Full Width At The Half Maximum Research Articles

Research on the Dimming Characteristics of Short Arc Ultra-High Pressure Mercury Lamps for Projection Applications

The voltage, current and power are measured for short arc ultra-high pressure mercury lamps (UHP) with rating power 250 W driven by 50 Hz square waveform power supply. It is found that the curve slope of voltage-current characteristics is positive in most of the power range, and negative around 170 W. The photometric, colorimetric and electric parameters are measured with an integrating sphere system couple with a spectrometer in UHP dimming experiments. The results show luminous flux increases with power linearly. The luminous efficacy and color rendering index (CRI) reduce with power reduction because of the decrease of spectral continuum. The mercury pressure are calculated with the full width at the half maximum (FWHM) of 546 nm spectral band, which is 6.2-11.0 nm according to the mercury pressure 15.3-25.8 MPa for UHP power 43-258 W.

Spectral inverse quantum (Spectral-IQ) method for modeling mesoporous systems: application on silica films by FTIR.

The present work advances the inverse quantum (IQ) structural criterion for ordering and characterizing the porosity of the mesosystems based on the recently advanced ratio of the particle-to-wave nature of quantum objects within the extended Heisenberg uncertainty relationship through employing the quantum fluctuation, both for free and observed quantum scattering information, as computed upon spectral identification of the wave-numbers specific to the maximum of absorption intensity record, and to left-, right- and full-width at the half maximum (FWHM) of the concerned bands of a given compound. It furnishes the hierarchy for classifying the mesoporous systems from more particle-related (porous, tight or ionic bindings) to more wave behavior (free or covalent bindings). This so-called spectral inverse quantum (Spectral-IQ) particle-to-wave assignment was illustrated on spectral measurement of FT-IR (bonding) bands’ assignment for samples synthesized within different basic environment and different thermal treatment on mesoporous materials obtained by sol-gel technique with n-dodecyl trimethyl ammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) and of their combination as cosolvents. The results were analyzed in the light of the so-called residual inverse quantum information, accounting for the free binding potency of analyzed samples at drying temperature, and were checked by cross-validation with thermal decomposition techniques by endo-exo thermo correlations at a higher temperature.

Diode-pumped passively mode-locked Nd:KLu(WO4)2 laser

A diode-end-pumped mode-locked laser based on Nd:KLu(WO4)2 crystal is demonstrated for the first time. The central wavelength is 1070.2nm and the spectral width is 0.20nm. The obtained maximum average output power is 1.4W and the corresponding conversion efficiency from the absorbed pump power to the 1070.2nm laser is 31.8%. The full width at the half maximum (FWHM) of the autocorrelation trace is about 16ps. If a Gauss-pulse shape is assumed, the pulse duration is 11ps. The repetition rate is 102MHz.

The Effects of Substrate Surface Treatments on Growth of a-Plane GaN Single Crystals Using Na Flux Method

Nonpolar GaN substrates are necessary for the improvement of GaN device performance. The growth of high-quality nonpolar GaN crystals, however, has not yet been achieved. In this study, we grew a-plane GaN crystals using the Na flux method and investigated the effects of the substrate surface treatment on the crystallinity of grown GaN crystals. A-plane GaN substrates with chemical mechanical polishing (CMP) and with chemical etching using pyrophosphoric acid were used as the seed substrates. We found that full width at the half-maximum (FWHM) of the X-ray rocking curve (XRC) of GaN crystals grown on the substrate with chemical etching was smaller than that on the substrate with CMP. The results show that chemical etching is more effective than CMP for improving the crystallinity of a-plane GaN crystals.

Intermetallic compound spalling characteristics of Sn-3.5Ag solder over ternary electroless Ni under-bump metallurgy

Abstract

High-Temperature Sensor Based on Neutron-Irradiated 6H-SiC

Nitrogen-doped 6H-SiC single crystals irradiated with neutrons up to a fluence of 5.74×1018 n/cm2 at the temperature of 60-80°C were investigated by means of X-ray diffractometer and metallurgical microscope. The experimental results showed the X-ray diffraction peak (0006) was broadened due to the lattice distortion resulting from irradiation-induced defects, and then narrowed linearly when isochronally annealed over the temperature of 700°C. Meanwhile, from the chemical etching photomicrographs, the characteristic was accompanied by the changes of the dislocation density after the process of irradiation and post-irradiation annealing. According to this characteristic of irradiated 6H-SiC crystals, a novel temperature sensor suitable for the temperature range of 700-1300°C or more is developed, which depends on the linear relationship between XRD FWHM (the full width at the half maximum of X-ray diffraction peak) and isochronal annealing temperature over about 700°C. The subsequent application test demonstrated that the sensor remained no damage in the very harsh conditions as well as possessed a less than +5% of the relative temperature error. Therefore, the neutron-irradiated 6H-SiC can be employed as a kind of non-invasive temperature measurement sensor to determine the temperature of closed, high-speed rotating and difficult-to-access parts on a running machine such as internal-combustion engine pistons, turbine blades and so on.

Solid-State Slit Camera (SSC) Aboard MAXI

The Solid-state Slit Camera (SSC) is an X-ray camera aboard the MAXI mission of the International Space Station. Two sets of SSC sensors view the X-ray sky using charge-coupled devices (CCDs) in the 0.5–12 keV band. The total area for X-ray detection is about 200 cm|$^2$|⁠, which is the largest among the missions of X-ray astronomy. The energy resolution at the CCD temperature of |$-$|70|$^{\circ}$|C is 145 eV in full width at the half maximum (FWHM) at 5.9 keV, and the field of view is 1|$^\circ\!\!\!.$|5 (FWHM) |$\times$| 90|$^{\circ}$| for each sensor. The SSC could make a whole-sky image with the energy resolution good enough to resolve line emissions, and monitor the whole-sky at the energy band of |$\lt\ $|2 keV for the first time in these decades.

Ultrabroad near-infrared photoluminescence from Bi5(AlCl4)3 crystal

The Bi5(AlCl4)3 crystal, synthesized by a environmentally friendly room-temperature method using ionic liquids as reaction solvents, exhibits extremely broad near-infrared photoluminescence (PL) with a full width at the half maximum (FWHM) of >510 nm and an effective PL lifetime of 4.1 µs at 1160 nm. We envision that this study not only extends the understanding of photophysical properties of materials containing subvalent bismuth, but also may have promise for the design of novel photonic materials containing a wide array of p-block elements.

Fabrication and Optical Properties of Monodisperse Fine Zinc Oxide Nanorods

Highly monodisperse ZnO nanorods were synthesized by simple solution chemical process. The produced ZnO nanorods have uniform diameters about 30 nm with average aspect ratios more than 40. Raman and photoluminescence measurements were used to examine their optical properties. Raman spectrum presents weak quantum confinement effects of the fine nanorods. Laser power-dependent photoluminescence spectra show the products have intense UV emissions with narrow full width at the half maximum (FWHM). All the performed experiments determine the good crystal and optical quality of synthesized nanorods.

CMOS 공정에 적합한 AlN 압전 마이크로 발전기의 제작 및 특성

This paper describes the fabrication and characteristics of AlN piezoelectric MPG(micro power generator). The micro energy harvester was fabricated to convert ambient vibration energy to electrical power as a AlN piezoelectric cantilever with Si proof-mass. To be compatible with CMOS process, AlN thin film was grown at low temperature by RF magnetron sputtering and micro power generators were fabricated by MEMS technologies. X-ray diffraction pattern proved that the grown AlN film had highly(002) orientation with low value of FWHM(full width at the half maximum, $\theta

A High-Sensitivity Small-Animal PET Scanner: Development and Initial Performance Measurements

An important challenge in positron emission tomography (PET) is the development of dedicated small-animal PET (muPET) systems having high sensitivity. In this paper, we investigate the use of an opposing pair of large-area detectors having high detection efficiency and moderate depth-of-interaction resolution in a compact scanner geometry for achieving a high system sensitivity. Substantial resolution degradations created by this hardware configuration, on the other hand, are corrected for by applying model-based image reconstruction. We have developed a prototype scanner adopting this design and evaluated its performance properties. Our results show that the prototype can achieve a central sensitivity of ~28.2% when using an energy window (EW) of 250-750 keV and a coincidence time window (CW) of 10 ns. When decreasing the EW to 400-750 keV, the central sensitivity still remains high at ~14.4%. Over the typical ranges of radioactivity used in PET rodent imaging with [18F]fluorodeoxyglucose (FDG), the prototype provides noise-equivalent count rates (NECRs) that are considerably higher than other muPET systems. For a mouse/rat-sized cylinder, we obtain a peak NECR of ~ 1.86/1.2 Mcps at ~32/40 MBq when using a 250/350-750 keV EW and a 6 ns CW. Using a resolution phantom, we obtain an average FWHM (full width at the half-maximum) of 1.79 mm for 1.35 mm-diameter rod sources when the axis of the phantom is vertical to the detectors of the prototype. This is consistent with the 1.2 mm FWHM image resolution previously obtained by using simulation data. The prototype also generates FDG rat images having good visual quality.

Synthesis and characterization of fluorene‐based rod–coil liquid crystal polymers

AbstractA series of fluorene‐based rod–coil liquid crystal polymers with different lengths of the coil segments on backbones were designed and synthesized by a palladium‐catalyzed Suzuki coupling‐reaction. The thermal stability, the UV–Vis absorption and fluorescence spectra in chloroform solution and thin film, the electrochemical properties, thermal behavior, and morphology of these rod–coil polymers were investigated. The thermal stability of these polymers steadily decreased on increasing the length of the coil segments on the backbone; their optical and electrochemical properties did not exhibit noticeable dependence on the weight fraction of the coil segments. However, the shoulder emission and the full width at the half‐maximum (FWHM) in PL spectra of the films increased, whereas the oxidation onset potentials and the corresponding HOMO energy levels decreased with the increase in the weight fraction of the coil segments, which was assigned to microphase separation and formation of folded chain conformation as the weight fraction of the coil segments increased. These polymers displayed a characteristic liquid crystalline texture. The variation of the weight fraction of the coil segments obviously affected the thermal behavior and morphology of these rod–coil polymers. Copyright © 2008 John Wiley & Sons, Ltd.

Optimization of Zn 1− xAl xO film for antireflection coating by RF sputtering

The structural, optical and electrical properties of the Zn 1− x Al x O films deposited by RF magnetron sputtering have been investigated. The films of different concentration ( x = 0.005, 0.01, 0.02, 0.04) deposited on Si (1 0 0) have been characterized using X-Ray diffraction (XRD), Reflectance and Hall effect measurements. From XRD analysis, it has been inferred that all the films are single crystalline with (0 0 2) preferred orientation and higher Full Width at the Half Maximum (FWHM) for 4 mol.% Al-doped ZnO (i.e., x = 0.04). Reflectance measurement suggests that the optimized concentration of Zn 0.96Al 0.04O film can be used as an antireflection coating for the solar cell as it exhibits the low reflectivity. The Hall measurements reveal that the electron concentration is found to be increasing with Al concentration and it has been maximum, 7.582 × 10 20/cm 3 for Zn 0.96Al 0.04O with low resistivity of 0.0851 Ωcm.

Assessment of Fatigue Life for High-Temperature Pipeline Welds Using X-Ray Diffraction Technique

The objective of this study is to examine the feasibility of the X-ray diffraction method for the fatigue life assessment of high-temperature steel pipes used for main steam pipelines, re-heater pipelines and headers etc. in power plants. In this study, X-ray diffraction tests were performed on the specimens simulated for low cycle fatigue damage, in order to estimate fatigue properties at the various stages of fatigue life. As a result of X-ray diffraction tests, it was confirmed that the full width at the half maximum (FWHM) decreased with an increase in the fatigue life ratio, and that the FWHM and the residual stress due to fatigue damage were algebraically linearly related to the fatigue life ratio. From this relationship, a direct assessment of the remaining fatigue life was feasible.

Structural properties of pulsed laser deposited zinc oxide thin films annealed at various temperatures

Zinc oxide (ZnO) thin films were prepared by pulsed laser deposition (PLD) technique using XeCl excimer laser with a wavelength of 308 nm at room temperature on quartz and single crystal silicon (100) substrates. The oxygen gas pressure was set at 6 torr during the deposition. The deposited films were post-heat treated (HT) in air at different annealing temperatures (ATs) for 30 min. The X-ray diffraction (XRD), optical and electrical properties were measured to study the properties of the films as a function of AT. XRD analysis showed that the strength of (002) peak increases and full width at the half maximum (FWHM) value decreases as the AT increases from 200 to 600°C. The films HT at higher AT of ∼600°C showed dominant c axis oriented hexagonal wurtize crystal structure. The films HT at 600°C exhibit high average transmittance of ∼85% in the visible region and very sharp absorption edge at 376 nm with energy band gap of ∼3·46 eV. Electrical measurement indicates that the resistivity of films decreases with the AT up to 600°C, after which there is an increase at higher AT. The complex of hydrogen defect and oxygen vacancy in the ZnO films may be the reason for low conductivity in undoped ZnO films.

Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films

In this paper, we present and analyse the optical characteristics, such as spectral shift, CIE coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency, of an organic light-emitting device (OLED) with a commercial diffuser film or a brightness-enhancement film (BEF) attached. Compared to a planar green OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 29% and 23%, respectively. The overall luminous power efficiencies are enhanced by 28% and 7%. Compared to the planar green device, we observe blue shifts at different viewing angles when microstructured films are attached, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifts and the full width at the half maximum (FWHM) decrease with increasing viewing angles due to the microcavity effect. When the diffuser is attached, the spectral peak has a constant blue shift (6nm) compared to that of the planar OLED. On the other hand, in the BEF case, the spectral shift depends on the viewing angle (2–12nm blue shifts from 0 to 80°). This is due to the different operating principles (scattering and redirected light) of the diffuser and BEF. Since the transmittance spectra of both the diffuser film and the BEF are flat over the visible range, it is suitable for lighting applications by using white OLED. When attaching the films on a commercial white OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 34% and 31%, respectively. The overall luminous power efficiencies are enhanced by 42% and 8%.

Investigation of ZnO films on Si substrate grown by low energy O + assisted pulse laser deposited technology

Zinc oxide thin films (ZnO) with different thickness were prepared on Si (111) substrates using low energy O + assisted pulse laser deposition (PLD). The structural and morphological properties of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements, respectively. The quality of ZnO films was also examined by using Rutherford backscattering spectroscopy/ion channeling (RBS/C) techniques. XRD showed that there was only one sharp diffraction peak at 2 θ = 34.3° with the full width at the half maximum (FWHM) of around 0.34° for two ZnO samples, which also indicated that ZnO thin films had a good c-axis preferred orientation. Results of Rutherford backscattering and ion channeling clearly indicated that the Zn:O ratio in zinc oxide thin film approached to unity and the ZnO thin film grown by low energy O + assisted pulse laser deposition had a polycrystalline structure. In the case of ZnO film fabricated by low energy O + assisted pulse laser deposited under identical experimental conditions except growth time, AFM analysis has shown that the root mean square (RMS) roughness (2.37 nm) of thinner ZnO film (35 nm) was far below that (13.45 nm) of the thicker ZnO film (72 nm).

6H-SiC Homoepitaxial Growth and Optical Property of Boron- and Nitrogen-Doped Donor-Acceptor Pair (DAP) Emission of 1º-Off Substrate by Closed-Space Sublimation Method

We demonstrate high-speed and high-quality 6H-SiC homoepitaxial growth on a 1°-off c-plane SiC substrate by a closed-space sublimation method. By optimizing the size of single-crystal source materials in the growth system, a high-quality 6H-SiC epilayer with an X-ray diffraction rocking curve (0006) full-width at the half maximum (FWHM) of 38 arcsec was obtained. We also carried out doping of nitrogen and boron during the growth of the SiC epilayer. A strong donor-acceptor pair (DAP) emission at a peak wavelength of 570 nm under excitation by a 395 nm nitride-based light-emitting diode (LED) was observed. The 6H-SiC with DAP emission is promising for use as a phosphor in a nitride-based LED, because high-quality nitride layers can be grown on the SiC substrates with small off-oriented angles.

A Raman scattering study of structural changes in LaMn 1− xCo xO 3+ δ system

We present results of Raman scattering studies on LaMn 1− x Co x O 3+ δ over a wide range of doping content ( x = 0.1–0.75) and temperature range of 20–300 K. Powder X-ray diffraction patterns show that there is a structural change from orthorhombic to rhombohedral at x = 0.5 as x increases. Raman spectra of all LaMn 1− x Co x O 3+ δ samples show peaks near 260, 500, and 650 cm −1. However, the Raman spectra are not drastically different from each other across the structural phase transition at x = 0.5. On the other hand, the peak frequencies of the modes near 260 and 500 cm −1 as functions of Co content ( x) show slope changes at x = 0.5. The full-width at the half-maximum (FWHM) of the mode near 650 cm −1 as a function of Co content ( x) shows minimum at x = 0.5. Normally, larger values of FWHM are expected at near x = 0.5, if the mode were affected by the structural disorder at the phase boundary. Therefore, it is likely due to lowest charge concentration at x = 0.5, which results in lowest screening effect. This is consistent with the fact that the intensity of the phonons is strongest at x = 0.5. As the temperature decreases, the two peaks near 500 and 650 cm −1 of different Co contents, related with octahedral distortions, are found to shift to lower frequencies unlike the usual temperature behavior. However, no abrupt change in the peak frequencies and the FWHM is observed across measured temperature range, regardless of the Co content.

Residual stress evolution with compressive plastic deformation in 6061Al–15 vol.% SiC w composites as studied by neutron diffraction

The evolution of the residual stress (RS) with compressive plastic deformation of several discontinuously reinforced 6061Al–15 vol.% SiC w metal–matrix composites (MMCs) has been investigated. The composites were obtained by a powder metallurgical route and heat treated to a fully hardened, T6 condition. The RS was determined from neutron diffraction. The results show that deformation relaxes the hydrostatic component of the macroscopic RS (M-RS) progressively until a minimum is reached, around 2–5% plastic strain. Similarly, the hydrostatic component of the microscopic RS (m-RS) relaxes rapidly with deformation. Relaxation continues with further strain and at ≈15% this m-RS component disappears. The deviatoric components of both the M-RS and the m-RS, however, remain unaltered with increasing plastic strain. The increase of the full width at the half maximum (FWHM) of the Al diffraction peaks with strain reveals the increased lattice distortion and microscopic RS gradient around the reinforcing particles. The linear correlation found between the FWHM of the two phases suggests also the activation of a lattice distortion transfer mechanism from the Al phase to the SiC phase.