretic Control of a Droplet at the Interface of Two Liquids in a Three Liquid System

2018 ◽  
Author(s):  
Manoj Lokanathan ◽  
Enakshi Wikramanayake ◽  
Vaibhav Bahadur ◽  
Roger Bonnecaze
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Threshold Voltage ◽  
Water Droplet ◽  
Critical Size ◽  
Silicone Oil ◽  
Liquid System ◽  
Interfacial Phenomena ◽  
Immiscible Liquids ◽  
Voltage Dependent

The influence of an electric field on a water droplet resting at the interface of two immiscible liquids is studied experimentally and theoretically. The droplet is initially in a state of equilibrium due to the balance between gravitational, buoyancy and capillary forces. Application of an electric field across the droplet-interface system disturbs the equilibrium. The electrical force increases the immersion angle of the droplet and eventually causes it to ‘sink’ when a critical immersion angle is reached. Experiments are conducted with a deionized water droplet, resting at the interface of silicone oil and sunflower oil. Experiments involve the application of an electric field and image analysis to track the voltage dependent immersion angle. The objective is to determine the threshold voltage at which the droplet sinks. Experiments are complemented by an analytical model that balances gravity, buoyancy, capillary, and dielectrophoretic forces to predict the change in the position of the droplet and the immersion angle. Experiments and analysis were conducted for Bond numbers ranging from 0.1 to 1.7, the latter being the critical size at which a droplet will ‘sink’ due to its weight. The predicted immersion angles and threshold voltage show a good match to the experimental measurements. Overall, this work highlights the utility of electric fields to control interfacial phenomena at the interface of two immiscible liquids.

scholarly journals Quantum-confinement and Structural Anisotropy result in Electrically-Tunable Dirac Cone in Few-layer Black Phosphorous

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Kapildeb Dolui ◽  
Su Ying Quek
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Fields ◽  
Quantum Confinement ◽  
Density Functional ◽  
Black Phosphorus ◽  
Spin Orbit ◽  
Dirac Cone ◽  
Structural Anisotropy ◽  
Interaction Term

Abstract Two-dimensional (2D) materials are well-known to exhibit interesting phenomena due to quantum confinement. Here, we show that quantum confinement, together with structural anisotropy, result in an electric-field-tunable Dirac cone in 2D black phosphorus. Using density functional theory calculations, we find that an electric field, E ext, applied normal to a 2D black phosphorus thin film, can reduce the direct band gap of few-layer black phosphorus, resulting in an insulator-to-metal transition at a critical field, E c . Increasing E ext beyond E c can induce a Dirac cone in the system, provided the black phosphorus film is sufficiently thin. The electric field strength can tune the position of the Dirac cone and the Dirac-Fermi velocities, the latter being similar in magnitude to that in graphene. We show that the Dirac cone arises from an anisotropic interaction term between the frontier orbitals that are spatially separated due to the applied field, on different halves of the 2D slab. When this interaction term becomes vanishingly small for thicker films, the Dirac cone can no longer be induced. Spin-orbit coupling can gap out the Dirac cone at certain electric fields; however, a further increase in field strength reduces the spin-orbit-induced gap, eventually resulting in a topological-insulator-to-Dirac-semimetal transition.

Calculation of Carrier Mobility in Copper Phthalocyanine by Simple Hopping Model

2016 ◽  
Vol 675-676 ◽  
pp. 3-6
Author(s):  
Surachai Pengmanayol ◽  
Janit Girdpun
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Carrier Mobility ◽  
Density Functional ◽  
Copper Phthalocyanine ◽  
Functional Theory ◽  
Charge Transfer Rate ◽  
Transfer Integral ◽  
Hopping Model

The Monte Carlo approach is used to calculate carrier mobility in molecular copper phthalocyanine (CuPc) with applied electric field in the range of 0.5 to 20 × 103 kV/cm. Density functional theory (DFT) is employed to derive the molecular interaction between neighboring molecules with various applied electric fields. The result of DFT calculation to evaluate transfer integral that used to calculate hopping rate in the range of applied electric fields. The charge transfer rate between adjacent molecules can be estimated by using the Marcus–Levich–Jortner (MLJ) formalism. The charge is assumed to be localized on the donor and then transferred to the acceptor. Tunneling is modeled by including selected vibration modes at the quantum mechanical level. The result of hopping rate is in ordered of 1015 s-1 for hole hopping in direction of applied electric field on the contrary hopping rate in ordered of 1014 s-1. The result of mobility can be calculated in range of 0.44 - 10.0 cm2/Vs decrease as a function of applied electric field that calculated by simple hopping model.

Pool-Frenkel effect and high frequency dielectric constant determination of semiconducting P2O5-Li2MoO4-Li2O and P2O5-Na2MoO4-Na2O bulk glasses

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Dariush Souri ◽  
Mohammad Elahi ◽  
Mohammad Yazdanpanah
Keyword(s):  
Dielectric Constant ◽  
Electric Field ◽  
Electric Fields ◽  
Threshold Voltage ◽  
High Frequency ◽  
Strong Electric Field ◽  
Nonlinear Effects ◽  
High Frequency Dielectric Constant ◽  
Conduction State ◽  
Current Voltage

AbstractThe ternary 70P2O5-10Li2MoO4-20Li2O and 70P2O5-10Na2MoO4-20Na2O glasses, prepared by the press-melt quenching technique, were studied at temperatures between 298 and 418 K for their high dc electric field properties. For the above purpose, the effect of a strong electric field on the dc conduction of these amorphous bulk samples was investigated using the gap-type electrode configuration. At low electric fields, the current-voltage (I — V) characteristics have a linear shape, while at high electric fields (> 103 V/cm), bulk samples show nonlinear effects (nonohmic conduction). Current-voltage curves show increasing departure from Ohm’s law with increasing current density, leading to critical phenomena at a maximum voltage (threshold voltage), known as switching (switch from a low-conduction state to a higher-conduction state at threshold voltage). The Pool-Frenkel high-field effect was observed at electrical fields of about 103–104 V/cm; then the lowering factor of the potential barrier, the high frequency dielectric constant, and the refractive index of these glasses were determined.

scholarly journals Influence of Electric Field in the Adsorption of Atomic Hydrogen on Graphene

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
C. Cab ◽  
R. Medina-Esquivel ◽  
C. Acosta ◽  
J. Mendez-Gamboa ◽  
F. Peñuñuri ◽  
...  
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Electric Fields ◽  
Atomic Hydrogen ◽  
Density Functional ◽  
Electronic Charge ◽  
Generalized Gradient ◽  
Electronic Charge Density ◽  
System A ◽  
Spin Polarized

The influence of external electric field (EF) in the adsorption of atomic hydrogen on graphene (H/G) was studied by means of electronic structure calculations based on spin-polarized density functional theory with generalized gradient approximation (GGA). The changes in atomic hydrogen physisorption-chemisorption on graphene owed to EF (which ranged between −1.25 V/Å and 0.75 V/Å) were determined. Analysis of the electronic charge density for an H/G system explained the EF influences on the adsorption properties (analyzing changes in electronic charge density for H/G system). A decrease of more than 100% in the chemisorption barrier for an EF of −1.25 V/Å was found. The changes in the electronic charge density confirm the possibility of manipulating the physical-chemical adsorption of hydrogen on graphene by applying electric fields.

Density functional theory study of electric field effects on the isomerization of a photochromic molecular switch based on 1,2-dithienylethene

2014 ◽  
Vol 92 (4) ◽  
pp. 317-323 ◽  
Author(s):  
Ehsan Zahedi ◽  
Majid Mozaffari ◽  
Fereshteh-Sadat Karimi ◽  
Azita Nouri
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
Closed Form ◽  
External Electric Field ◽  
Electric Fields ◽  
Density Functional ◽  
Open Form ◽  
Functional Theory ◽  
External Electric Fields ◽  
Homo Lumo

Structural and electronic properties of 1,2-bis(5-methyl-[2,2′-bithiophen]-4-yl)cyclopent-1-ene in closed form and open form under various external electric field with strengths, 0, 10 × 10−4, 20 × 10−4, 30 × 10−4, 40 × 10−4, and 50 × 10−4 a.u., were studied using the DFT-B3LYP/6-31G* method. As a positive index, structural parameters, length of the photoisomers, and the electronic spatial extents are almost stable at different external electric fields. The UV-Vis electronic spectrum based on time-dependent density functional theory indicated that the HOMO → LUMO transition in the closed form under different electric field strengths is strongly allowed, whereas is very weak in the open form. Electronic response parameters such as the HOMO−LUMO gap, electric dipole moment, and polarizability showed that electric conductivity of the closed form at different field strengths is greater than in the open form. Results of electronic density of states show that at high external electric field, the conductivity of the open form and closed form will be probably equal and switching behavior cannot be observed. Isomerization of the closed form to the open form at different external electric fields can be considered as exothermic and spontaneous.

BLOCH DYNAMICS IN SPATIALLY LOCAL INHOMOGENEOUS ELECTRIC FIELDS

2001 ◽  
Vol 11 (02) ◽  
pp. 425-453
Author(s):  
JOSEPH P. REYNOLDS ◽  
GERALD J. IAFRATE ◽  
JUN HE
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Nearest Neighbor ◽  
Constant Electric Field ◽  
Tight Binding ◽  
Homogeneous Field ◽  
Wannier Functions ◽  
Field Dependent ◽  
Bloch Electrons ◽  
Special Case

The influence of local inhomogeneities on the electric field dependent properties of Bloch electrons is studied. The homogeneous electric field is described through the use of the vector potential, and the instantaneous Wannier functions of the homogeneous field dependent Hamiltonian are used as bases states to depict Bloch dynamics and properties. Model examples are treated using Slater-Koster inhomogeneities and nearest-neighbor tight-binding band structure in a one dimensional, single-band analysis. Detailed analysis is presented for the special case of a constant electric field; here the influence of localization due to the presence of the electric field is shown to clearly affect the energy spectrum of the Bloch electron for a single and double impurity configuration.

Dynamic Simulation of the Migration of Oxygen Vacancy Defects in Rutile TiO2

2012 ◽  
Vol 1430 ◽  
Author(s):  
Jan M. Knaup ◽  
Michael Wehlau ◽  
Thomas Frauenheim
Keyword(s):  
Oxygen Vacancy ◽  
Dynamic Simulation ◽  
Electric Fields ◽  
Density Functional ◽  
Diffusion Processes ◽  
Tight Binding ◽  
Dynamic Simulations ◽  
Vacancy Defects ◽  
Barrier Heights ◽  
Large Dielectric Constant

ABSTRACTWe simulate the thermodynamics and kinetics of the drift/diffusion of oxygen vacancy defects in rutile TiO2, using the density-functional based tight-binding (DFTB) method. Both static and dynamic simulations have been performed. Results indicate that DFTB is well suited to examine the dynamic behavior of oxygen vacancies in TiO2. Detailed analysis shows, that strong model size dependence in relative diffusion barrier heights between different diffusion processes requires great care in defect diffusion simulations in TiO2. Thermodynamic results on the influence of an external electric field show that, due to the large dielectric constant, the coulomb driving force on oxygen vacancy diffusion is very small. Dynamic simulation of the influence of electric fields on the diffusion requires the use of advanced molecular dynamics acceleration schemes.

scholarly journals Directing isomerization reactions of cumulenes with electric fields

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yaping Zang ◽  
Qi Zou ◽  
Tianren Fu ◽  
Fay Ng ◽  
Brandon Fowler ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Scanning Tunneling Microscope ◽  
Lower Energy ◽  
Density Functional ◽  
Energy Transition ◽  
Isomerization Reaction ◽  
Scanning Tunneling ◽  
Trans Form ◽  
Functional Theory

Abstract Electric fields have been proposed as having a distinct ability to catalyze chemical reactions through the stabilization of polar or ionic intermediate transition states. Although field-assisted catalysis is being researched, the ability to catalyze reactions in solution using electric fields remains elusive and the understanding of mechanisms of such catalysis is sparse. Here we show that an electric field can catalyze the cis-to-trans isomerization of [3]cumulene derivatives in solution, in a scanning tunneling microscope. We further show that the external electric field can alter the thermodynamics inhibiting the trans-to-cis reverse reaction, endowing the selectivity toward trans isomer. Using density functional theory-based calculations, we find that the applied electric field promotes a zwitterionic resonance form, which ensures a lower energy transition state for the isomerization reaction. The field also stabilizes the trans form, relative to the cis, dictating the cis/trans thermodynamics, driving the equilibrium product exclusively toward the trans.

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