Enhancement Of Polarizability Research Articles

Na+ doped CuO: A new paradigm electrode material for high performance supercapacitors

This study investigates the influence of sodium doping on the properties of cupric oxide (CuO) thin films synthesized via spray pyrolysis. Comprehensive characterization was conducted using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, Hall effect measurements, and electrochemical studies. All films exhibited p-type conductivity, with an optical band gap variation from 1.53 to 1.73 eV. XRD analysis confirmed the dominance of monoclinic CuO, with minor phases of Cu2O and Cu4O3. EDAX and XPS verified the incorporation of Cu, O, and Na elements. FESEM revealed a densely packed morphology with uniform particle distribution and rough surfaces in the electrically optimized film. The Raman spectra of doped samples showed increased intensity and sharpness, attributed to Na+ ion-induced polarizability enhancement. Hall effect measurements indicated a tenfold decrease in carrier concentration and a more than tenfold increase in mobility upon sodium doping. Films doped with 4 at.% sodium exhibited the lowest resistivity. Additionally, Na doping enhanced the electrochemical performance of CuO. These findings demonstrate that sodium doping significantly enhances the electrical, optical and electrochemical properties of CuO thin films, making them suitable for applications in optoelectronic devices and supercapacitors.

Enhanced near-infrared femtosecond nonlinear optical properties in zinc borate glasses activated with Er2O3

Several advanced materials have been investigated for nonlinear optical device applications. However, oxide glasses are competing materials in contrast to those advanced materials due to ease of preparation in three dimensions with diverse shapes along with flexibility in choosing the composition which is essential to tune the nonlinear optical features for specific applications. Doping rare-earth ions is one of the methods used to tune the nonlinear optical features of glass specimens, and it has been explored extensively in recent years. Using femtosecond laser pulses, the effect of Er2O3 concentration on nonlinear optical characteristics such as nonlinear absorption, nonlinear refraction, and optical limiting qualities was investigated using the Z-scan approach. The dual photon absorption and self‒focusing refraction nonlinear magnitudes are improved as the function of Er2O3 content owing to the formation of non‒bridging oxygens and enhancement in polarizability of glasses while the optical limiting features were decreased. These nonlinear absorptions and optical limiting results endorse the high Er2O3 loaded glasses are beneficial for nonlinear photonic devices functioning in the near-infrared regions.

Effects of material texture and packing density on the interfacial polarization of granular soils

Many electrical and electromagnetic (EM) methods operate at MHz frequencies, at which the interfacial polarization occurring at the solid-liquid interface in geologic materials may dominate the electrical signals. To correctly interpret electrical/EM measurements, it is therefore critical to understand how the interfacial polarization influences the effective electrical conductivity and permittivity spectra of geologic materials. We have used pore-scale simulation to study the role of material texture and packing in interfacial polarization in water-saturated granular soils. Synthetic samples with varying material textures and packing densities are prepared with the discrete element method. The effective electrical conductivity and permittivity spectra of these samples are determined by numerically solving the Laplace equation in a representative elementary volume of the samples. The numerical results indicate that the effective permittivity of granular soils increases as the frequency decreases due to the polarizability enhancement from the interfacial polarization. The induced permittivity increment is mainly influenced by the packing state of the samples, increasing with the packing density. Material textures such as the grain shape and size distribution may also affect the permittivity increment, but their effects are less significant. The frequency characterizing the interfacial polarization (i.e., the characteristic frequency) is mainly related to the electrical contrast of the solid and water phases. The model based on the traditional differential effective medium (DEM) theory significantly underestimates the permittivity increment by a factor of more than two and overestimates the characteristic frequency by approximately 1 MHz. These inaccurate predictions are due to the fact that the electrical interactions between neighboring grains are not considered in the DEM theory. A simple empirical equation is suggested to scale up the theoretical depolarization factor of grains entering the DEM theory to account for the interaction of neighboring grains in granular soils.

Enhanced non-linear optical properties of Eu3+ activated glasses by embedding silver nanoparticles

Tri-positive lanthanide ion (Eu3+) activated glasses doped with different concentrations of silver (Ag0) nanoparticles obtained using thermal reducing agent were fabricated by applying the method of melt quench. The formation of Ag0 nanoparticles in glasses was revealed by the surface plasmon resonance (SPR) peak in the absorption spectra. Transmission electron microscopic measurements confirmed the presence of spherically shaped Ag0 nanoparticles of different size distribution. The absorption spectra showed a red–shift of the SPR peak with an increase in AgNO3 concentration occurring through Ostwald's ripening process because of the growth of particle size (as evidenced from microscope images). The non-linear optical (NLO) and optical limiting measurements were performed in the near infrared spectral region and femtosecond pulse excitation. The non-linear parameters were found to increase as the AgNO3 concentration increased to 0.6 mol %, however, the parameters subsequently decreased at higher doping level. The optical limiting threshold values demonstrated a reverse trend. The increase in non-linear optical properties regarding Ag nanoparticles concentration attributed to the enhancement of polarizabilities of glasses that occurred through local field stimulated by SPR of Ag nanoparticles when exposed to laser radiation of high energy. The increase in NLO coefficients (particularly the non-linear absorption coefficient) and the decrease in optical limiting threshold values with AgNO3 concentration (up to 0.6 mol %) indicated that these glasses containing 0.6 mol % AgNO3 are useful for the construction of the power optical limiters that function at the infrared region in the femtosecond pulse regime.

Cu-doped ZnO synthesis by ionothermal method: Morphology and optical properties

Zinc oxide (ZnO) and Cu-doped ZnO nanostructures having different morphologies such as nanorod, nanosheet and flower like have been synthesized via a one-step, eco-friendly ionothermal synthetic method at ambient pressure using [OMIM]Br and [C8DABCO]Br ionic liquids in terms of solvent and template. The dopant contents in the samples were 3%. The synthesized nanomaterials were examined by using scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Visible absorption spectroscopy, and Z-scan technique. The results show that ILs and Cu2+ play on significant role on morphology of nanostructures. The average crystal size of ZnO was found to be in the range of 15.5–17 nm. Also doped in different ILs are effect on bandgap of products. The third order nonlinear absorption coefficient and refractive index were calculated and increased due to the enhancement of polarizability by the doping ions (Cu2+). Open and closed aperture of Z-scan method revealed two photon absorption and self-focusing (n2 > 0) effect in the samples. Third order nonlinear susceptibility of samples is in order of 10−7(cm2/W). As a result, Cu dopant of ZnO samples are more effective than their morphology in nonlinear coefficient results. The synthesized samples are proposed as a new-type nonlinear optical materials for optical applications.

Tunable optical linear&nonlinear, magnetic and Faraday rotation properties: Comparison of ZnO based DMSs alloys in diamagnetic solid matrix

Diluted magnetic semiconductors (DMSs) doped glasses are attractive to magneto-optical and nonlinear applications due to the sp-d exchange interaction between semiconductor carriers and magnetic ions in glass matrix. This paper reports the synthesis, characterization and doping of ZnO, Zn0.96Mn0.04O and Zn0.6Cu0.4O in heavy metal oxides homogeneous matrix. Mn2+ and Mn3+ co-existed in Zn0.96Mn0.04O while only Cu+ existed in Zn0.6Cu0.4O which occupied or entered into the interstitial of Zn2+ sites, resulting the increase of lattice spacing and newly Raman vibration mode at 526.9 cm−1 and 571 cm−1. Due to the large incorporation concentration of Cu, Zn0.6Cu0.4O presented ZnO and Cu2O crystallites. Due to the s–d and p–d exchange interactions of doped ions, Zn0.96Mn0.04O and Zn0.6Cu0.4O showed decreased energy band gap, characteristic transition of Mn2+, Mn3+ and Cu+ ions and ferromagnetic magnetization.The influence of DMSs to the homogeneity, color and structure of heavy metal oxide glasses is apparent. Zn0.96Mn0.04O doping caused slightly crystallization of cubic Bi2O3. FT-IR displayed the network former role of ZnO as ZnO4 units and the modification of Mn2+, Mn3+, and Cu+, Cu2+ to the frame units of PbO4, BiO3, BiO6, BO3 in glass. DMSs doped glasses all exhibited red-shift of cutoff wavelength, shrinkage of energy band gap, electron transition and luminescence of Mn and Cu ions. The third order nonlinear absorption coefficient and refractive index were calculated and increased due to the enhancement of polarizability by the doping ions. even though Zn0.96Mn0.04O and Zn0.6Cu0.4O doped glasses showed superfine structures in EPR spectra, all glasses displayed diamagnetic behavior and the Zn0.6Cu0.4O doped glass showed the highest magnetization and Verdet constant (0.2524 min/G.cm at 500 nm wavelength) which is attractive for photonics, nonlinearity and Faraday rotation applications.

Dissecting energy level renormalization and polarizability enhancement of molecules at surfaces with subsystem TDDFT

Molecules in the vicinity of extended systems, such as metal surfaces, behave in peculiar ways. Their energy levels are broadened, and their molecular properties are so profoundly enhanced that they hardly resemble the ones of the isolated molecule. This is due to dynamical interactions (i.e., interactions that couple excited electronic states) between the molecular, finite system and the extended, infinite system. Since the early days of quantum mechanics, Fermi golden rule has been employed to explain some of the dynamical interactions (such as the broadening of the energy levels). However, a fully quantum-mechanical and ab initio model of these systems remains elusive, in most part due to the computational complexity entailed in the simulations. In this work, we present subsystem time-dependent DFT (TDDFT) simulations of water and benzene molecules as they interact with surfaces of MoS2 monolayer and Au(111). A many-body expansion of the supersystem response function in terms of molecule and surface responses allows us to dissect and describe the dynamical interactions. Not only do we compute and clearly identify terms related to dissipation, broadening, and peak shift, but we also provide a connection between subsystem TDDFT and Fermi golden rule. This work sets the stage for subsystem TDDFT simulations of interfaces relevant to energy materials and nonadiabatic dynamics at such interfaces.

Dipole polarizability of nanodiamonds and related structures

In the present work, mean dipole polarizabilities of the nanodiamonds and the related nanostructures modified with nitrogen vacancy centers or surface functional groups F and OH have been studied by DFT methods. Linear correlation between the mean polarizability and the size of nanodiamonds has been justified. It opens opportunities for prediction of polarizabilities of larger nanodiamond particles without high-cost quantum-chemical calculations. Introducing nitrogen vacancy centers slightly increases the resulting mean polarizability due to the repulsive interactions of lone pairs of N atoms (in A, B, and N3 centers) or unpaired electron (C center). Mean polarizabilities of polyfluorinated and polyhydroxylated nanodiamonds have been calculated for model structures with isolated, focal, and compact arrangements of the F/OHs on the surface. The enhancement of polarizability over the expected additive value has been found for nanodiamonds with compact placement of F/OH and in the case of the polyhydroxylated nanodiamond with the isolated OH groups.

Enhancement of polarizabilities of cylinders with cylinder-slab resonances.

If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much “brighter” is actually closely related to the reverse effect known in the literature as “cloaking by anomalous resonance” which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder.

Quantum Mechanical Study of Pre-Dissociation Enhancement of Linear and Nonlinear Polarizabilities of (TeO2)n Oligomers as a Key to Understanding the Remarkable Dielectric Properties of TeO2 Glasses

The effects of intermolecular interactions of TeO(2) molecules in the (TeO(2))(n) oligomers on the polarizability (α) and second hyperpolarizability (γ) are investigated by the use of a density functional method. A significant intermolecular distance dependence of both quantities is observed. The huge dissociation-induced polarizability enhancement is analyzed in terms of the molecular orbital evolution. It is shown that the obtained results can provide a new look at the microscopic origin of the extraordinary dielectric properties of TeO(2) glass.

Phase and Optical Characterizations of Annealed SnO Thin Films and Their p-Type TFT Application

Amorphous SnO thin films were prepared on quartz and 190 nm substrates by electron beam evaporation. X-ray diffraction results reveal that amorphous SnO transforms into polycrystalline (tetragonal litharge structure) after rapid thermal annealing in Ar ambient at and starts decomposing into (orthorhombic structure) with the expulsion of Sn atoms at . The optical properties were characterized via spectroscopic ellipsometry. The polycrystalline SnO thin films have a higher refractive index and a narrower bandgap than the amorphous ones, which is due to the polarizability enhancement in the crystallization process. Moreover, the relationship between and of the amorphous and polycrystalline SnO thin films can be explained by the “Moss rule” law, and a decreasing trend in was verified with the transformation from SnO to . Bottom-gate-type thin film transistors (TFTs) employing polycrystalline SnO channels on the substrates exhibit p-type field-effect transistor characteristics. The optimum field-effect mobilities and are 0.46 and , respectively, which are the same order of magnitude as those reported for epitaxial SnO TFTs.

Thermal stability of microstructural and optical modifications induced in sapphire by ultrafast laser filamentation

We report on the thermal stability of both structural and optical micromodifications created by ultrafast laser written filaments in sapphire crystals. By using the Cr3+ traces as optical probes, we have concluded that the filaments are constituted by both reversible and nonreversible defects with very different spatial locations. The strain field measured from the analysis of R lines has been found to be erased at the same time when the reversible centers are recombined (∼1100 °C). This fact seems to indicate that these defects act as pinning centers for the induced stress. Furthermore, we have found that the waveguide generated in the proximity of the filament disappear for annealing temperatures above 1100 °C. This clearly supports the assumption that waveguiding is produced by the strain stress induced refractive index increment based on the dominant electronic polarizability enhancement.

High repetition rate UV ultrafast laser inscription of buried channel waveguides in Sapphire: Fabrication and fluorescence imaging via ruby R lines

We report on the fabrication of buried cannel waveguides in Sapphire crystals by 250-kHz high repetition rate ultrafast laser inscription with 385 nm pulses. The propagation properties of the waveguides were studied as a function of the writing conditions. The micro-fluorescence analysis of the R lines generated by trace Cr(3+) dopant in Sapphire is used to elucidate the micro-structural modifications induced in the crystal network. It is revealed that waveguide has been formed due to local dilatation of the Sapphire network generated in the surroundings of the focal volume. The refractive index increment due to the dilatation induced electronic polarizability enhancement has been estimated to be of the order of Deltan approximately 10(-4).

Mechanism for effective polarizability enhancement in molecular crystals: C 60

Effective polarizabilities of molecules in the crystal environment are typically larger than those of molecules in the gas-phase, whereas most environmental effects make them smaller. It is shown that unbound charge-transfer configurations can produce the necessary enhancement. An average energy model and a background dielectric model applied to fullerene C 60 each produce enhancement consistent with that observed experimentally.

Quantum Size Effects in the Polarizability of Carbon Fullerenes

We investigate the size-dependent dielectric response of carbon fullerenes with up to 3840 atoms in the framework of the linear response theory. Our results suggest a significant polarizability enhancement due to quantum size effects with respect to classical or semiclassical calculations. The accuracy of our results, based on a parametrized Hamiltonian, is verified by ab initio time dependent density functional calculations for smaller fullerenes. Our findings underline the importance of quantum effects in the electronic response of nano- and mesoscopic systems.

Analysis of Semiconductor Cluster Beam Polarization Taking Small Permanent Dipole Moments into Account

Abstract Deflections of semiconductor cluster beams in an inhomogeneous electric field deliver enhanced polarizabilities for cold isolated Ga N As M clusters with odd number of atoms n=N+M up to n=17. One speculated that the high polarizabilities result from their electronic open shell structure. This was qualitatively confirmed by optical absorption cross section measurements, but the enhancement of polarizability is too large to be explained through a Kramers–Kronig-relation as purely electronic effect. Moreover, quantum chemical calculations gave permanent dipole moments of some tenths of a Debye for certain compositions. The clusters are too heavy to identify these dipole moments by beam broadening effects, but we will show in the present analytic investigation within classical top theory, that a slight reversible-adiabatic alignment of the clusters dipole moment in the electric field increases the average beam deflection and the derived polarizability values. This effect was up to now not taken into account and it offers a consistent explanation of the Ga N As M polarizabilities by small permanent dipole moments of some tenths of a Debye and a reasonable rotational temperature between 2 and 12K.

Excited-state polarizability of J-aggregates

The difference between the static polarizabilities of the first excited and the ground state of J-aggregates has been derived using the sum-over-states approach. For a simple model analytical expressions as well as numerical calculations show that the polarizability enhancement upon excitation should depend only marginally on the aggregate size. Charge-transfer states have been suggested as the possible origin of the observed large excited-state polarizabilities of J-aggregates.

Dielectric anomaly of porous media: The role of multipolar interactions.

We examine the role of multipolar couplings among brine-filled pores in the low-frequency dielectric anomaly of porous media. We show that the polarizability enhancement caused by these couplings can give rise to a large dielectric response. The effect requires that there be pores separated from each other by thin walls, and its strength is sensitively determined by the microgeometry of the sample.

Polarizability enhancement in doped semiconductors near the metal-insulator transition

The static polarizability at $T=0$ K of a doped semiconductor is evaluated in the single-bubble diagram approximation. The impurities are assumed to have a Gaussian distribution around an "averaged" regular array which is immersed in a dielectric continuum background. The effect of the randomness to the leading order in $\frac{\ensuremath{\sigma}}{d}$, $\frac{{a}_{0}}{d}$, where $d$ is the averaged lattice constant, $\ensuremath{\sigma}$ is the Gaussian width, and ${a}_{0}$ is the effective Bohr radius, is found to produce an ever increasing enhancement of the polarizability as the doping concentration is increased.

The low-frequency, low-temperature dielectric behavior of n-type germanium below the insulator-metal transition

Dielectric constant and ac conductance measurements of a number of n-type Ge samples (mostly Sb-doped) have been made with a low-frequency, three-terminal capacitance bridge between 4.2 and 0.011 K. From the concentration dependence of the low-temperature asymptotic values of the dielectric constant the value of the polarizability of the Sb donor has been determined to be αSb = (7.3 ± 1.0) × 106 »3. When employed with a new theory of the polarizability enhancement α D (N)/α D (0) and the Clausius-Mossotti expression, a calculated value of N c,calc = 2.5 × 1017/cm3 is obtained for the onset of metallic behavior for Ge:Sb. Although much larger than the current value of 1 × 1017/cm accepted in the literature, a correction of the neutral donor densities employing room-temperature resistivities and the Sze-Irvine curve rather than Hall coefficient data as applied to the transport data of Fritzsche shows N c,expt ≈ (1.9 ± 0.1) × 1017/cm. Data on ultra high-purity Ge samples yield a host dielectric constant ɛGe = 15.40−0.08 +0.01 (after a Kramers-Kronig analysis correction to remove a hopping conductivity contribution to ɛ), in excellent agreement with the value of 15.36 determined by Faulkner from the positions of the 2p and 3p levels of the Sb shallow donors. The data demonstrate the importance of the Kramers-Kronig analysis in obtaining values of ɛ(N) without any conductivity contribution. The ac conductance data are also briefly discussed.