Effects of Bi doping on the optical properties of Er:Y2O3

The influences of Bi³⁺ doping on the optical properties of Er³⁺:Y₂O₃ are investigated under UV and IR excitations. The emission intensity of Er³⁺ is remarkably enhanced by the introduction of Bi³⁺ under both two excitations. The emission enhancement under UV excitation originates from the energy transfer from Bi³⁺ to Er³⁺, while under IR excitation it can be attributed to the modification of the local crystal field around the Er³⁺.     

Citric based sol-gel synthesis and luminescence characteristics of CaLa2ZnO5:Euphosphors for blue LED excited white LEDs

A novel class of orange-red phosphors namely CaLa₂ZnO₅ (CLZ) doped with Eu³⁺ ions were prepared by adopting citrate based sol-gel method. Those were thoroughly characterized by means of XRD, SEM, Tg-DTA, photoluminescent (PL) spectral profiles. PL studies reveal that its emission intensity strongly depends on sintering temperature as well as the dopant ion (Eu³⁺) concentration. Eu³⁺ ion doped CaLa₂ZnO₅ phosphor has a strong excitation at 468 nm, which correspond to the popular emission line from a GaN based blue light-emitting diode (LED) chip. The influence of the preparation method on the luminescence property was studied by comparing the emission performance of phosphors prepared by sol-gel and solid-state reaction methods along with a commercial red phosphor Y₂O₂S:Eu³⁺. Thus, the intense red emission (⁵D₀ → ⁷F₂) of the Eu³⁺ doped CLZ phosphors under blue excitation suggests them to be a potential candidate for the production of white light by blue LEDs.     

Nonlinear saturable absorption of the sodium borosilicate glass containing Bi2S3 nanocrystals using Z-scan technique

The sodium borosilicate glass containing Bi₂S₃ nanocrystals is prepared by employing both sol-gel and atmosphere control methods. The third-order nonlinear optical absorption of the glass is investigated in detail using the open-aperture Z-scan technique at the wavelength of 770 nm with a pulse width of 200 fs. The results show that the transformation from saturable absorption to reverse saturable absorption in the glass is observed with the increase of the input light intensity of the laser used. The mechanism of the third-order nonlinear optical absorption is discussed preliminarily in the glass. Meanwhile, XRD, XPS, TEM, (S)TEM, EDAX, HRTEM, and SAED are used to characterize the microstructures of the glass.     

Red-emitting Ln2−xEuxTe2O6:RE (Ln = La, Y; RE = Sm, Gd) phosphors prepared by the Pechini sol-gel method

La_1.90Eu_0.10TeO₆:RE³⁺ (RE = Gd, Sm) and Y₂TeO₆:Eu³⁺nanophosphors were prepared by the Pechini sol-gel process, using lanthanide sesquioxides and telluric acid as precursors. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectra (PL) and fluorescence lifetime were used to characterize the resulting phosphors. The results of XRD indicate that all samples crystallized completely at 1073 K and are isostructural with orthorhombic Ln₂TeO₆. The SEM study reveals that the samples have a strong tendency to form agglomerates with an average size ranging from 40 to 65 nm. The luminescence decay curves suggest for all samples a monoexponential behavior. The photoluminescence intensity and chromaticity were improved for excitation at 395 nm when the co-doping concentration reaches the 1% mol. The optimized phosphorsLa_1.88Eu_0.10Gd_0.02TeO₆and La_1.88Eu_0.10Sm_0.02TeO₆, could be considered an efficient red-emitting phosphor for solid-state lighting devices based on InGaN LEDs.     

Optical properties of antimony-implanted ZnO epilayers

Antimony ions were implanted into ZnO films grown on c-plane sapphire by pulsed-laser deposition. Raman scattering modes of the Sb-implanted samples were found to be influenced by the implantation dose. A characteristic peak at 576 cm^− 1 was observed with an asymmetric shape due to ion damage to the lattice of the implanted ZnO films. When the implant dose was low, the height of the peak was reduced by rapid thermal annealing at 400-600 °C and the symmetry of the spectra was recovered. However, when the Sb dose exceeded 1 × 10¹⁵ cm^− 2, the peak maintained unchanged after rapid thermal annealing at temperatures up to 600 °C. A broad and low Raman peak was observed at 437 cm^− 1, which is related to the surface damage caused by the energetic ion bombarding. Photoluminescence measurement showed a decrease of the bandedge emission at 3.36 eV, a clear effect of defects induced by the implantation, and confirmed partial recovery of the crystal by rapid annealing.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

Characterization of paramagnetic KHo(WO4)2 nanocrystals: Synthesized by polymeric mixed-metal precursor sol-gel method

Nanocrystalline KHo(WO₄)₂ (KHW) particles were successfully synthesized via conventional Pechini sol-gel method. Prepared precursor gel was calcined at 250, 550, 600, 650 and 700 °C, and the resulting samples were analyzed with TG-DTA, powder X-ray diffraction, FT-IR, Raman, FESEM, TEM, UV-Vis-NIR (diffuse reflectance spectrum (DRS)), fluorescence and vibrating sample magnetometer (VSM). Thermal degradation of derived gel was observed up to 400 °C and phase formation starts from 550 °C. The product phase formation at higher annealing temperature was investigated by means of powder XRD. Organic liberation in the samples with respect to temperature was analyzed using FT-IR spectrum. Raman spectrum reveals the formation of tungsten ribbons as well as the quality of the samples while increasing the calcination temperature. The nano size of the synthesized particles was confirmed with FESEM and TEM micrographs. Reflectance and emission studies reveal the corresponding absorption and emission properties of trivalent state holmium ion. Paramagnetic behavior of the derived KHW was confirmed with VSM results.     

溶胶一凝胶法制备掺铝氧化锌薄膜

采用溶胶-凝胶工艺在普通玻璃片上制备了掺铝氧化锌薄膜.通过X-射线衍射(XRD)、原子力显微镜(AFM)对薄膜的组织结构和形貌进行了表征,结果表明:用溶胶-凝胶法制得的掺铝氧化锌薄膜为纤锌矿型结构,呈c轴方向择优生长,表面均匀、致密.通过紫外-可见透射光谱(UV)和标准四探针法对薄膜的光电性能进行了研究.试验发现,当铝离子掺杂浓度为4%(摩尔分数)、溶胶物质的量浓度为0.6mol/L、前处理温度为300℃时,薄膜在可见光区的透过率超过80%,且具有较好的导电性,电阻率为8.0×10-4Ω·cm.     

Band gap and superior refractive index tailoring properties in nanocomposite thin film achieved through sol-gel co-deposition method

Transparent nanocomposite ZrO₂-SnO₂ thin films with molar ratio 0.1/0.9 (ZS19), 0.3/0.7 (ZS37), 0.5/0.5 (ZS55), 0.7/0.3 (ZS73) and 0.9/0.1 (ZS91) of ZrO₂/SnO₂ were prepared by sol-gel dip-coating technique. X-ray diffraction (XRD) spectra showed a mixture of three phases: tetragonal ZrO₂ and SnO₂ and orthorhombic ZrSnO₄. X-ray photoelectron spectroscopy (XPS) gives Zr 3d, Sn 3d and O1s spectra on ZS55 thin film which revealed the presence of oxygen vacancies in the nanocomposite ZrO₂-SnO₂ thin film. Scanning electron microscopy (SEM) observations showed that microstructure of ZS55 consists of uniformly dispersed isolated SnO₂ particles in ZrO₂ matrix. An average transmittance greater than 85% (in UV-visible region) is observed in the films ZS55, ZS73 and ZS91, but superior optical properties was observed in ZS55 thin film. The composite system under certain compositional mixings (ZS55) displayed a refractive index supremacy over pure zirconia films which can be directly employed in extending the range of tunability of the refractive index. Besides, these films also demonstrated tailoring of band gap values. Photoluminescence (PL) spectra revealed an intense emission peak at 424 nm in ZS55 sample which indicates the presence of oxygen vacancies in ZrSnO₄. All these characterizations distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present ZrO₂-SnO₂ co-deposited composites.     

Conductive and transparent Bi-doped ZnO thin films prepared by rf magnetron sputtering

Bi-doped ZnO thin films were grown on glass substrates by ratio frequency (rf) magnetron sputtering technique and followed by annealing at 400 °C for 4 h in vacuum (~ 10^− 1 Pa). The effect of argon pressure on the structural, optical, and electrical properties of the Bi-doped films were investigated. The XRD patterns show that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. Some excellent properties, such as high transmittance (about 85%) in visible region, low resistivity value of 1.89 × 10^− 3 W cm and high carrier density of 3.45 × 10²⁰ cm^− 3 were obtained for the film deposited at the argon pressure of 2.0 Pa. The optical band gap of the films was found to increase from 3.08 to 3.29 eV as deposition pressure increased from 1 to 3 Pa. The effects of post-annealing treatments had been considered. In spite of its low conductivity comparing with other TCOs, Bi-doping didn't appreciably affect the optical transparency in the visible range of ZnO thin films.     

Catalyst-free synthesis, growth mechanism and optical properties of multipod ZnO with nanonail-like legs

Multipod ZnO with nanonail-like legs was synthesized successfully by a facile combustion oxidation method at 880 °C without any catalysts. The morphologies of three samples obtained from three growth stages, namely sprout, growing and multipod with nanonail-like legs, were investigated. The possible growth mechanism was discussed in detail. Compared with the other two structures, the multipod with nanonail-like legs exhibited a significant enhancement in the green emission region. Its unique structure together with its good optical properties suggest that it is a promising candidate for the fabrication of optical nanodevices.     

Preliminary Study on Electrical and Optical Properties of ZnO Film Grown by MOCVD

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