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Correlation between the morphology and the opto-electronic and electrical properties of organometallic halide perovskite (CH<sub>3</sub>NH<sub>3</sub>MH<sub>3</sub>) thin films
摘要： Organometallic halide perovskites are emerging as a promising class of materials for optoelectronic applications. Crystal morphology is important for improving the organic-inorganic lead halide perovskite semiconductor property in optoelectronic, electrical and photovoltaic devices. It is thus important to investigate how the changes in crystal morphology affect the semiconductor behavior. This work presents a study that was carried out to assess the relationship between different deposition methodologies and the opto-electronic and electrical properties of the resultant organometallic halide perovskite thin films. Herein, single step solution deposition method and two step solution deposition methods have been used to deposit perovskite thin films. The structure and morphology of perovskite was controlled by changing concentration, annealing temperatures and dip coating times. From the study, prepared films showed different morphologies as the concentration, annealing temperatures and dip coating times were varied. Optical band gap energies of 2.23 eV, 2.13 eV and 2.09 eV were obtained for samples prepared by single step solution deposition method and 1.57 eV, 1.55 eV and 1.52 eV for two step solution deposition method. The sheet resistance values decreased with an increase in concentration, annealing temperatures and dip coating times. The decrease in optical band gap energy and sheet resistances are excellent properties for high performance photovoltaic devices.
关键词： Perovskite,sheet resistivity,activation energy,band gap,sheet resistance,spectroscopy
更新于2025-11-19 16:56:35
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Temperature-dependent dielectric response of (1-x)PVDF/(x)BaTiO3 nanocomposite films
摘要： The PVDF/BaTiO3 nanocomposite films were prepared by solution casting method by using dimethylformamide as solvent. The dielectric constant and loss tangent of the PVDF and PVDF/BaTiO3 composites have been determined as functions of frequency (20 Hz to 2 MHz) and temperature (80 to 425 K). A significant enhancement in dielectric constant ε' is observed in composite samples. Tangent loss factor (tan δ) is maximum at lower frequencies due to interfacial polarization. In composite samples owing to the synthesis process, there is a phase transition in PVDF from α to β which results in the formation of dipolar relaxation. The dipolar nature of both the PVDF and PVDF/BaTiO3 nanocomposites is arrested below 200 K. The activation energy values (0.43- 0.69 eV) associated with tan δ peak in the region 200 – 270 K are in agreement with the activation energy associated with a dipolar relaxation process. The relaxation time (τ) decreases with increasing BaTiO3 filler content while the number density of dipoles increases from 4.06×1021 cm-3 for pristine PVDF to 6.62×1023 cm-3 for (0.5)PVDF/(0.5)BaTiO3 composite and confirms a significant amount of dipolar relaxation in PVDF/BaTiO3 composites.
关键词： dielectric relaxation,activation energy,dielectric constant,PVDF/BaTiO3 nanocomposites
更新于2025-11-14 17:28:48
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Concentration effects on the thermally-activated transport of polarons in conducting polymers
摘要： The impact of the polaron concentration on the temperature-mediated charge transport in one-dimensional organic materials is studied. Within the scope of a tight-binding description, our findings reveal that high-temperature diffusivity tends to increase as polaron concentration increases. Moreover, the activation energy for the polaron transport also increases with polaron concentration. Importantly, the polaron diffusivity follows an Arrhenius-like behavior with low activation energy.
关键词： Activation energy,Organic materials,Polaron concentration,Diffusivity
更新于2025-09-23 15:23:52
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Thermoluminescent behavior of UV and γ rays irradiated Eu2+ and Er3+doped silicate phosphors
摘要： This paper reports the structural, morphological and thermoluminescent studies of Eu2+ and Er3+ ions activated ASiO3 (A= Ca, Ba, Sr) phosphors synthesized via conventional solid state reaction method. The impurity ions concentration of both Eu2+ and Er3+ ions varies from 0 mol% to 1 mol%. The study of crystallographic traits of the synthesized phosphors is done by Powder X-Ray Diffraction (PXRD) analysis. The crystalline nature, phase purity and appreciable homogeneity of the synthesized phosphors were confirmed by this study. The distinct morphological and topographical features were studied through Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). The thermoluminescent (TL) behavior of ultraviolet (UV) irradiated and gamma irradiated ASiO3:Eu2+, Er3+ (A= Ca, Ba, Sr) phosphors were studied here and the various kinetic parameters were estimated by Computerised glow curve deconvolution (CGCD) technique and peak shape method. The UV and gamma irradiated phosphors exhibit second order kinetics. The high values of activation energy (~ 3 eV) confirm the trapping of electrons in deep trap centers. The incorporation of doping ions into the host lattice causes non-valence substitutions at the substitutional sites. This increases the number of defects and vacancies in the phosphors and more trap centers were generated. The increased TL intensity and high temperature glow peaks confirm the same. The synthesized phosphors show enhanced TL characteristics, efficient trapping mechanism and low fading effects. These characteristics confirm the suitability of the synthesized phosphors for TL mapping and sensing applications.
关键词： Alkaline earth silicates,Thermoluminscence,Activation energy,Trap depth,Order of kinetics.
更新于2025-09-23 15:23:52
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Low-frequency dielectric spectroscopy and distinct relaxation modes in smectic phases of liquid crystal dimers
摘要： Low-Frequency (LF~20Hz–10MHz) ac field response and relaxation modes are investigated in layered liquid crystalline (LC) smectic phases exhibited by Hydrogen bonded dimers, viz., nOnBA:MA:nOBA’s with sort spacer moiety and long flexible end chains for n=10,11 and 12. Permittivity (ε') and loss (ε'') determined from capacitance and loss factor. Phase transition temperatures (Tc) are determined. Intra-molecular aromatic interaction and storage capacity are evinced by hysteresis behavior. Data of loss ε''(ω) and permittivity ε'r(ω) recorded in smectic phases infers non-Debye type of asymmetric dispersion. Multiple loss peaks in ε''(ω) is argued to involve distinct time scaled relaxations. Relaxation analyzed by Cole-Davidson method. Re-orientation of longitudinal dipole moment μ to the field analyzed. μ is resolved by rigid core, intra-molecular repulsive and flexible end-chain components. Observed distinct time scale response confirms dipolar components. Trends of relaxation frequency, activation energy, loss maxima, dielectric strength and distribution parameter are analyzed in device perspective. Relaxation and order director fluctuations analyzed. ODF suggest the device utility in high temperature smectic phases far away from critical fluctuations.
关键词： Order Director Fluctuations,Relaxation,Permittivity,Resolved dipole moment,Activation energy,Reorientation,Loss
更新于2025-09-23 15:23:52
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Influence of GaN- and Si?N?-Passivation Layers on the Performance of AlGaN/GaN Diodes With a Gated Edge Termination
摘要： This paper analyses the influence of the GaN and Si3N4 passivation (or 'cap') layer on the top of the AlGaN barrier layer on the performance and reliability of Schottky barrier diodes with a gated edge termination (GET-SBDs). Both GaN cap and Si3N4 cap devices show similar dc characteristics but a higher density of traps at the SiO2/GaN interface or/and an increase of the total dielectric constant in the access region result in higher RON-dispersion in GaN cap devices. The leakage current at medium/low temperatures in both types of devices shows two low-voltage-independent activation energies, suggesting thermionic and field-emission processes to be responsible for the conduction. Furthermore, a voltage-dependent activation energy in the high-temperature range occurs from low voltages in the GaN cap devices and limits their breakdown voltage (VBD). Time-dependent dielectric breakdown measurements show a tighter distribution in Si3N4 cap devices (Weibull slope β = 3.3) compared to GaN cap devices (β = 1.8). Additional measurements in plasma-enhanced atomic layer deposition (PEALD)-Si3N4 capacitors with different cap layers and TCAD simulations show an electric field distribution with a strong peak within the PEALD-Si3N4 dielectric at the GET corner, which could accelerate the formation of a percolation path and provoke the device breakdown in GaN cap SBDs even at low-stress voltages.
关键词： Si3N4 cap,GaN cap,AlGaN/GaN Schottky diode,reliability,breakdown voltage,passivation layer,off-state,Activation energy
更新于2025-09-23 15:23:52
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Shallow and deep trap levels in X-ray irradiated β-Ga2O3: Mg
摘要： The results of the investigation of thermostimulated luminescence (TSL) and photoconductivity (PC) of the X-ray irradiated undoped and Mg2+ doped β-Ga2O3 single crystals are presented. Three low-temperature peaks at 116 K, 147 K and 165 K are observed on the TSL glow curves of undoped crystals. The high-temperature TSL peaks at 354 K and 385 K are dominant in Mg2+ doped crystals. The correlation between doping with Mg2+ ions and the local energy levels of the intrinsic structural defects of β-Ga2O3, which are responsible for the TSL peaks and PC, is established. The nature of TSL peaks and the appropriate photoconductivity excitation bands are discussed.
关键词： Photoconductivity,β-Ga2O3,Single crystal,Activation energy,Trap levels,Thermostimulated luminescence
更新于2025-09-23 15:22:29
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Effect of grain size and temperature on DC electrical conductivity of tin oxide nanoparticles synthesized by gel combustion method
摘要： Tin oxide (SnO2) nanomaterials of different grain size have been prepared using gel combustion method by varying the fuel (C6H8O7) to oxidizer (HNO3) molar ratio as a process parameter. The prepared samples were characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscope (EDAX). The XRD patterns showed the formation of single phase Tetragonal rutile structure. The average particle size is found to be in the range of 19–34 nm. SEM images show high porosity in the material. The DC electrical conductivity of SnO2 thick film increases with the temperature significantly from 308K to 670K. The DC electrical conductivity of SnO2 thick film decreases with decrease in grain size due to the effect of surface to volume ratio while activation energy increases with decrease of grain size.
关键词： Thick film,Tin oxide,Activation energy,DC conductivity,Combustion synthesis
更新于2025-09-23 15:22:29
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Trapping Analysis of AlGaN/GaN Schottky Diodes via Current Transient Spectroscopy
摘要： Trapping effects on two AlGaN/GaN Schottky diodes with a different composition of the AlGaN barrier layer were analyzed by current transient spectroscopy. The current transients were measured at a constant bias and at six different temperatures between 25 and 150 °C. Obtained data were fitted by only three superimposed exponentials, and good agreement between the experimental and fitted data was achieved. The activation energy of dominant traps in the investigated structures was found to be within 0.77–0.83 eV. This nearly identical activation energy was obtained from current transients measured at a reverse bias of -6 V as well as at a forward bias of +1 V. It indicates that the dominant traps might be attributed to defects mainly associated with dislocations connected predominantly with the GaN buffer near the AlGaN/GaN interface.
关键词： activation energy,exponential function,Schottky diode,AlGaN/GaN,(de)trapping
更新于2025-09-23 15:22:29
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Effect of Ag incorporation on structural and opto-electric properties of pyrolized CdO thin films
摘要： We have investigated the structure, morphology and opto-electric properties of CdO and Ag-incorporated CdO thin films prepared by chemical spray pyrolysis (CSP) method. The X-ray diffraction (GIXRD) study confirms that CdO samples are highly polycrystalline with cubic structure. The AFM study shows smooth surfaces both for CdO and Ag-CdO thin films. The direct band gap energy varies from 2.25 to 2.50 eV depending on Ag content in the films. Urbach energy reversal in optical band gap indicates that several localized states are present above Fermi level or near at the conduction band. The optical properties, such as refractive index, optical conductivity and nonlinear optical susceptibility, are found dependent on Ag content. A combined effect on the transport properties has been observed with the incorporation of Ag in CdO. The metal-like electric conduction of CdO film has been removed up to a temperature Tc for Ag doping. The n-type carrier concentration of CdO is reduced with increasing Ag content and the concentration is of the order of ~ 1020 cm?3.
关键词： Band gap,Activation energy,Thin films,XRD,Urbach tail
更新于2025-09-23 15:21:21