Frequency- and voltage-dependent dielectric properties and electrical conductivity of Au/PVA (Bi-doped)/n-Si Schottky barrier diodes at room temperature

In this study, frequency and voltage dependence of dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), the real and imaginary parts of electric modulus (M′ and M″) and ac electrical conductivity (σ _ac) of an Au/PVA (Bi-doped)/n-Si Schottky barrier diode have been investigated in detail by using experimental C–V and G–V measurements in the wide frequency range of 5 kHz–10 MHz and the voltage range of ±2 V at room temperature. Experimental results indicate that the values of ε′,ε″, tanδ and σ _ac are strongly frequency and voltage dependent. It has found that the values of ε′,ε″ and tanδ decrease while the values of σ _ac, M′ and M″ increase. It is clear that the values of M″ show a distinctive peak with a U-shape and its position shifts towards the positive-bias region with increasing frequency. Such behavior of the peak can be attributed to the particular distribution of interface states located at the Si/PVA interface and interfacial polarization. It can be concluded that the interfacial polarization and the charge at the interface can easily follow the ac signal at low frequencies.     

A.c. conductivity and relaxation in LiCoVO4 ceramics

The LiCoVO₄ compound is synthesized by solution-based chemical method. X-ray diffraction analysis exhibits a single phase nature of the compound with cubic structure. The dielectric constant (ε_r), tangent loss (tanδ) and a.c. conductivity (σ_ac) have been studied as a function of frequency and temperature using complex impedance spectroscopy (CIS) technique. The variation of (ε_r and tanδ) with frequency at studied temperatures shows a dispersive behavior at low frequencies. Frequency dependence of σ_ac at different temperatures obeys Jonscher’s universal power law governed by the relation: σ_ac = σ_dc + Aωⁿ, where n is the frequency exponent in the range of 0 ⩽ n ⩽ 1 and A is a constant that depends upon temperature.     

Fine and hyperfine structure in 14N2+

The fine and hyperfine structure of ¹⁴N₂⁺ has been observed in 31 rotational lines of the (0, 1) band of the B²Σ_u⁺-X²Σ_g⁺ system using the method of Doppler-tuned laser-induced fluorescence on a molecular ion beam. The spin-rotation constants (γ′, γ″, γ′_J) are in good agreement with other experiments in which the hyperfine structure was not resolved. The Fermi-contact (b′_F, b″_F) and dipolar (t′, t″) hyperfine coupling constants are in reasonably good agreement with values calculated from ab initio wavefunctions. The least-squares experimental values in MHz are γ″ = 279.1(6), γ′ = 726.4(6), γ′_J = ?0.0460(2), b″_F = 105(4), b′_F = 708(3), t″ = 49(6), and t′ = 26(5).     

The effect of gamma irradiation on electrical and dielectric properties of Al-TiW-Pd2Si/n-Si Schottky diode at room temperature

The effects of ⁶⁰Co (γ-ray) irradiation on the electrical and dielectric properties of Al-TiW-Pd₂Si/n-Si Schottky diodes (SDs) have been investigated by using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at room temperature and 500 KHz. The corrected capacitance and conductance values were obtained by eliminating the effect of series resistance (R_s) on the measured capacitance (C_m) and conductance (G_m) values. The high-low frequency capacitance (CHF-CLF) method given in [12] as N_ss = (1/qA) [((1/C_LF) − (1/C_ox))⁻¹ −  ((1/C_HF) − (1/C_ox))⁻¹] was successfully adapted to the before-after irradiation capacitance given in this report as N_ss = (1/qA) [((1/C_bef) − (1/C_ox))⁻¹ − ((1/C_after) − (1/C_ox))⁻¹] for the analyzing the density of interface states. The N_ss-V plots give a distinct peak corresponding to localized interface states regions at metal and semiconductor interface. The experimental values of the ac electrical conductivity (σ_ac), the real (M′) and imaginary (M″) parts of the electrical modulus were found to be strong functions of radiation and applied bias voltage, especially in the depletion and accumulation regions. The changes in the dielectric properties in the depletion and accumulation regions stem especially from the restructuring and reordering of the charges at interface states and surface polarization whereas those in the accumulation region are caused by series resistance effect.     

Effect of Pb on the electrical properties of a-Ge20Se80 glasses

The present paper reports the effect of Pb impurity (low ∼2 at% and high ∼10 at%) on the ac conductivity (σ_ac) of a-Ge₂₀Se₈₀ glass. Frequency-dependent ac conductance and capacitance of the samples over a frequency range ∼100 Hz to 50 kHz have been taken in the temperature range ∼268 to 358 K. At frequency 2 kHz and temperature 298 K, the value of σ_ac increases at low as well as at higher concentration of Pb. σ_ac is proportional to ω^s for undoped and doped samples. The value of frequency exponent (s) decreases as the temperature increases. The static permittivity (ε_s) increases at both Pb concentrations. These results have been explained on the basis of some structural changes at low and higher concentration of Pb impurity.     

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293–333 K) and frequency range (50–5×10⁶ Hz). The frequency dependence of ac conductivity, σ_ac, has been investigated by the universal power law, σ_ac(ω)=Aω^s. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σ_ac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.     

Rotational analysis of the B2Σ+ → X2Σ+ system of the aluminum monoxide radical,AlO

Twenty-five bands of the B²Σ → X²Σ system of AlO with 0 ≤ v′ ≤ 9 and 0 ≤ v″ ≤ 6 have been photographed at high resolution. The measured positions of the assigned lines of each band have been fitted by least-squares to obtain estimates of the constants (B′, D′, B″, D″), the band origin, and Δγ_v′,v″, which is the difference of the upper and lower state spin-doubling constants (γ′_v and γ″_v). The parameters from individual bands have been merged to single-valued estimates, as well as to polynomial representations in ($\text{v +}\text{1}\text{2}$). Although the spin-doubling constants are not found absolutely for either state, their vibrational dependences are well determined. The data are employed in the computation of RKR potential energy curves and an array of Franck-Condon factors and r-centroids.     

Dielectric properties of BiMg1/2Ti1/2O3 and BiMg1/2Zr1/2O3 perovskite ceramics with elimination of the contribution for direct current conductivity

A technique for analysis of the electric modulus spectrum of dielectric ceramics based on the elimination of the direct current conductivity (σ _dc ) contribution has been developed. Expressions are given for the real (M′ _ac ) and imaginary (M′′ _ac ) parts of the complex electrical modulus related only to the dielectric polarization and not containing the contribution of σ _dc . The frequency dependence of M′′ _ac and the M′′ _ac – M′ _ac diagram for BiMg_1/2Ti_1/2O₃ and BiMg_1/2Zr_1/2O₃ perovskite ceramics are analyzed.     

Influence of lithium potassium zirconate nanoparticles on the electrical properties and structural characteristics of poly(vinyl alcohol) films

We investigated the influence of lithium potassium zirconate (LiKZrO₃) nanoparticles on the electrical properties and structural characteristics of poly(vinyl alcohol) (PVA) films. PVA/LiKZrO₃ nanocomposite films were prepared by casting of aqueous solutions with varying LiKZrO₃ content (0.5, 1.0, and 2.0 wt.%). The dielectric constant (ε′), dielectric loss (ε″), AC conductivity (σ_ac), dielectric loss tangent (tan δ), and electric modulus (M′ and M″) of the nanocomposite films were measured over a range of frequencies at ambient temperature. The results show increases in σ_ac and M′ with frequency, whereas ε′, ε″, and tan δ decreased with increasing frequency. The films were also characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) techniques. DSC and XRD revealed the nature of LiKZrO₃ nanoparticle interaction with the PVA matrix. TGA analysis revealed an increase in thermal stability of the nanocomposites with increasing nanoparticle concentration. Scanning electron microscopy confirmed uniform dispersion of LiKZrO₃ nanoparticles in the PVA matrix.     

Electronic spectra and structure of the hydrogen halides: Characterization of the electronic structures of HBr and DBr lying between 79 500 and 83 900 cm−1 above X1Σ+

The high-resolution absorption spectra of HBr and DBr were reinvestigated in the 1258-Å (79 500 cm^?1) to 1192-Å (83 900 cm^?1) region. This spectral region was found to contain bands attributable to (1) V¹Σ⁺-X¹Σ⁺(v′ - 0) with v′ > 0, (2) (v′ - 0) transitions with v′ > 0 from X¹Σ⁺(v″ = 0) to states associated with the (σ²π³)cπ and (σ²π³)cσ configurations, and (3) (v′ - 0) transitions with $\text{v′ ≧ 0}$ from X¹Σ⁺(v″ = 0) to states associated with the previously unreported configurations (σ²π³)dσ, dπ, aδ, eσ, and fσ.     

Effect of magnesium substitution on dielectric and magnetic properties of Ni-Zn ferrite

The dielectric and magnetic properties of Mg incorporated Ni-Zn spinel ferrites have been investigated. Ni_0.5−xZn_0.5Mg_xFe₂O₄ ferrites have been prepared by sol-gel auto-combustion technique. The as prepared ferrites were annealed at 673, 873 and 1073 K. The X-ray diffraction studies reveal the spinel structure of annealed ferrites. The TEM results are in agreement with XRD results. FTIR study has also been carried out to get insight into the structure of these ferrites. The dielectric measurements show that the dielectric constant (ε′), dielectric loss (tan δ) and conductivity (σ_ac) increase on incorporation of Mg in the Ni-Zn ferrite. ε′, tan δ and σ_ac also show dependence on temperature, frequency of external applied electric field and microstructure of the samples. The magnetic moment measurements reveal that the saturation magnetization (M_s) increases and coercivity (H_c) decreases with the increase in concentration of Mg²⁺ ions. M_s and H_c also show dependence on the annealing temperature.     

Laser-induced fluorescence and microwave-optical double-resonance study of the B1Σ+-X1Σ+ system of magnesium monoxide

Doppler-limited, laser-induced fluorescence spectra on the B¹Σ⁺-X¹Σ⁺ (v′ = v″ = 0 and 1) system of MgO have been obtained. The results of the optical analysis were merged with our microwave-optical double-resonance measurements to produce the following set of spectroscopic parameters for the B and X states, where the units are in cm^?1, and the uncertainties represent 95% confidence limits: T′_0.0 = 20003.594(2); B′₀ = 0.58004(3); D′₀ = 1.13(2) × 10^?6; B″₀ = 0.57198(3); D″₀ = 1.20(2) × 10⁶; T′_1.1 = 20043.423(2); B′₁ = 0.57528(4); D′₁ = 1.14(11) × 10⁶; B″₁ = 0.56674(4); D″₁ = 1.22(10) × 10⁶.     

Spectroscopic investigations and electrical properties of PVA/PVP blend filled with different concentrations of nickel chloride

Films of PVA/PVP blend (50/50) filled with different concentrations of NiCl₂ were prepared by casting method. The prepared films were investigated by different techniques. XRD scans demonstrated that the peak intensity at 2θ≈20° decreased and the band width increased with increase in the concentrations of NiCl₂ content, which implied decrease in the degree of crystallization and hence causes increase in the amorphous region. UV-vis analysis revealed that the values of the optical band gap are affected with increase in NiCl₂ content. This indicates the formation of charge transfer complexes between the polymer blend and the filler. The rise of conductivity is significant with increased concentration of NiCl₂ filler; this reveals an increase in degree of amorphosity. AC conductivity (σ_ac) behavior of all the prepared films was investigated over the frequency range 42 Hz-5 MHz and under different isothermal stabilization in the temperature range 313-393 K. It suggests that the hopping mechanism might be playing an important role in the conduction process in high frequency region. The dielectric behavior was analyzed using dielectric permittivity (ε´, ε″) dielectric loss tangent (tan δ) and electric modulus (M″). The decrease in dielectric permittivity was observed with increase in the concentration of NiCl₂ filler. This suggests the role of NiCl₂ as filler to improve the electrical conductivity of PVA/PVP blend.     

AC conductivity and dielectric properties of bulk tungsten trioxide (WO3)

AC conductivity and dielectric properties of tungsten trioxide (WO₃) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, σ_ac(ω) was found to be a function of ω^s where ω is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO₃. The dielectric constant (ε′) and dielectric loss (ε″) were measured. The Cole–Cole diagram determined complex impedance for different temperatures.     

Study of (Bi2O3)(BaxMo1−xO3) polycrystalline ceramic as relaxor ferroelectric

Solid solutions of bismuth layered (Bi₂O₃)(Ba_xMo_1−xO₃) (0.2≤x≤0.8, x is in step of 0.2) ceramics were prepared by conventional solid-state reaction of the constitutive oxides at optimized temperatures with a view to study its electrical properties. Powder X-ray diffraction has been employed for physical characterization and an average grain size of ∼16 to 22 nm was obtained. XRD study reveals the single phase structure of the samples. Dielectric properties such as dielectric constant (ε′), dielectric loss (tanδ) and ac electrical conductivity (σ_ac) of the prepared ceramics sintered at various temperatures in the frequency range 10¹–10⁷ Hz have been studied. A strong dispersion observed in the dielectric properties shows the relaxor type behavior of the ceramic. The presence of maxima in the dielectric permittivity spectra indicates the ferroelectric behavior of the samples. Impedance plots (Cole–Cole plots) at different frequencies and temperatures were used to analyze the electric behavior. The value of grain resistance increases with the increase in Ba ion concentration. The conductivity mechanism shows a frequency dependence, which can be ascribed to the space charge mainly due to the oxygen vacancies. The relaxation observed for the M″ (ω) or Z″ (ω) curves is correlated to both localized and long range conduction. A single ‘master curve’ for the normalized plots of all the modulus isotherms observed for a given composition indicates that the conductivity relaxation is temperature independent.     

Impact of MoO3 concentration,frequency and temperature on the dielectric properties of zinc phosphate glasses

Phosphate glasses with the chemical composition of 47P₂O₅–24ZnO-(29-x)Na₂O-xMoO₃, x = 0, 2, 4, 6, 8 and 10, have been prepared using the melt quenching technique. Dielectric properties of these phosphate glasses are carried out in the frequency range from 1 to 100 kHz at different temperatures. Dielectric parameters such as dielectric constant ε′, dielectric loss ε′′ and ac conductivity of the investigated glasses have been evaluated. The dependences of these dielectric parameters on frequency, composition and temperature have been discussed. It is found that dielectric constant decreases with increasing frequency due to the reduction of space-charge polarization and dipole polarization. The dependence of ac conductivity on the MoO₃ content indicates a competition between electronic and ionic conduction. The temperature dependence of the dielectric parameters reveals a rising trend of the dielectric parameters with temperature. This rising trend is indicated due to the increase of the amplitude of the thermal vibration of the charge carriers which facilitates the electron hopping and drifting of the mobile ions. The linear trend of the ln(σ_ac)-1000/T plot indicates that ac conductivity of the investigated glasses is thermally-activated transport process and follows the Arrhenius equation. The activation energy and its composition dependence have been reported.     

Thermal,dielectric and conductivity studies on PVA/Ionic liquid [EMIM][EtSO4] based polymer electrolytes

Polymer electrolyte films of (PVA+15 wt% LiClO₄)+x wt% Ionic liquid (IL) 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO₄] (x=0, 5, 10, 15) were prepared by solution cast technique. These films were characterized using TGA, DSC, XRD and ac impedance spectroscopic techniques. XRD result shows that amorphosity increases as the amount of the IL in PVA+salt (LiClO₄) is increased. DSC results confirm the same (except (PVA+15 wt% LiClO₄)+10 wt% IL). The dielectric and conductivity measurements were carried out on these films as a function of frequency and temperature. The addition of IL significantly improved the ionic conductivity of polymer electrolytes. Relaxation frequency vs. temperature plot for (PVA+15 wt% LiClO₄)+x wt% IL were found to follow an Arrhenius nature. The dielectric behavior was analyzed using real and imaginary parts of dielectric constant, dielectric loss tangent (tan δ) and electric modulus (M′ and M″).     

Pulsed excimer laser ablation growth and characterization of Ba(Sn0.1Ti0.9)O3 thin films

Polycrystalline thin films of Ba(Sn_0.1Ti_0.9)O₃ were deposited on Pt coated silicon substrates by pulsed excimer laser ablation technique. The room temperature dielectric constant of the Ba(Sn_0.1Ti_0.9)O₃ films was 350 at a frequency of 100 kHz. The films showed a slightly diffused phase transition in the range of 275–340 K. The polarization hysteresis behavior confirmed the ferroelectric nature of the thin films. Remanent polarization (P_r) and saturation polarization (P_s) were 1.1 and 3.2 μC/cm², respectively. The asymmetric capacitance–voltage curve for Ba(Sn_0.1Ti_0.9)O₃ was attributed to the difference in the nature of the electrodes. Dispersion in both the real (ε′_r) and imaginary (ε″_r) parts of the dielectric constant at low frequencies with increase in temperature was attributed to space charge contribution in the complex dielectric constant.     

Perturbation determinants for singular perturbations

Let A be a densely defined symmetric operator and let {Ã′, Ã} be an ordered pair of proper extensions of A such that their resolvent difference is of trace class. We study the perturbation determinant Δ_Ã′/Ã(·) of the singular pair {Ã′, Ã} by using the boundary triplet approach. We show that, under additional mild assumptions on {Ã′, Ã, the perturbation determinant Δ_Ã′/Ã(·) is the ratio of two ordinary determinants involving the Weyl function and boundary operators. In particular, if the deficiency indices of A are finite, then we obtain Δ_Ã′/Ã(z) = det (B′ - M(z))/det (B - M (z)), z ∈ ρ(Ã), where M(·) stands for the Weyl function and B′ and B for the boundary operators corresponding to Ã′ and à with respect to a chosen boundary triplet Π. The results are applied to ordinary differential operators and to second-order elliptic operators.     

The B(2Σ+) → X(2Σ+) transition (4050–4500 Å) in Hgl

The B → X band system (4050–4500 Å) of HgI is photographed and vibrationally analyzed for the isotopically pure species ²⁰⁰Hg¹²⁷I and ²⁰⁰Hg¹²⁹I. The assigned bands span v″ levels 5–26 and v′ levels 0–13. The least-squares analysis indicates that the previously accepted v″ numbering for this system is one unit too high. Band-profile simulations and Franck-Condon calculations indicate that the internuclear separation (R′_e-R″_e) is 0.49 Å. The ground-state dissociation energy ($\text{D}$_e) is estimated to be 2750 ± 80 cm^?1. Spin splitting is found to contribute significantly to the band structure.