Properties of 80-MeV oxygen ion irradiated ZnS:Mn nanoparticles and exploitation in nanophotonics

ZnS:Mn nanoparticles of size variation 11–17 nm were synthesized by a simple and inexpensive chemical method and confirmed by transmission electron microscopy (TEM). Presuming electronic energy loss (S _e>S _n, S _n being nuclear energy loss) to be the dominant phenomenon, they were irradiated by 80-MeV energetic oxygen ions with fluence of 10¹¹ to 10¹³ ions/cm². Photoluminescence (PL) spectra revealed three major emission bands ~445 nm, ~582 nm and ~706 nm; which are ascribed to D–A pair transition, Mn emission and surface state led fluorescence activation. The recovery of Mn emission and tunable surface state emission have been observed with ion fluence variation. Infra-red (IR) spectra of irradiated samples show great extent of oscillation with respect to amplitude due to ion fluence variation however, phonon energy (~98 MeV) remains unchanged. The possible applications of these modified properties in nanophotonics are also highlighted.     

Structural and photoluminescence properties of Si nanoclusters obtained by ion implantation into Si3N4 films

In the present paper we report structural and photoluminescence (PL) results from samples obtained by Si implantation into stoichiometric silicon nitride (Si₃N₄) films. The Si excess was introduced in the matrix by 170 keV Si implantation performed at different temperatures with a fluence of Φ=1×10¹⁷ Si/cm². The annealing temperature was varied between 350 and 900 °C in order to form the Si precipitates. PL measurements, with a 488 nm Ar laser as an excitation source, show two superimposed broad PL bands centered around 760 and 900 nm. The maximum PL yield is achieved for the samples annealed at 475 °C. Transmission electron microscopy (TEM) measurements show the formation of amorphous nanoclusters and their evolution with the annealing temperature.     

Europium(III) Concentration Effect on the Spectroscopic and Photoluminescent Properties of BaMoO4:Eu

BaMoO₄:Eu (BEMO) powders were synthesized by the polymeric precursor method (PPM), heat treated at 800 °C for 2 h in a heating rate of 5 °C/min and characterized by powder X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FTIR) and Raman spectroscopy, besides room temperature Photoluminescence (PL) measurements. The emission spectra of BEMO samples under excitation of 394 nm present the characteristic Eu³⁺ transitions. The relative intensities of the Eu³⁺ emissions increase as the concentration of this ion increases from 0.01 to 0.075 mol, but the luminescence is drastically quenched for the Ba_0.855Eu_0.145MoO₄ sample. The one exponential decay curves of the Eu^{3+ 5}D₀→⁷F₂ transition, λ _exc = 394 nm and λ _em = 614 nm, provided the decay times of around 0.54 ms for all samples. It was observed a broadening of the Bragg reflections and Raman bands when the Eu⁺³ concentration increases as a consequence of a more disordered material. The presence of MoO₃ and Eu₂Mo₂O₇ as additional phases in the BEMO samples where observed when the Eu³⁺ concentration was 14.5 mol%.     

Time-resolved luminescence spectroscopy of pure and doped with Ce3+ ions SrAlF5 crystals

The results of a study of time-resolved photoluminescence (PL) and energy transfer in both pure and doped with Ce³⁺ ions SrAlF₅ (SAF) single crystals are presented. The time-resolved and steady-state PL spectra in the energy range of 1.5–6.0 eV, the PL excitation spectra and the reflectivity in the energy range of 3.7–21 eV, as well as the PL decay kinetics were measured at 8.8 and 295 K. The lattice defects were revealed in the low temperature PL spectra (emission bands at 2.9 and 4.5 eV) in the undoped SAF crystals. The luminescence spectra of the doped Ce³⁺:SAF crystals demonstrate a new selective emission bands in the range of 3.7–4.5 eV with the exponential decay kinetics (τ ≈ 60 ns at X-ray excitation). These bands correspond to the d-f transitions in Ce³⁺ ions, which occupy nonequivalent sites in the crystal lattice.     

Structural and optical properties of Ge nanocrystals obtained by hot ion implantation into SiO2 and further ion irradiation

In this work, SiO₂ layers containing Ge nanocrystals (NCs) obtained by the hot implantation approach were submitted to an ion irradiation process with different 2 MeV Si⁺ ion fluences. We have investigated the photoluminescence (PL) behavior and structural properties of the irradiated samples as well as the features of the PL and structural recovery after an additional thermal treatment. We have shown that even with the highest ion bombardment fluence employed (2×10¹⁵ Si/cm²) there is a residual PL emission (12% from the original) and survival of some Ge NCs is still observed by transmission electron microscopy analysis. Even though the final PL and mean diameter of the nanoparticles under ion irradiation are independent of the implantation temperature or annealing time, the PL and structural recovery of the ion-bombarded samples have a memory effect. We have also observed that the lower the ion bombardment fluence, the less efficient is the PL recovery. We have explained such behavior based on current literature data.     

Exciton localization behaviour in different well width undoped GaN/Al0.07Ga0.93N nanostructures

We report results from optical spectroscopy such as photoluminescence (PL) and time resolved photo-luminescence (TRPL) techniques from different well width MOCVD grown GaN/Al_0.07Ga_0.93N MQW samples. There is evidence of localization at low temperature in all samples. The decay time of all samples becomes non-exponential when the detection energy is increased with respect to the peak of the emission. Localization of carriers (excitons) is demonstrated by the “S-shape” dependences of the PL peak energies on the temperature. The time-resolved PL spectra of the 3-nm well multi quantum wells reveal that the spectral peak position shifts toward lower energies as the decay time increases and becomes red-shifted at longer decay times. There is a gradient in the PL decay time across the emission peak profile, so that the PL process at low temperatures is a free electron-localized hole transition.     

Thermo,Iono and photoluminescence properties of 100 MeV Si7+ ions bombarded CaSiO3:Eu3+ nanophosphor

This paper reports on the thermo (TL), iono (IL) and photoluminescence (PL) properties of nanocrystalline CaSiO₃:Eu³⁺ (1–5 mol %) bombarded with 100 MeV Si⁷⁺ ions for the first time. The effect of different dopant concentrations and influence of ion fluence has been discussed. The characteristic emission peaks ⁵D₀→⁷F_J (J=0, 1, 2, 3, 4) of Eu³⁺ ions was recorded in both PL (1×10¹¹–1×10¹³ ions cm^?2) and IL (4.16×10¹²–6.77×10¹² ions cm^?2) spectra. It is observed that PL intensity increases with ion fluence, whereas in IL the peaks intensity increases up to fluence 5.20×10¹² ions cm^?2, then it decreases. A well resolved TL glow peak at ～304 °C was recorded in all the ion bombarded samples at a warming rate of 5 °C s^?1. The TL intensity is found to be maximum at 5 mol% Eu³⁺ concentration. Further, TL intensity increases sub linearly with shifting of glow peak towards lower temperature with ion fluence.     

Luminescence and defect studies of YAlO3:Dy3+, Sm3+ single crystals exposed to 100 MeV Si7+ ion beam

Ionoluminescence (IL) and photoluminescence (PL) spectra for different rare earth ions (Sm³⁺ and Dy³⁺) activated YAlO₃ single crystals have been induced with 100 MeV Si⁷⁺ ions with fluence of 7.81×10¹² ions cm^?2. Prominent IL and PL emission peaks in the range 550–725 nm in Sm³⁺ and 482–574 nm in Dy³⁺ were recorded. Variation of IL intensity in Dy³⁺ doped YAlO₃ single crystals was studied in the fluence range 7.81×10¹²–11.71×10¹² ions cm^?2. IL intensity is found to be high in lower ion fluences and it decreases with increase in ion fluence due to thermal quenching as a result of an increase in the sample temperature caused by ion beam irradiation. Thermoluminescence (TL) spectra were recorded for fluence of 5.2×10¹² ions cm^?2 on pure and doped crystals at a warming rate of 5 °C s^?1 at room temperature. Pure crystals show two glow peaks at 232 (Tg₁) and 328 °C (Tg₂). However, in Sm³⁺ doped crystals three glow peaks at 278 (Tg₁), 332 (Tg₂) and 384 °C (Tg₃) and two glow peaks at 278 (Tg₁) and 331 °C (Tg₂) in Dy³⁺ was recorded. The kinetic parameters (E, b s) were estimated using glow peak shape method. The decay of IL intensity was explained by excitation spike model.     

Decay rate measurements of upper laser level in He-Cd+ laser

The decay rate of² D _5/2 level of Cd II has been measured by the magnetic-field power-dip method. The decay rate at the zero-pressure limit is found to be 2.4·10⁶s⁻¹. The calculated collision cross section for excited Cd ions with He atoms equals 0.91·10⁻¹⁵ cm². This work was supported by the Institute of Quantum Electronics. WAT Warszawa, within the project 06.2.3.     

X-ray determination of thermal expansion of cadmium fluoride and lead fluoride

The lattice parameters of CdF₂ andβ-PbF₂ have been determined over the temperature range 300–670 K. The coefficient of expansion at room temperature is 21·3 × 10⁻⁶ K⁻¹ and 25·4 × 10⁻⁶ K⁻¹ for CdF₂ and PbF₂ respectively and it increases linearly with temperature over the range of temperature covered. The Grüneisen parameter decreases with temperature in both the crystals.     

XUV generation from plasma produced by a XeCl excimer laser on a Cu target

Summary We present a detailed study of XUV and soft X-ray emission from Cu plasma produced by an excimer laser at intensitiesI _L≦8·10¹¹ W/cm². The XeCl excimer laser (ψ≈308 nm) delivers pulses with energyE _L≈2.3 J, temporal durationt _L≈100 ns and brightnessB≧10¹⁴ W/cm² sr. We recorded a spectral conversion efficiency η=0.5% eV⁻¹ forI _L=4·10¹¹W/cm² in the aluminium window at 73eV with a harder X-ray tail around ≈400eV. We also measured the dependence of X-ray signal on laser intensity and viewing angle. Experimental results have been compared with some analytical laser-plasma interaction models.     

注入Ar+的蓝宝石晶体退火前后光致发光谱的分析

对注入Ar⁺后不同晶面取向的蓝宝石晶体在不同退火条件下的光致发光谱进行了分析.分析结果表明:三种晶面取向的蓝宝石样品经Ar⁺注入后,其光致发光谱中均出现了新的位于506nm处的发光峰;真空和空气气氛下的退火均对样品在506nm处的发光有增强作用,不同晶面取向的样品发光增强程度不同,且发光增强至最大时的退火温度也不同,空气气氛下的退火使样品发光增强程度更为显著.由此可以看出,退火气氛、退火温度和晶面取向均对样品发光峰强度有影响. 关键词： 2O₃')" href="#">Al₂O₃ 离子注入 退火 光致发光谱     

Low-flux neutron irradiation of ceramic YBa2 Cu3O7−δ

Summary Pellets of sintered YBa₂Cu₃O_7−δ with three different oxygen contents have been irradiated with fast neutron beams of energies 6.5, 3.3 and 4.4 MeV at fluences of 7.7·10⁴, 1.3·10⁵ and 1.4·10⁹ n/cm², respectively. The radiation damage has been investigated by comparing the critical temperature (T _c ^mid ), the zero resistivity and the onset temperature before and after neutron irradiation. The critical current has been measured for a few samples in the same experimental conditions. In all transport measurements two different responses to the neutron radiation are observed and discussed.     

Luminescent properties of YVO4:Eu/SiO2 core–shell composite particles

We report an efficient process for preparing monodisperse SiO₂@Y_0.95Eu_0.05VO₄ core–shell phosphors using a simple citrate sol–gel method and without the use of surface-coupling silane agents or large stabilizers. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the resulting SiO₂@Y_0.95Eu_0.05VO₄ core–shell phosphors. The XRD results demonstrate that the Y_0.95Eu_0.05VO₄ particles crystallization on the surface of SiO₂ annealing at 800 °C is perfectly and the crystallinity increases with raising the annealing temperature. The obtained core–shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 500 nm and an average thickness of ~50 nm), are not agglomerated, and have a smooth surface. The thickness of the YVO₄:Eu³⁺ shells on the SiO₂ cores could be easily tailored by changing the mass ratio of shell to core (W = [YVO₄]/[SiO₂]) (~50 nm for W = 30%). The Eu³⁺ shows a strong PL luminescence (dominated by ⁵D₀ − ⁷F₂ red emission at 618 nm) under the excitation of 320 nm UV light. The PL intensity of Eu³⁺ increases with increasing the annealing temperature and the values of W.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

Improvement of the pinning properties of (Bi/Pb)-2223 textured ceramics by columnar defects introduced by 6 GeV Pb ions

Pinning properties of (Bi/Pb)-2223 textured ceramics have been improved by 6 GeV Pb ions irradiation. Two samples were irradiated at fluencesφ _t=5 × 10¹⁰ ions/cm² and 2 × 10¹¹ ions/cm², respectively. The magnetic irreversibility is clearly improved in the intermediate range of temperature: (30–35) K<T<60 K for magnetic fields lower than the “fluence equivalent field”B _φ =φ _t.φ ₀. Moreover the irreversibility line is shifted towards higher fields. The results reported here show that the introduction of columnar defects or other extended defects is a route to improve the screening properties of tubes or cans based on (Bi/Pb)-2223 material and operating in liquid nitrogen.     

Thermal and optical properties of Tm<Superscript>3+</Superscript>:NaLa(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> crystal

A Tm³⁺-doped NaLa(WO₄)₂ single crystal with a dimension of Φ20 mm×40 mm was grown by the Czochralski method. Anisotropic thermal expansion coefficients of this crystal were investigated. Polarized absorption spectra, emission spectra and decay curve were recorded at room temperature. The absorption and emission cross-section were presented. Based on the Judd–Ofelt analysis, we obtained the three intensity parameters: Ω₂=10.21×10^-20, Ω₄=2.66×10^-20, and Ω₆=1.46×10^-20 cm². The radiative probabilities, radiative lifetimes, and branch ratios of Tm³⁺:NaLa(WO₄)₂ were calculated, too. Luminescence lifetime of the ³ H ₄ level was measured to be 220 μs. The stimulated emission cross-section for the ³ F ₄→³ H ₆ transition were determined using the reciprocity method, potential laser gain for this transition were also investigated, the gain curves implied that the tunable range is up to 200 nm. PACS 42.70.Hj; 78.20.-e     

Kinetics of formation of O2(1Σ) molecules in reactions involving excited O2(1Δ) oxygen molecules and I(2P1/2) iodine atoms

The results of our experimental study of the kinetics of formation of O₂(¹Σ) molecules in energy-exchange reactions O₂(¹Δ) + I(⁵ p,² P _1/2) and O₂(a,¹Δ) + O₂(a,¹Δ) are presented. The ratio of rate constants was obtained for these reactions (4800 ± 300). Setting the rate constant of the deactivation of O₂(¹Σ) molecules on CO₂ molecules at 4.1 · 10^–13 cm³/s, we evaluated the rate constants for these reactions at a temperature of approximately 330 K: (1.7 ± 0.2) · 10⁻¹³ and (3.6 ± 0.5) · 10⁻¹⁷ cm³/s, respectively.     

Intense green-emitting Sr2LiSiO4F:Eu2+ phosphor for n-UV white LEDs

Eu²⁺-activated Sr₂LiSiO₄F phosphors were synthesized at 900°C by solid-state reaction in reducing atmosphere, and their photoluminescence (PL) properties were systematically investigated by diffuse reflection spectra, PL excitation and emission spectra, and by the fluorescence decay curve. Sr₂LiSiO₄F:Eu²⁺ emits intense green light at 520 nm originating from the 5d¹4f⁶−4f⁷ transition of Eu²⁺ under 365 nm n-UV excitation. The PL excitation spectrum matches the emission from n-UV chips. These materials could be promising green phosphors for use in generating white light in phosphor-converted white light-emitting-diodes (LEDs).