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961.
薛舫时 《固体电子学研究与进展》1995,15(3):228-238
锗硅超晶格和多孔硅的大量实验分析表明,其发光性能既不能用间接带隙来解释,也不同于直接光跃迁。本文通过波函数的谐波分析和表面化学键诱生的能带混合研究得出这两种材料中都可能产生出直接带隙分波,从而得到直接光跃迁。运用这种分波发光模型,解释了锗硅超晶格和多孔硅的大量实验结果。最后比较了这两种材料能带工程中的物理效应和化学效应,提出了综合此两效应优化设计新发光材料的新方法。 相似文献
962.
A. Reiser 《Microelectronics Journal》2009,40(2):306-12268
High-quality, vertically aligned zinc oxide (ZnO) nano-wires were grown by the vapour-transport method on (1 1 2¯ 0) (a-plane) sapphire substrate covered by a uniform ZnO nano-crystalline seed layer which was deposited in a preceding growth step via simple chemical vapour deposition. A thin layer of close-packed nano-seeds with an average size of 12 nm was formed rapidly on the substrate by sublimation and thermal decomposition of zinc acetate dihydrate as the precursor at moderate temperatures and pressures. Subsequently, growth of ZnO nano-wires was performed by a carbo-thermal vapour-transport method yielding nano-wires with high reproducibility and homogeneity. The as-grown, c-axis-oriented nano-wires exhibit excellent luminescence properties and perfect alignment with respect to the substrate surface. 相似文献
963.
Sergei Pyshkin John Ballato Michael Bass Giorgio Turri 《Journal of Electronic Materials》2009,38(5):640-646
The results of luminescence studies conducted on the same samples of GaP over a 40-year period are discussed. The results
strongly imply that periodic ordering of impurities improved the overall optical and mechanical properties of the material
over time. Forty years after preparation, “hot” luminescence spectra in gallium phosphide (GaP) are similar to those for nanocrystals.
The aged pure and N-doped crystals exhibit stimulated emission at 300 K. The aged GaP:N:Sm at room temperature generates bright
green or yellow and red tunable luminescence. These results correlate with Raman light scattering and microhardness data obtained
from the same crystals. 相似文献
964.
Binbin Jiang Lihe Zheng Dapeng Jiang Handi Yin Jiangang Zheng Qiuhong Yang Guofeng Cheng Liangbi Su 《中国稀土学报(英文版)》2021,39(4):390-397
Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF2-SrF2single crystals(3 at%Yb,6 at%RE:CaF2-SrF2)were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF2-SrF2.The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y3+3+3+.The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF2-SrF2and Yb,Gd:CaF2-SrF2,which are larger than 0.85 in Yb,Y:CaF2-SrF2and 0.80 in Yb:CaF2-SrF2.Absorption spectra in the range of 200 and 400 nm were analysed with Yb2+contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF2-SrF2has a relatively higher optical parameter(δem×t,0.52×1020cm2·ms),lower Isat(3.68 kW/cm2)and^min(0.50 kW/cm2)at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF2-SrF2is 302 cm-1which is located between those of CaF2and SrF2as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y3+,Cd3+,La3+)codoped CaF2-SrF2eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers. 相似文献
965.
Boron doped zinc oxide thin films (∼80 nm) were deposited onto pure silica glass by sol-gel dip coating technique from the precursor sol/solution of 4.0 wt.% equivalent oxide content. The boron concentration was varied from 0 to 2 at.% w.r.t. Zn using crystalline boric acid. The nanostructured feature of the films was visualized by FESEM images and the largest cluster size of ZnO was found in 1 at.% boron doped film (B1ZO). The presence of mixed crystal phases with hexagonal as major phase was identified from XRD reflections of the films. Particle size, optical band gap, visible specular reflection, room temperature photoluminescence (PL) emissions (3.24-2.28 eV), infra-red (IR) and Raman active longitudinal optical (LO) phonon vibration were found to be dependent on dopant concentration. For the first time, we report the room temperature fine structured PL emissions as phonon replicas originated from the LO phonon (both IR and Raman active) in 1 at.% boron doped zinc oxide film. 相似文献
966.
Xianmei Xu Yilin WangWenxiu Xia Liya ZhouFuzhong Gong Liangliang Wu 《Materials Chemistry and Physics》2013
Novel water-based core/shell CdTeSe/ZnS quantum dots (QDs) were synthesized by aqueous method. The CdTeSe/ZnS QDs were investigated by high resolution transmission electron microscopy, energy dispersive spectrometry, UV–vis absorption spectra, and photoluminescence spectrum. The as-prepared QDs capped with ZnS shell were spherical in shape with an excellent quantum yield of 16% and emitted bright yellow light. In addition, the CdTeSe/ZnS QDs can be excited by blue or near-UV region, which is an advantage over wavelength converters for white light-emitting diodes (LEDs). White LEDs based on CdTeSe/ZnS QDs, commercially known as Y3Al5O12:Ce3+ (YAG:Ce), and hybrid phosphor of CdTeSe/ZnS QDs and YAG:Ce, were fabricated. The luminescent properties of the resultant white LEDs were evaluated. The higher red-component in the emission spectrum from CdTeSe/ZnS QDs increased the color rendering index (CRI) value of the commercial YAG:Ce-based white LEDs, and the hybrid phosphor-based white LED had CIE-1993 color coordinate, color temperature, and CRI values of (0.3125, 0.2806), 7108 K and 83.3, respectively. 相似文献
967.
In this paper, we report on long- persistence white phosphor SrAl2Si2O8 :Eu2 , Dy3 synthe-sized by the sol - gel method. The luminescent materials prepared by the sol - gel method have many ad-vantages, such as uniform composition, high purity, fine grains and low synthesis temperature. We foundthat SrAl2Si2O8 :Eu2 ,Dy3 phosphor prepared by the sol -gel method can provide more luminescent in-tensity and better afterglow characteristic compared with the same phosphor prepared by solid -statemethod. Namely, the particle size and shape of phosphors should be optimized to obtain the maximumquantum efficiency through energy absorption. The mierostrueture of the phosphor consisted of regularfine grains with an average size of about 0.5. - 1 μm. Under 356 nm light excitation, the broadband emis-sion of the phosphor continues from 350 to 650 ntn and the emission peak is at about 414 nm, which canbe viewed as the typical emission of Eu2 ascribed to the 4f→5d transitions. 相似文献
968.
The size of nanodiamonds formed upon laser irradiation could be easily controlled over simply adjusting laser pulse parameters. The stable size and structure of nanodiamonds were mostly determined by laser power density and pulse width. Both large nanodiamonds with multiply twinning structure (MTS) and small nanodiamonds with single crystalline structure (SCS) emitted strong visible light after surface passivation, and their fluorescence quantum yield (QY) was 4.6% and 7.1%, respectively. 相似文献
969.
Hongbin Liang Zifeng TianHuihong Lin Mubiao XieGuobin Zhang Pieter DorenbosQiang Su 《Optical Materials》2011,33(4):618-622
The spectroscopic properties of Na3Gd(PO4)2 and Na3Gd(PO4)2:Ce3+ phosphors in the VUV-UV spectral range were investigated. Five excitation bands of Ce3+ ions at Gd3+ sites are observed at wavelengths of 205, 246, 260, 292, and 321 nm. Doublet Ce3+ 5d → 4f emission bands are observed at 341 and 365 nm with a decay constant τ1/e around 26 ns. The X-ray excited luminescence of Na3Gd0.99Ce0.01(PO4)2 at room temperature shows a photon yield of ∼17,000 photons/MeV of absorbed X-ray energy. 相似文献
970.
CdTe0.5Se0.5/Cd0.5Zn0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution. 相似文献