W.X. Que

Influence of annealing atmosphere and temperature on photoluminescence of Tb3+ or Eu3+-activated zinc silicate thin film phosphors via sol–gel method

Abstract Thin films of Zn 2 SiO 4 :Tb 3+ or Eu 3+ were deposited on silicon wafers by a sol–gel method. The films exhibited prominent green or red photoluminescence, due to the sharp and strong intra-4f n -shell electronic transitions. The thermogravimetric analysis curve shows a remarkable weight loss in the temperature range 50–400 ° C , and a slow loss at higher temperature. The increases in fluorescence intensity and decay lifetimes of rare-earth ions sensitive to microstructure and chemical components are attributed to OH removal, nano-crystallite formation and the increased surface roughness by treatment of temperature. Strongly enhanced photoluminescence was observed in samples annealed at 950 °C in a nitrogen atmosphere.

Luminescence of Eu3+ and Tb3+ doped Zn2SiO4 nanometer powder phosphors

Abstract We report, for the first time to the best of our knowledge, the luminescent properties of Tb 3+ and Eu 3+ doped Zn 2 SiO 4 phosphors prepared by a sol–gel process. The phosphors have shown prominent luminescence in green and red, respectively, due to the electronic transitions of 5 D 0 → 7 F 2 (Eu 3+ ) and 5 D 4 → 7 F 5 (Tb 3+ ). Structural characterization of these luminescent materials was carried out with XRD and TEM. Luminescence spectra were analyzed by measuring the excitation, photoluminescence spectra and lifetimes of the emission transitions of Eu 3+ ( 5 D 0 → 7 F J , J =1–5) and Tb 3+ ( 5 D 4 → 7 F J , J =1–6). Our experimental results have shown that these phosphors have comparable luminescence properties as those currently used in TVs and CRTs.

Effects of composition and structure on spectral properties of Eu3+-doped yttrium silicate transparent nanocrystalline films by metallorganic decomposition method

Abstract Transparent thin films of (Eu x Y 1− x ) 2 SiO 5 and (Eu x Y 1− x ) 2 Si 2 O 7 ( x =0.005∼0.05) have been prepared using a metallorganic decomposition sol–gel process. A strong room temperature red emission with predominant wavelength at 614 nm, corresponding to the 5 D 0 → 7 F 2 intra-4f n electric transition of Eu 3+ , has been observed as a function of the annealing temperature. Correlations were observed between optical properties and film structures. As a consequence, a great change in luminescence and CIE coordinates of Eu 3+ -doped Y 2 SiO 5 at high temperature around 1050 °C was attributed to phase transformation of nanocrystalline films. Upon exposure to the UV source, these thin films have shown bright red-phosphorescent color with excellent color saturation.

Sol–gel derived nanocrystalline thin films of PbTiO3 on glass substrate

Thin films of PbTiO3 have been prepared on soda-lime glass substrates. The sol was prepared by mixing tetrapropyl orthotitanate and lead acetate trihydrate in acetic acid. The films were deposited by spin coating and annealed at 500°C for 30 min. The structural and optical properties of the films were characterized by means of X-ray diffraction, atomic force microscopy, variable angle spectroscopic ellipsometry, UV-VIS spectroscopy, micro-Raman spectroscopy and the m-line technique. The electrical properties of the film were studied with a Sawyer–Tower bridge. The films have a pure perovskite phase with a c/a ratio of 1.054 and consist of crystallites with a size of a few tens of nanometers. Raman studies show the typical phonon modes of PbTiO3, and the shift of the Raman peaks indicates that the films are stressed. The films are highly transparent and the absorption edge is approximately 3.70 eV. A two-layer film is found to support two TE and two TM modes at a wavelength of 633 nm.

C-axis oriented sol–gel derived LiNb1−xTaxO3 thin films on Si(111) substrates

Abstract We have successfully prepared highly c -axis oriented sol–gel derived LiNb 1− x Ta x O 3 films on Si(111) substrates. The orientations of LiNb 1− x Ta x O 3 films for different values of the tantalum composition, x , are investigated . Highly c -axis oriented films were obtained in the composition range of 0 x x c -axis orientation of the films is believed to result from a weak effect caused by the 3-fold symmetry match between the film and the Si(111) substrate. C -axis oriented LiNb 1− x Ta x O 3 films are very useful in integrated optical devices, pyroelectric devices, and metal-ferroelectric-semiconductor non-volatile memory applications.

LiTaO3 films with c-axis preferred orientation prepared on Si(111) substrate by sol-gel method

LiTaO3 films with c-axis preferred orientation have been prepared on Si(111) substrates using sol–gel spin-coating and rapid thermal annealing. Hydrogen-terminated silicon surface, preheating temperature, and unidirectional heat flow during the heat treatment are essential factors for the c-axis texture. The texture is useful in pyroelectric, metal-ferroelectric-semiconductor (MFS) nonvolatile memory, and integrated optics applications.

An efficient lasing action from pyrromethene 556 dye-doped organically modified silicates

Abstract Organically modified solid-state silicates (ORMOSILS) doped with a new laser dye 1,3,5,7,8-pentamethylpyrromethene-2,6-disulfonate–BF 2 complex (pyrromethene 556) have been synthesized by a sol–gel method and the compositional effects on pore characteristics, fluorescence and lasing properties have been investigated. It is found that the use of dimethylsulfoxide and γ-glycidoxypropyltrimethoxysilane could greatly change the structure properties of sol–gel derived ORMOSILS cage, and thus the fluorescence and lasing properties of the materials could improve significantly. A successful laser oscillation from this dye-doped ORMOSILS sample has been achieved upon pumping with a Q-switched frequency-doubled Nd:YAG laser at 532xa0nm. A slope efficiency of 54% with a useful lifetime greater than 10,000 shots has been demonstrated at a pump repetition rate of 1xa0Hz and a pump intensity of 1xa0J/cm 2 by using the new ORMOSILS cage on our newly designed laser system. Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a compact new laser device by low cost dye-doped solid-state ORMOSILS.

Preparation and characterization of erbium oxalate and erbium oxide nanoparticles by microemulsion technique

Abstract This paper reports the preparation and characterization of erbium oxalate and erbium oxide nanoparticles. The erbium oxalate and erbium oxide phosphor materials were synthesized through the microemulsion technique. Transmission electron microscopy (TEM) was used to characterize the phosphor materials and reveal a nanocrystal structure for the studied phosphors. A strong green up-conversion emission at 543 nm ( 4 S 3/2 → 4 I 15/2 ) and another weak emission at 528 nm ( 2 H 11/2 → 4 I 15/2 ) have been measured for the studied phosphors upon excitation at 993 nm ( 4 I 11/2 → 4 I 15/2 ). The up-conversion emission mechanism has been explained by means of an energy level diagram. The lifetimes of these emissions have been measured. The green up-conversion emission equally strong in both the phosphors and for these phosphors, color coordinates ( X , Y ) have been obtained in order to assess their color emitting efficiency.

Photoluminescence of erbium oxide nanocrystals/TiO2/γ-glycidoxypropyltrimethoxysilane (GLYMO) composite sol–gel thin films derived at low temperature

Erbium (III) oxide nanocrystals prepared using the inverse microemulsion technique were dispersed in sol–gel TiO2/γ-glycidoxypropyltrimethoxysilane (GLYMO) composite thin films at low temperature. X-ray diffraction analysis and transmission electron microscopy observation show that the erbium (III) oxide nanoparticles have a nanocrystalline structure and their size is in the range from 5 to 30 nm. A relatively strong room-temperature photoluminescence (PL) was observed at 1.531 μm with a full width at half-maximum (FWHM) of 22 nm. The shape, peak position, and FWHM of the PL curve from the composite thin films are quite comparable to those prepared by other methods. The PL peak of the composite thin film reached a maximum intensity after a heat treatment at 300u200a°C. Fourier transform infrared results show that water and hydroxyl groups are present in the films and are responsible for the luminescence peak intensity reduction of the films heated at higher temperature.