Characterization of structural, electrical conductivity and dielectric properties of 1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1benzopyran-2,2'[2H] indole] compound

The structural properties of 1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro [2H-1-benzopyran-2,2'-[2H]indole] (DTNBI) characterized using X-ray diffraction. DTNBI's powder has a monoclinic polycrystalline structure. The DTNBI's lattice constant of unit cell are ( a = 29.912 Å, b = 18.815 Å, and c = 13.062 Å). The mean crystallite size and strain were evaluated using the formula of Scherrer, Williamson-Hall, and Size-Strain plots methods. In the frequency range of 40 to 5×106 Hz, the dependence of ac conductivity was studiedforthe bulk DTNBI upon different temperatures (303-363 K). The prevailing mechanism for the ac conduction was the correlated barrier hopping model for bulk DTNBI.The dielectric constant and the dielectric loss were also studied. The dielectric polarization mechanism of bulk DTNBI used to explain the behavior of the real, ε1, and imaginary, ε2, components of the complex dielectric constant. Reliance of dc and ac conductivity of bulk DTNBI follows the law of Arrhenius. The activation energy of both dc and ac conduction for bulk DTNBI were calculated and the dielectric characteristics were examined via complex electric modulus formalism

Fourier-transform infrared and electrical properties of magnesium phthalocyanine thin films

The Fourier-transform infrared (FT-IR) spectra of magnesium phthalocyanine (MgPc) were investigated in the spectral range 500–4000 cm-1. The spectra allow characterization of vibration modes. A comparison of absorption spectra of powder, as-deposited and annealed films is presented. The dark electrical resistivity measurements were carried out at different temperatures in the range 308 to 423 K. Two activation energies ΔE1 = 0.23 eV and ΔE2 = 0.69 eV were obtained. The thermal activation energy ΔE1 is associated with impurity conduction and ΔE2 is associated with intrinsic conduction. The current density-voltage characteristics of MgPc at room temperature showed a linear ohmic conduction mechanism at low voltages. At higher voltages the space-charge-limited conduction (SCLC) accompanied as a single dominant level. The temperature dependence of current density allows the determination of some essential parameters such as the hole mobility (μh), the trapping factor Θ and the total trap concentration (Nt)

Study of dielectric relaxation and AC conductivity of InP:S single crystal

The dielectric relaxation and AC conductivity of InP:S single crystal were studied in the frequency range from 100 to 5.25 × 105 Hz and in the temperature range from 296 to 455 K. The dependence of the dielectric constant (ε1) and the dielectric loss (ε2) on both frequency and temperature was investigated. Since no peak was observed on the dielectric loss, we used a method based on the electric modulus to evaluate the activation energy of the dielectric relaxation. Scaling of the electric modulus spectra showed that the charge transport dynamics is independent of temperature. The AC conductivity (σAC) was found to obey the power law: Aωs. Analysis of the AC conductivity data and the frequency exponent showed that the correlated barrier hopping (CBH) model is the dominant mechanism for the AC conduction. The variation of AC conductivity with temperature at different frequencies showed that σAC is a thermally activated process

Transport mechanisms and photovoltaic properties of zinc tetraphenylporphyrin/

The DC electrical measurements on Au/ZnTPP/Au planar structure showed two regimes of electrical conductivity depending on temperature, at low temperatures the activation energy is 0.24 eV and variable range hopping in localized states near Fermi level is the operating conduction mechanism, at high temperatures the activation energy is 0.998 eV and phonon-assisted hopping of small polarons is the operating conduction mechanism. The capacitance-voltage measurements on Au/ZnTPP/n-Si/Al showed that the formed junction is linearly graded one. The thickness of depletion region in ZnTPP and n-Si has been determined and the built-in potential is 0.85 V. The concentration gradient of holes and electrons is 2.6 × 1020 holes/m4 and 0.3 × 1020 electrons/m4, respectively. Thermoelectric power measurements showed that ZnTPP films are p-type semiconductor and polaron activation energy is 0.37 eV. A hybrid solar cell of Au/ZnTPP/n-Si/Al had been constructed by growing ZnTPP film via thermal evaporation technique on n-Si wafer. Dark current-voltage measurements of the device at different temperatures showed that there are three conduction mechanisms operating in the device. The dominance of any of them depends on applied potential. The photovoltaic properties of Au/ZnTPP/n-Si/Al hybrid solar had been evaluated

Preparation and characterization of Au/n-GaSe

GaSe4 films were prepared using thermal evaporation technique onto glass and Si substrates. GaSe4 in both ingot and thin films was studied by hot probe procedure indicated n-type semiconductor. The conductivity activation energy (ΔE) decreased from 0.414 to 0.365 eV with the increase in film thickness from 90 to 500 nm. Investigation of the heterojunction n-GaSe4/p-Si by using characteristics indicated good rectification with rectification ratio of 48 at room temperature and at V = ±1.6 V. The ideality factor decreased from 2.2 to 2.13 while the reverse saturation current decreased from 8.3 × 10−7 A to 3.27 × 10−7 A by the temperature rise from 310 to 363 K. For lower and higher values of applied voltage, Pool-Frenkel and Schottky coefficients were 2.2 × 10−5 and 0.7 × 10−5 eV m−1/2, beside that, Schottky barrier height was found to be 0.4 eV. The thermionic emission mechanism occurs in the low forward voltage range but in the high forward region, the space-charge-limited current (SCLC) controlled by a single trap level is the dominant mechanism. In the reverse direction the Poole-Frenkel mechanism is the operating mechanism. Analysis of C-V characteristics of Au/n-GaSe4/p-Si/Al heterojunction gives the values of effective density of states (N) of 2.4 × 1034 cm−3 and the built-in voltage (Vb) of the junction is 0.78 V

Structural and optical characterizations of Ni (II) tetraphenyl porphyrin thin films

Thermal evaporation technique was used to prepare thin films of 5,10,15,20-tetraphenyl-21H,23H-porphine nickel (II), NiTPP, onto glass and quartz substrates. The crystal structures and morphologies of all prepared NiTTP thin films were investigated at 298, 423 and 573 K by using X-ray diffraction, XRD, and scan electron microscopy, SEM, respectively. The lattice of all prepared NiTPP films was investigated as a monoclinic with space group P2/M. The surface topography of the prepared films showed granular particles of sizes 49.7, 64.7 and 107 nm. The annealed NiTPP films at 423 K have a spatial configuration of well-defined grains boundary with nanoporous nature and all annealed films at 573 K have higher aggregates and the porosity of the films was increased. Optical constants namely refractive index, n, and the absorption index, k, of NiTPP films have been estimated by using spectrophotometric measurements of transmittance and reflectance in the spectral range from 200 to 2500 nm. The absorption spectra in the UV-vis spectrum were analyzed in terms of both molecular orbital and band theories. The obtained data of n and k were used to estimate the type of transitions and were found to be indirect transition for all films. The optical and fundamental gaps were decreased as the annealing temperature was increased. Some optical parameters namely molar extinction coefficient, εmolar, oscillator strength, f, and electric dipole strength, q2, have been evaluated. According to the single oscillator model and Drude model, some related parameters such as oscillation energy, Eo, the dispersion energy, Ed, the optical dielectric constant, ε∞, the lattice dielectric constant, εL, and the ratio of free carrier concentration to its effective mass, N/m∗, the third-order nonlinear susceptibility, χ(3), and molar polarizability, αp, were estimated before and after annealing

Structural and optical properties of thermally evaporated cadmium thiogallate CdGa

Nano structure films of cadmium thiogallate CdGa2S4 have been prepared by a conventional thermal evaporation technique (at substrate temperature = 303 K). These films were deposited on both glass and quartz substrates. X-ray diffraction measurements showed that CdGa2S4 compound in the powder form has a polycrystalline nature with a tetragonal structure. The as-deposited film was annealed at 673 K for 2 h under vacuum 10-3 Pa and was irradiated by 10 kGy γco rays. This resulted in a transformation to nanostructure grains of CdGa2S4 thin films. Transmission electron microscopy was carried out for all of the investigated films, which also confirmed that those films could be transformed to nanostructure grains. Optical properties of the CdGa2S4 films under investigation were examined using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range 400–2500 nm. It was found that both refractive index n and absorption index k changed with the heat and irradiation treatments. The dispersion of refractive index in CdGa2S4 was analyzed according to the single oscillator model. Some dispersion parameters were determined for all investigated films. The calculated values of β (which is defined as the parameter used to determine the type of crystal) indicate that CdGa2S4 belongs to the covalent class for all films investigated. The ratio of the free carrier concentration to the effective mass N/m* was also determined. The analysis of the absorption coefficient indicated that this ternary defect chalcopyrite compound has both direct and indirect transitions in relevance to the energy gaps Eg1dir, Eg2dir and Egind, respectively. These energy values decreased by irradiation, while they increased by annealing