Structural and optical properties of Er2O3 films

Stoichiometric and amorphous Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er2O3 film in wavelength region of 400-1000 nm was between 1.6-1.7. The reflectivity of the Er2O3 films decreased greatly with respect to that from the uncoated Si substrates. The absorption coefficient of the Er2O3 film indicated that it had an energy gap larger than 4.5 eV. The obtained characteristics indicated...     

Incorporation of Si-Ninducing white light of SrAl_2Si_2O_8：Eu~（2＋）,Mn~（2＋） phosphor for white light emitting diodes

Photoluminescence (PL) and colorimetric properties of white-light emission SrAl2Si2O8:Eu2+,Mn2+ phosphor were tuned effectively through incorporating Si-N bond to the host in the form of Si3N4. A maximum solubility of Si-N bond in SrAl2-xSi2+xO8-xNx was estimated theoretically to be in a value of x=1.0. Under 365 nm irradiation, a distinct red-shift of blue band emission from 406 to 473 nm for Eu2+ and an enhancement of yellow band emission peaked at ~565 nm for Mn2+ were observed with the increase of Si-N ...     

In situ photoemission study of interface and film formation during epitaxial growth of Er_2O_3 film on Si(001) substrate

Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si(001) interface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maxi-mum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.     

Band offsets between amorphous LaeHf2O7 and silicon

Amorphous La2Hf2O7 films were grown on Si(100) by pulsed laser deposition method. The valence and conduction band offsets between amorphous La2Hf2O7 film and silicon were determined by using synchrotron radiation photoemission spectroscopy. The energy band gap of amorphous La2Hf2O7 film was measured from the energy-loss spectra of O 1s photoelectrons. The band gap of amorphous La2Hf2O7 film was determined to be 5.4±0.2 eV. The valence and the conduction-band offsets of amorphous La2Hf2O7 film to Si were obtained to be 2.7±0.2 and 1.6±0.2 eV, respectively. These results indicated that the amorphous La2Hf2O7 film could be one promising candidate for high-k gate dielectrics.     

Erbium photoluminescence response related to nanoscale heterogeneities in sol-gel silicates

Sol-gel glassy films of the SiO2-TiO2-PO2.5-ErO2.5 system containing nanocrystallites of ErPO4, were obtained through suitable heat treatments. Variations in the shape and intensity of the Er3+ photoluminescent signal around 1500 nm were linked to the nature of the host environment of the active ions; the specific features of the photoluminescent emission spectrum of the erbium 4I13/2 metastable level were interpreted in terms of structural changes in the glassy films. The photoluminescent spectrum was found to be sensitive to the order (crystalline) or disorder (amorphous) of the Er3+ ions neighbour within the glassy matrix. An amorphous environment led to a broadening of Er3+ PL emission band while a crystalline one was responsible for a drastic photoluminescent bandwidth narrowing. The presence of nanoscale heterogeneities caused a drastic photoluminescence intensity decrease. Changes in the shape of the decay curve of fluorescence lifetime were found also structurally dependent on volumetric defects, occurrence of phase separation and Er3+-Er3+ clustering effects as well.     

Photoluminescence Characteristics of Gd2Mo3O9 ： Eu Phosphor Particles by Solid State Reaction Method

Eu^3＋-doped Gd2Mo3O9 was prepared by solid-state reaction method using Na2CO3 as flux and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belonged to a tetragonal system with space group I41/α. The effects of flux content and sintering temperature on the luminescent properties were investigated with the emission and excitation spectra. The results showed that flux content and sintering temperature had effects on the luminescent properties, the optimized flux content and the best temperature was 3 % and 800 ℃ respectively. The excitation and emission spectra also showed that this phosphor could be effectively excited by C-T band （280 nm）, ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 and 465 nm were nicely fitting in with the widely applied output wavelengths of ultraviolet or blue LED chips. Integrated emission intensity of Gd2Mo3O9 ： Eu was twice higher than that of Y2O2S ： Eu^3 ＋ under 395 nm excitation. The Eu^3＋ doped Gd2Mo309 phosphor may be a better candidate in solid-state lighting applications.     

Rare earth （Eu2＋,ce3＋） activated BaAIESi2O8 blue emitting phosphor

Blue emitting rare earth（Eu2＋,Ce3＋） doped BaAl2Si2O8 phosphors were synthesized by combustion methods at 600 oC. BaAl2Si2O8： Eu2＋ phosphor showed isolated broad blue emission band at 455 nm, when it was excited with the wavelength of 329 nm. Whereas BaAl2Si2O8：Ce3＋ phosphor exhibited blue emission band at 442 nm, under 303 nm excitation wavelength. These observed emission bands of Eu2＋ and Ce3＋ ions corresponded to 5d-4f allowed transitions. The position of emission band was calculated by using the equationE=Q[1-〔V/4〕^1/V）]× 10 （nEar/80）Also the spin orbit splitting difference in the ground state levels of Ce3＋ ion was studied by Gaussian curve fitting. Broad absorption and emission bands in blue regions made prepared phosphors a promising blue host for the white-LEDs.     

Band gap and structure characterization of Tm2O3 films

Single crystalline Tm2O3 films were grown on Si (001) substrates by molecular beam epitaxy using metallic Tm source and atomic oxygen source. X-ray photoelectron spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy were employed to investigate the compositions, surface morphology and microstructure of the sample. A very flat surface with a root mean square roughness of 0.3 nm could be reached, and a sharp interface between the film and the Si substrate was achieved. The result of optical spectrum at ultraviolet and visible wavelengths showed that the band gap of the Tm2O3 film was 5.76 eV.     

Synthesis and luminescence properties of bluish-green emitting K2MgSi3O8:Eu2+ phosphor

Eu2+-doped K2 Mg Si3O8 phosphors were synthesized by conventional solid-state reaction method. The phase formation of as-prepared samples was characterized by X-ray powder diffraction. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve and CIE coordinates. The phosphor showed bluish-green emission centered at 460 nm under the excitation of UV and near UV light with the wavelength range of 250–430 nm. Two Eu2+ emission centers existed in the K2 Mg Si3O8:Eu2+ phosphor according to the luminescence spectra and the decay curves. The critical quenching concentration of Eu2+ doping was determined to be 3.0 mol.% and the concentration quenching mechanism was dipole-dipole interactions between Eu2+ ions. These results suggested that K2 Mg Si3O8:Eu2+ was a potential bluish-green phosphor candidate for white UV-LED.     

Origin of light emission and enhanced Eu3+photoluminescence in tin-containing glass

A barium-phosphate glass matrix was co-doped with Sn O and Eu2O3 for investigating on material luminescent properties. Optical absorption and X-ray photoelectron spectroscopy(XPS) were employed in the characterization of tin species. The prevalence of divalent tin was indicated by the XPS data in accord with a conspicuous absorption band detected around 285 nm ascribed to twofold-coordinated Sn centers(isoelectronic with Sn2+). Photoluminescence(PL) excitation spectra obtained by monitoring Eu3+ emission from the 5D0 state revealed a broad excitation band from about 250 to 340 nm, characteristic of donor/acceptor energy transfer. Under excitation of such at 290 nm, the co-doped material exhibited a bright whitish luminescence, and a four-fold enhanced Eu3+ emission relative to a purely Eu-doped reference. Time-resolved PL spectra recorded under the excitation at 290 nm exposed a broad band characteristic of the twofold-coordinated Sn centers and emission bands of Eu3+ ions, which appeared well separated in time in accord with their emission decay dynamics. The data suggested that light absorption took place at the Sn centers(donors) followed by energy transfer to Eu3+ ions(acceptors) which resulted in populating the 5D0 emitting state. Energy transfer pathways likely resulting in the enhanced Eu3+ photoluminescence and the consequential light emission were discussed.     

Shape-Controlled Synthesis and Upconversion Luminescence of Y2O3:Yb, Er Microstructures

The Y2O3: Yb3 , Er3 microstructures were fabricated by a hydrothermal method without surfactants.The microstructures structure was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM,KYKY 1000B).The up-conversion luminescence spectra were studied under 978 nm laser diode excitation.In Yb3 and Er3 codoped Y2 O3 microcrystals, the relative intensity of green emission became stronger as the morphology of sample changed from wires to films.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Local microstructure and photoluminescence of Er-doped 12CaO·7Al2O3 powder

Er-doped 12CaO·7Al2O3 (C12A7:Er) powders were prepared using the sol-gel method followed by annealing inorganic precursors. X-ray diffraction (XRD), Raman and absorption spectra revealed that Er ions existed and substituted Ca2 lattice site in C12A7. The photoluminescence of C12A7:Er at room temperature was observed in the visible and infrared region using 488 nm (2.54 eV) Ar line as excitation source, respectively. The sharp and intense green emission bands with multi-peaks around 520 nm and 550 nm correspond to the transitions from the excited states 2H11/2 and 4S3/2 to the ground state 4I15/2, respectively. Furthermore, red emission band around 650 nm was also observed. It was attributed to the electronic transition from excited states 4F9/2 to the ground state 4I15/2 inside 4f-shell of Er3 ions. The intensive infrared emission at 1.54μm was attributed to the transition from the first excited states of 4I13/2 to the ground state (4I15/2). The temperature dependent photoluminescence of infrared emission showed that the integrated intensity reached a maximum value at near room temperature. The forbidden transitions of intra-4f shell electrons in free Er3 ions were allowed in C12A7 owing to lack of the inversion symmetry in the Er3 position in C12A7 crystal field. Our results suggested that C12A7:Er was a candidate for applications in Er-doped laser materials, and full color display.     

Luminescence of Er3+ Doped Titanium Barium Glass Microsphere under 514 nm Excitation

The titanium barium glass microspheres doped with Er2O3 were designed and prepared. The components of the glass sample were 25TiO2-27BaCO3-8Ba(NO3)2-5ZnO2-10CaCO3-5H3BO3-10SiO2-7water glass-3Er2O3 (%, mass fraction). The emission spectra of titanium barium glass matrix and the titanium barium glass microsphere under 514 nm excitation were measured with micro-Raman spectrometer. Whispering gallery modes in the emission spectra from a 31 μm glass microsphere were observed. Many regularly spaced, sharp peaks appeared in the emission spectra of the Er2O3-doped glass microsphere. The wavelength separation between the two adjacent peaks is 1.92 nm for the 31 μm microsphere. According to the Lorenz-Mie formula, the calculated value of the wavelength separation between the two adjacent peaks is 1.95 nm. The observed resonances could be assigned by using the well-known Lorenz-Mie formula.     

Structure Property and Visible Upconversion of Er^3＋ Doped Gd2O3 Nanocrystals

Gd2O3:Er nanoparticles were prepared by a simple sol-gel method, The structure properties ot Gd2O3:Er were studied by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. The visible up-converted luminescence spectra of Er^3 were investigated under excitation to ^4I9/2 level by 785nm laser. Laser power, Er^3 ion concentration and temperature dependences of the upconverted emissions were investigated to understand the upconversion mechanisms. Excited state absorption and energy transfer process are discussed as the possible mechanisms for the upconversion.     

Upconversion properties of Y2O3：Er films prepared by sol-gel method

Y2O3:Er3+ films were prepared by a simple sol-gel process. The structural properties of Y2O3:Er3+ flints were characterized with X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The results indicated that the Y2O3:Er3+ f'rims might have high upconversion efficiency because of their low vibrational energy. Under 785 and 980 nm laser excitation, the samples showed green (2H11/2→4I15/2, 4S3/2→4I15/2) and red (4F9/2→4I15/2) upconversion emissions. The upconversion mechanisms were stud-led in detail through laser power dependence. Excited state absorption and energy transfer process were discussed as possible upconversion mechanisms. The cross relaxation process in Er3+ was also investigated.