Ranoo Bhargav; Asit Patra; Suresh Chand
Abstract
Here, we investigate the hole transport mechanism in poly(3-hexylthiophene) (P3HT). First, ohmic contact has been established at indium tin oxide (ITO)/P3HT interface by molybdenum oxide (MoOx) hole injection layer. Thickness of MoOx layer is observed to play a crucial role with ohmic contact being observed ...
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Here, we investigate the hole transport mechanism in poly(3-hexylthiophene) (P3HT). First, ohmic contact has been established at indium tin oxide (ITO)/P3HT interface by molybdenum oxide (MoOx) hole injection layer. Thickness of MoOx layer is observed to play a crucial role with ohmic contact being observed even for 1 nm layer. However, device with less than 5 nm layer are found to be extremely unstable. A device with a 5 nm layer of MoOx is found to be stable and ohmic injection at ITO/P3HT layer enabled to observe ohmic conduction at low voltages (< 3 V), trap free space charge limited conduction (SCLC) for > 3 V. At higher voltages, effect of field on charge carrier mobility is also observed. Observation of SCLC enabled us to directly evaluate the hole mobility in P3HT which is calculated to be 5.4 × 10 -5 cm 2 /Vs. Conductivity is calculated from the low voltage region and found to be 6.85 × 10 -8 S/cm. Temperature dependent mobility is used to study the charge transport behavior and it has been observed that mobility is thermally activated with an extremely low activation energy of 39 meV.
Nimesh P. Patel; M. Srinivas; Vishwnath Verma; Dhaval Modi; K. V. R.Murthy
Abstract
Thermoluminescence (TL) of Sr2P < sub>2O7: Er 3+ phosphors had been studied in order to investigate the nature of the trapping centers created due to doping ions. The effect of beta – irradiation was analyzed for various doses given to the samples. The measurements of TL glow curves have been done ...
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Thermoluminescence (TL) of Sr2P < sub>2O7: Er 3+ phosphors had been studied in order to investigate the nature of the trapping centers created due to doping ions. The effect of beta – irradiation was analyzed for various doses given to the samples. The measurements of TL glow curves have been done at the heating rate 6 K/s. The TL measurements done for the study of the dosimetric properties of samples showed that the β-dose response is linear from 5 Gy to about 50 Gy. The experimental glow curves had been analyzed by glow curve fitting technique which revealed that the glow curve is consist of three curves with peak temperature 400 K, 430 K and 464 K. The activation energy ‘Ea’ of the peaks had been calculated to be 0.90 ± 0.03 eV, 1.10 ± 0.04 eV and 1.05 ± 0.03 eV, respectively. The geometrical factor ‘μg’ having values 0.51, 0.52 and 0.48, imply that the glow curve having second order kinetics. The linear dose response, fading effect after exposed and reusability of samples are very reliable for dosimetry applications.
Sajad Ahmad Mir; M. Ikram; K. Sultan; Z. Habib; H. Kausar; K. Asokan
Abstract
Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain ...
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Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain size (0.2 μm to 0.3 μm) with an increase in Ni doping. The influences of Ni doping on optical energy band gap are investigated in the wavelength range of 200-800 nm. Dielectric properties (dielectric constant and loss) for SmFe1-xNixO3 were studied in the temperature range 100-400K and in the frequency range 20 kHz-1MHz. AC conductivity of pristine sample is found to be less than Ni doped samples. Various possibilities were explored to explain the observed dielectric and electric behavior of Ni doped SmFeO3 ceramics.
Khalid Sultan; M. Ikram
Abstract
Results from a detailed investigation on the structural, optical, electrical and magnetic properties of polycrystalline bulk samples of La1-xCaxMnO3 (x=0, 0.3, 0.5 and 0.7) synthesized by solid state reaction method are presented. The Rietveld analysis of the X-Ray diffraction (XRD) profiles clearly ...
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Results from a detailed investigation on the structural, optical, electrical and magnetic properties of polycrystalline bulk samples of La1-xCaxMnO3 (x=0, 0.3, 0.5 and 0.7) synthesized by solid state reaction method are presented. The Rietveld analysis of the X-Ray diffraction (XRD) profiles clearly indicated that the XRD patterns are well fitted with orthorhombic structure. Raman spectral features revealed their finger print modes and irreducible representations at the brillouin zone center as per the group theory. It is also observed that as doping is increased, these compounds tend towards a cubic form. Ooptical band gap ‘Eg’ study reveals that the Eg decreases with Ca doping resulting in increase in conductivity. This is consistent with the resistivity measurements. In all the samples, except when x = 0.0 and 0.7, the resistivity at the highest temperature measured (ρ300 K) is less than that at 5 K (ρ5K), although for temperature T<Tp, the material shows a metal variation of ρ with temperature (d ρ/dT > 0) whereas the value of ρ300 K decreases as x increases. Magnetization study revealed that temperatures corresponding to magnetic transitions Tc increases with doping. It is observed that the composition x = 0.5 show both a paramagnetic to ferromagnetic transition and an antiferromagnetic transition. An effort has been made to relate above observed results in the compound with the structural changes brought about by Ca doping.Possible mechanisms such as activated transport and Zener double exchange are used to understand the phase diagram of these materials.
Faruq Mohammad; Tanvir Arfin
Abstract
In continuation to our previous work, the superparamagnetic Fe3O4@Au core-shell type nanoparticles (NPs) were further characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), electrical conductivity, impedance and cyclic voltammetry measurements. From the analysis of ...
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In continuation to our previous work, the superparamagnetic Fe3O4@Au core-shell type nanoparticles (NPs) were further characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), electrical conductivity, impedance and cyclic voltammetry measurements. From the analysis of DSC and TGA results with our Fe3O4@Au NPs of about 6.25 ± 0.6 nm size, we observed a clear endothermic peak at 310°C due to the decomposition of the oleic acid/oleylamine surface ligands and the particles found to contain more than 80% of the metallic content from the mixed compositions of gold and iron oxide were observed. Because of the conduction through the Fe3O4@Au grain, the impedance profile of the pellet exhibited a well-resolved semi-circle and an inclined spike in a far low-frequency region. The electrical conductivity of the Fe3O4@Au material found to be increased with an increase of temperature. The standard Gibbs free energy (ΔG) of the reaction provided a criterion for spontaneous changes in the equilibrium of the material. From the analysis of the results of ΔG, it appears that at 25°C temperature, ΔS found to be negative. The calculated enthalpy, ΔH = -0.635 kJ/mol, at the corresponding entropy of ΔS = -0.132 kJ/mol. Finally, the activation energy in temperature range of 25-200°C for the Fe3O4@Au core-shell material was calculated using Line fitting and the surface characterization by using cyclic voltammetry. The electrochemical redox property of the Fe3O4@Au shows quasi-reversible wave corresponding to Au 3+ /Au 2+ .In addition, the electrochemical parameters for Fe3O4@Au NPs of E c p < /sub>, E a p < /sub>, E o 1/2 and were also obtained. Since the Fe3O4@Au material has low activation energy at low temperature range which makes it a good candidate as an ion conductor and even has the potential uses in many solid state devices and also in the future prospects of electrochemistry applications.
