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In the current study, Sm3+ ions doped Lithium Barium Tungstate (Li2Ba5W3O15) (LBW) phosphors with the ability to emit orange-red light were made using the traditional high-temperature solid-state reaction technique. The structure and phase of the as-synthesized phosphor samples were examined via X-ray diffraction (XRD) patterns. The diffraction peaks of the undoped LBW and Sm3+ ions doped LBW phosphors closely resemble those of the Joint Committee on Powder Diffraction Standards (JCPDS) pattern with card number 01–072-1717. Scanning electron microscopy (SEM) was employed for the analysis of the morphological characteristics of the synthesized phosphor material. Fourier Transform Infrared (FT-IR) spectroscopy was used to study several vibrational and molecular bands present in the host matrix. Using diffuse reflectance spectra (DRS), the optical band gap values (Eg) were evaluated by applying Tauc's method. The photoluminescence (PL) spectra characteristics at λex = 336 nm indicate the emission of dopant ions (Sm3+) in the deep orange-red region corresponding to 4G5/2 → 6H5/2 transition (at 581 nm) with concentration quenching after 2 mol % of Sm3+ ions. Using the PL spectra, the CIE chromaticity coordinates of LBWS2.0 phosphor were estimated and found in the deep visible orange-red area, indicating the potential use of the prepared phosphor material for phosphor-converted white light emitting diodes (w-LEDs) applications. Double exponential behaviour can be seen in the PL decay spectral profiles obtained under λem = 581 nm and λex = 336 nm. The experimental lifetimes (τexp) decrease as the concentration of Sm3+ ions rise. The temperature-dependent PL (TDPL) and activation energy results show that the as-synthesized phosphor has considerably superior thermal stability. The results of the current research contemplate us the applicability of Sm3+ ions doped LBW phosphor for photonic devices such as w-LEDs. [ABSTRACT FROM AUTHOR]

This mixed-method study aimed to evaluate the Teacher Development Project for Local Development (TDPLD) program in northern Thailand from 2016-2020. The aspects of evaluation included outputs, outcomes, and impacts in various dimensions. Ten groups of 3,041 individuals were identified for sampling using voluntary selection, purposive sampling, and snowball sampling techniques. Qualitative research methods were used on 702 participants, while quantitative means were employed on 2,339 informants. The results revealed that before entering the TDPLD development course, individuals exhibited a high level of competency in local development. Further analysis also showed that during each participant's induction period (the period before employment as a teacher), they gained the necessary knowledge that could be used to create tangible learner development. Unfortunately, promises of hometown teaching assignments were sometimes not kept. A common thread throughout the study was the need for English language skills preparation and funding. The study contributes significantly to the literature because it is one of Southeast Asia's most extensive teacher development studies ever undertaken. [ABSTRACT FROM AUTHOR]

Despite the large misfit dislocation densities, indium gallium nitride (InGaN) demonstrates high luminous efficiency both for electroluminescence and photoluminescence. The mechanism behind it has been interpreted as the existence of potential minima (i.e., localized states), which will screen the non-radiative recombination centers to avoid carriers being trapped by the defects. The existence of localized states has been testified by many experiments. However, almost all of the observations are indirect observations, and some experiments, such as those focused on whether the indium clusters observed by transmission electron microscopy are localized states, still remain controversial. Here, we report the direct observation of carrier transportation between localized states driven by temperature-dependent photoluminescence (TDPL) and excitation power-dependent PL in InGaN quantum wells. This enriches the experimental evidence on the existence of localized states. [ABSTRACT FROM AUTHOR]

Despite the large misfit dislocation densities, indium gallium nitride (InGaN) demonstrates high luminous efficiency both for electroluminescence and photoluminescence. The mechanism behind it has been interpreted as the existence of potential minima (i.e., localized states), which will screen the non-radiative recombination centers to avoid carriers being trapped by the defects. The existence of localized states has been testified by many experiments. However, almost all of the observations are indirect observations, and some experiments, such as those focused on whether the indium clusters observed by transmission electron microscopy are localized states, still remain controversial. Here, we report the direct observation of carrier transportation between localized states driven by temperature-dependent photoluminescence (TDPL) and excitation power-dependent PL in InGaN quantum wells. This enriches the experimental evidence on the existence of localized states.

The influence of excessive H _2 flow during barrier growth on optical and electrical properties of InGaN light-emitting diodes (LEDs) are investigated in this study. The room temperature photoluminescence of LEDs decays with excessive H _2 treatment. Temperature-dependent photoluminescence (TDPL) reveals an increase of the density and a decrease of the activation energy of deep non-radiative recombination centers in the H _2 treated LEDs. The external quantum efficiency (EQE) of the LEDs suffers from excessive H _2 treatment. The leakage current on the reverse and forward sides of the LEDs are reduced significantly when treated with H _2 , which may be due to the suppressed Poole–Frenkel effect.

The effect of different growth interruption time on the surface morphology and optical properties of InGaN quantum dots (QDs) grown on 2-inch silicon substrates is investigated. The surface becomes rougher and the photoluminescence intensity has been enhanced significantly when employing the growth interruption method. Temperature-dependent photoluminescence and excitation power-dependent photoluminescence both present unchanged peak energy and line-width of QDs. The sharp increase of PL intensity in medium temperature regime is attributed to the fingerprint of the existence of InGaN QDs. The shape of the QDs are further confirmed by the transmission electron microscopy with a size of 3 nm by 4 nm. Among the samples, a growth interruption time of 30 s gives the best optical performance.

[Display omitted] • PL spectra reveal blue and yellow emission from OFSZBS glasses under 348 nm. • I-H model and Dexter theory reveal dipole–dipole type interaction responsible for quenching. • Temp. dependent PL reveals good thermal stability for Dy doped OFSZBS glasses. • CIE values reveals the usage of OFSZBS:Dy glasses for w-LED applications. Structural, thermal, and photoluminescence (PL) characteristics of a series of Dy3+ doped Oxyfluoride Strontium Zinc Borosilicate (OFSZBS) glasses have been investigated. The XRD of 1.0 mol% Dy3+ ions doped OFSZBS glass and FT-IR investigations conducted on an un-doped as well as all the Dy3+ ions doped OFSZBS glasses confirm the non-crystalline nature and distinct functional groups present in it respectively. The Differential Scanning Calorimetry (DSC) thermogram recorded for an un-doped OFSZBS glass reveals thermal stability (ΔT) and transition temperature (T g). The optical band gaps were computed using the Tau'c method. Under 348 nm pumping wavelengths, the Photoluminescence (PL) spectra of the as-synthesized OFSZBSDy glass samples exhibit blue (450 nm), yellow (575 nm), and red (650 nm) color transitions. The PL intensity increases with Dy3+ ions concentration up to 1 mol% and after that intensity decreases due to the concentration quenching effect. The PL decay profiles reported at higher concentrations were best fitted to the Inokuti-Hirayama (I-H) model for s = 6, indicating the energy transfer process as dipole–dipole in nature. The result obtained from the I-H model is in consonance with that of Dexter's theory. At 448 K, the PL intensity is up to 85% of room temperature, indicating that the as-synthesized glasses have exceptional thermal stability. Relatively higher values of quantum efficiency (η), emission cross-sectional area (σ se), and probability of radiative transition (A R) observed for 1 mol% Dy3+ ions doped OFSZBS glasses declare their suitability in photonic devices under n-UV/blue pumping wavelength. [ABSTRACT FROM AUTHOR]

This paper presents up-to-date side-channel attacks and their countermeasures. A classification of side-channel attacks and countermeasures is done and how to design a model of side-channel attack is presented. A novel transistor-level countermeasure approach, three-phase dual-rail pre-charge logic (TDPL), against side-channel attacks based on analysis of crypto core's leakage currents is explained. Algorithms and models to predict the input vector for maximum and minimum leakage current in CMOS and TDPL gates are reviewed. Extensive transistor level simulations on basic gates implemented in 65 nm CMOS technology are presented and a methodology to analyze this data and compare CMOS vs. TDPL as a possible countermeasures. The results of this study show that leakage current can be easily exploited as a side channel by an attacker to extract information about the secret key in cryptographic hardware in CMOS crypto-design, while TDPL can be a reliable countermeasure to use in future design of smart cards. [ABSTRACT FROM AUTHOR]

• AZABS glasses doped with Eu3+ ions were prepared by melt quench method. • XRD recorded for undoped AZABS glass reveals its amorphous nature. • Intense excitations in UV region reveals utility of UV-LED as an excitation source. • Temp. dependent PL reveals good thermal stability for Eu doped AZABS glasses. • CIE values reveals the usage of AZABS Eu glasses for cool red emission. In this paper we report the synthesis of thermally stable borosilicate glasses doped with europium ions having chemical composition 35B 2 O 3.20SiO 2.(15-x)Al 2 O 3.15ZnO.15Na 2 CO 3.xEu 2 O 3 (x = 0.5 to 2.5 mol%) using melt quench process. A broad hump without any sharp peaks observed in the XRD spectrum recorded for an undoped glass confirm its glassy nature. The DSC & TGA has been conducted on an undoped glass to understand thermal stability and aggregate weight loss. Raman spectrum recorded for an undoped glass reveal various functional groups present in the host glass along with its phonon energy. The absorption spectral features recorded for the as prepared glasses are used to estimate optical band gap. In the process of understanding the effective usage of the as prepared glasses in visible red photonic device applications, the spectral features such as photoluminescence (PL) excitation, PL emission and PL decay were recorded and analyzed. Under 393 nm sharp excitation, all the glass samples are showing red emission corresponds to 5D 0 → 7F 2 transition (612 nm) and whose intensity continuously increasing with Eu3+ ion concentration up to 2.5 mol%. The red to orange color ratio (R/O) estimated from the recorded PL spectral features varies from 3.62 to 3.92 within the variation limits of Eu3+ions from 0.5 to 2.5 mol% indicates relatively low symmetry around Eu3+ ions in the as prepared glasses. Relatively higher R/O ratio also reveals that the nature of bonding between Eu3+ ions and the surrounding ligands as covalent. The Judd-Ofelt theory has been applied to the emission spectral features to understand the nature of bonding between the doped RE ion and its surrounding ligands along with the radiative properties of the doped RE ion. Activation energy (0.175 eV) and percentage loss (82%) in PL intensity estimated for 2.5 mol% of Eu3+ions through temperature dependent PL (TDPL) studies reveal the superiority in thermal stability of the as prepared glasses. The PL, TDPL, PL decay studies conducted along with CIE coordinates estimated allows us to contemplate that, the as prepared glasses are quite useful in fabricating thermally stable visible red photonic devices. [ABSTRACT FROM AUTHOR]