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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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Luminescence and dielectric properties of Ni2+ ions added to calcio yttria borophosphate glasses for optoelectronic uses
摘要： Glass materials of composition CaO – Y2O3 – B2O3 – P2O5 added with different concentrations of NiO (Ni2+: CYBP) are synthesized by conventional rapid melt quenching method. Various physical properties of these glasses such as polaron radius (rp), molar volume (Vm), optical basicity (Λth) and refractive index (μ) are studied. As an elastic characterization Young’s modulus (Y), Poison ratio (σ) and micro hardness (H) of these glasses are studied. These grades suggest that the prepared materials are mechanically hard and exhibiting covalently interlinked structure. Further these samples are characterized by various techniques such as differential thermal analysis, thermoluminiscence, optical absorption, photoluminescence, Ionic conductivity and dielectric dispersion. The thermoluminiscence grades such as peak temperature maximum (Tm), shape symmetry factor (μsf) and activation energies ( Eτ, Eδ and Eω) are studied at various UV irradiation levels. These results strongly recommended that the both electron and hole trap centers were created at the deeper trap levels and contribute higher orders of thermoluminiscence emission with in these glasses subjected to higher orders of temperature and UV irradiation. The various optical absorption and photoluminescence factor's such as, optical band gap (Eo), nephelauxetic ratio (β), emission cross section (Ω), branching ratio (ζ) and radiative life times (τ) are studied. These grades found to be maximum for the material which has 0.5 mol% of NiO concentration may be most suggestible for optoelectronic application. The dc and ac conductivity (σdc & σac) of these glasses are estimated. The various dielectric parameter’s such as loss tangent (Tan (φ)), temperature region of relaxation (ΔT), density of states near Fermi level (N(Ef)), activation energies of both dipoles and conduction (Ed & Ec) are also calculated. These reports clearly disclose that the octahedrally located Ni2+ ions are increasing with increase NiO concentration with in present calcio yttria borophosphate glasses.
关键词： emission cross section,nephelauxetic ratio,micro hardness,trap depth parameters,Ni2+: CYBP glass materials,temperature region of relaxation
更新于2025-09-19 17:15:36
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Predicting the afterglow duration in persistent phosphors: a validated approach to derive trap depth distributions
摘要： Persistent phosphors are increasingly investigated due to their potential applications in various fields, such as safety signage, dosimetry and in vivo imaging. These materials act as optical batteries that store and gradually release energy supplied during optical charging. As the energy is stored, or ‘trapped’, at specific defect sites in the host lattice, a clear understanding of the defects and trapping mechanisms in these materials is important for systematic improvement of their properties. Here, the thermoluminescence and afterglow properties of the near-infrared (NIR) emitting persistent phosphor LiGa5O8:Cr3+ (LGO:Cr) are studied. This phosphor is used as a model system for illustrating a more general approach to reliably derive trap depth distributions in persistent luminescent and storage materials. The combination of the Tstop–Tmax method with initial rise analysis is used to experimentally determine the presence of a broad distribution of trapping states. Computerized glow curve fitting is subsequently used to extract the relevant trapping parameters of the system in a rigorous, consistent manner, by fitting all the experimentally recorded data simultaneously. The resulting, single set of model parameters is able to describe all measured thermoluminescence and afterglow data and hence can be used to predict afterglow and storage properties of the phosphor under various conditions. The methods to analyze and describe the trap structure of the persistent phosphor LGO:Cr are straightforwardly applicable for other persistent and storage phosphors and result in a reliable determination of the relevant trapping parameters of a given material.
关键词： thermoluminescence,afterglow,persistent phosphors,LiGa5O8:Cr3+,trap depth distributions
更新于2025-09-19 17:15:36
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Three-dimensional device simulation of random telegraph noise spectroscopy with Coulomb energy variation of the trap in high- <i>k</i> gate oxide
摘要： The random telegraph noise (RTN) time constants, capture (τc) and emission (τe) times, have been extensively used to identify the trap position in the gate oxide by comparing the measured τc-over-τe ratio with the Shockley–Read–Hall (SRH) statistics. However, various factors have been shown to affect the accuracy of the extracted trap depth from the SRH-type models, such as three-dimensional (3D) device electrostatics, atomistic doping, metal gate granularity, and Coulomb energy variation (CEV) of the trap. Focusing on CEV in this work, we assume the trap in gate oxide can be regarded as a floating island and then numerically studied the CEV of the trap with 3D drift-diffusion simulation. Analyzing the simulation data, the extracted trap depth without considering CEV in the SRH statistics are quantitatively compared with the data involved CEV.
关键词： CEV,trap depth,3D device simulation,RTN,random telegraph noise,Coulomb energy variation,high-k gate oxide
更新于2025-09-10 09:29:36