0000000000144370
AUTHOR
V. Laguta
Electron Spin Resonance study of charge trapping in α-ZnMoO4 single crystal scintillator
The origin and properties of electron and hole traps simultaneously appearing in a-ZnMoO4 scintillator after X-ray irradiation at low temperatures (T < 35 K) were studied by Electron Spin Resonance (ESR). ESR spectrum of the electron type trap shows pronounced superhyperfine structure due to the interaction of electron spin with nuclear magnetic moments of 95,97Mo and 67Zn lattice nuclei. Considering the nearly tetragonal symmetry of the center this allows us to identify the electron trap as an electron self-trapped at the (Mo(1)O4) 2 complex. Nearly 60% reduction of the spin–orbit coupling at the Mo(1) ion is caused by the overlap of the Mo and ligand oxygen orbitals indicating an essentia…
Study of the defects in La3Ta0.5Ga5.5O14 single crystals
Abstract Defects that are formed during crystal growth pose a serious obstacle for potential application of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) as a laser or piezoelectric crystal. We have performed the study of the defects origin in LGT crystals grown in different atmospheres using optical, EPR and time-resolved luminescence characterization methods. The absorption bands detected in the transparency region at 290, 360 and 490 nm ( T =300 K) demonstrate different dependence on crystal annealing in vacuum and air. EPR analysis demonstrated that the defects responsible for these bands are non-paramagnetic. X-ray irradiation results in hole trapping by oxygen ions thus forming O − centers perturbed …
Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films
The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb3+, Tm3+, Sm3+, and Ho3+ ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr3+ and Fe3+ impurities. The samples 5 × 5 mm2 were positioned in the classical straws and within an estimated accuracy of 10−6 emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can b…
Eu2+ Stabilization in YAG Structure: Optical and Electron Paramagnetic Resonance Study
A set of Eu-doped Y3Al5O12 (YAG) phosphors in the powder form was successfully synthesized by multiple-step solid-state reaction under the reducing Ar:5%H2 atmosphere. Their physical properties were investigated by means of X-ray diffraction, time-resolved luminescence spectroscopy, and electron paramagnetic resonance (EPR). Special attention was given to well-grounded confirmation of Eu2+ occurrence in the YAG structure. X-ray diffraction confirmed the presence of a major YAG phase in all samples. The influence of Eu concentration, form of doping (EuS, EuF2, or Eu2O3) and number/form of annealing steps was studied. Corresponding characteristics were measured and evaluated in a broad temper…
EPR study of Ce3+ luminescent centers in the Y2SiO5 single crystalline films
Abstract The work reports results of EPR investigation of the Ce3+ incorporation in the Y2SiO5 and (Y,La)2SiO5 single crystalline films (SCFs), grown by liquid phase epitaxy method. The Ce3+ content determined from EPR spectra varied between 0.49 and 0.65 at. % in Y2SiO5 SCFs and strongly increased up to 1.9 at. % in (Y,La)2SiO5 SCF, suggesting a positive role of the La dopant in the incorporation of the Ce3+ ions into Y2SiO5 host. The EPR study showed the presence of only one type of Ce3+ centers (Ce1) corresponding to the localization of Ce3+ ions in the seven–fold coordinated positions of the Y2SiO5 host. No Ce2 center spectra (six-fold coordinated Ce3+ positions) were detected in films …
Tunable Eu2+ emission in KxNa1 − xLuS2 phosphors for white LED application
Set of Eu2+-doped KxNa1 − xLuS2 phosphors (x = 0–1) in the form of transparent crystalline hexagonal platelets was successfully synthesized by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, X-ray fluorescence, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Special attention was given to photoluminescence emission spectra under the 395 nm and 455 nm excitation aiming to obtain white emission with tunable color temperature. EPR method was employed to understand the Eu2+ incorporation and distribution in the KxNa1 − xLuS2 hosts. CIE xy-coordinates were calculated to compare effects o…
LPE growth and study of the Ce3+ incorporation in LuAlO3:Ce single crystalline film scintillators
This work reports the results of the optical and electron paramagnetic resonance (EPR) investigation of the Ce3+ incorporation in single crystalline film (SCF) scintillators of Ce-doped LuAlO3 perovskite, grown by the liquid phase epitaxy method onto YAlO3 substrates using a PbO–B2O3 flux. The absorption, luminescence and EPR spectra showed the presence of the main Ce3+ center type (CeLu) corresponding to the location of Ce3+ ions in the twelve-fold coordinated cuboctahedral positions of the LuAlO3 host. Also the dimer CeLu–CeLu centers were found in the EPR spectra of the LuAP:Ce SCFs. No EPR spectrum of the Ce3+ ions located in the octahedral positions of Al3+ cations has been detected in…