Investigation of PL properties of C-doped SiO2/Si samples after high energy Pb ion irradiation

Amorphous SiO2 thin films with about 400-500 nm in thickness were thermally grown on single crystalline silicon. These SiO2/Si samples were firstly implanted at room temperature (RT) with 100 keV carbon ions to 2.0 x 10(17),5.0 X 10(17) or 1.2 x 10(18) ions/cm(2), then irradiated at RT by 853 MeV Pb ions to 5.0 x 10(11), 1.0 X.10(12) 2.0 x 10(12) or 5.0 x 10(12) ions/cm(2), respectively. The variation of photoluminescence (PL) properties of these samples was analyzed at RT using a fluorescent spectroscopy. The obtained results showed that Pb-ion irradiations led to significant changes of the PL properties of the carbon ion implanted SiO2 films. For examples, 5.0 x 10(12) Pb-ions/cm(2) irradiation produced huge blue and green light-emitters in 2.0 x 10(17) C-ions/cm(2) implanted samples, which resulted in the appearance of two intense PL peaks at about 2.64 and 2.19 eV. For 5.0 x 10(17) carbon-ions/cm(2) implanted samples, 2.0 x 10(12) Pb-ions/cm(2) irradiation could induce the formation of a strong and wide violet band at about 2.90 eV, whereas 5.0 x 10(12) Pb-ionS/cm(2) irradiation could,create double peaks of light emissions at about 2.23 and 2.83 eV. There is no observable PL peak in the 1.2 x 10(18) carbon-ions/cm(2) implanted samples whether it was irradiated with Pb ions or not. All these results implied that special light emitters could be achieved by using proper ion implantation and irradiation conditions, and it will be very useful for the synthesis of new type Of SiO2-based light-emission materials.

Structural modification of C-doped SiO2 induced by swift heavy ion irradiations

Thermally grown amorphous SiO2 samples were implanted at room temperature (RT) with 120 keV C-ions to a dose ranging from 1.0 x 10(16) to 8.6 x 10(17)C ions/cm(2), then irradiated at RT with 950 MeV Pb, 345 or 1754 MeV Xe ions to a fluence in the region from 1.0 x 10(11) to 3.8 x 10(12) ions/cm(2), respectively. The irradiated samples were investigated using micro-FTIR and micro-Raman spectroscopes. It was found that new chemical bonds such as Si-C, C=C(O), C C and Si(C)-O-C bonds formed significantly in the C-doped SiO2 films after heavy ion irradiations. The evolution of Si-O-C bonds and possible mechanism of structural modification in C-doped SiO2 induced by swift heavy ion irradiations were discussed.

Modification of C-doped a-SiO2 after Swift Heavy-Ion Irradiation

Amorphous SiO2 (a-SiO2) thin films were thermally grown on single-crystalline silicon. These a-SiO2/Si samples were first implanted (C-doped) with 100-keV carbon ion at room temperature (RT) at a dose of 5.0 x 10(17) C-ions/cm(2) and were then irradiated at RT by using 853 MeV Pb ions at closes of 5.0 x 10(11), 1.0 x 10(12), 2.0 x 10(12) and 5.0 x 10(12) Pb-ions/cm(2), respectively. The microstructures and the photoluminescence (PL) properties of these samples induced by Pb ions were investigated using fluorescence spectroscopy and transmission electron microscopy. We found that high-energy Pb-ion irradiation could induce the formation of a new phase and a change in the PL property of C-doped a-SiO2/Si samples. The relationship between the observed phenomena and the ion irradiation parameters is briefly discussed.

Spectroscopic and fluorescence decay behaviors of Yb3+ -doped SiO2-PbO-Na2O-K2O glass

The spectroscopic and fluorescent decay behaviors of Yb3+-doped SiO2-PbO-Na2O-K2O glass is reported in this work. Yb2O3 contents of 1, 1.5 and 2mol% are added into the glass. Through the measurement of absorption and fluorescence spectra, and fluorescent decay rate at room temperature and at low temperature (18 K), it is found that the nonradiative decay rate of Yb3+ ions is mainly determined by the interaction between residual hydroxyl groups and Yb3+ ions. Concentration quenching effect can be omitted in this glass up to the Yb3+ ion concentration of 8.98 x 10(20)/cm(3). Multiphonon decay rate is also very small because of the large energy gap between F-2(5/2) and F-2(7/2) levels of Yb3+ ions. (c) 2004 Elsevier B.V. All rights reserved.

Photoluminesfcence of Er-doped SiO2 films containing Si nanocrystals and Er

Correlations between Si nanocrystal (nc-Si) related photoluminescence (PL), Er3+ emission and nonradiative defects in the Er-doped SiO2 films containing nc-Si (SRSO) are studied. Upon 514.5 nm laser excitation the erbium-doped SRSO samples exhibit PL peaks at around 0.8 and 1.54 mum, which can be assigned to the electron-hole recombination in nc-Si and the intra-4f transition in Er3+, respectively. With increasing Er3+ content in the films, Er3+ emission becomes intense while the PL at 0.8 mum decreases, suggesting a strong coupling of nc-Si and Er 31 ions. Hydrogen plasma treatment for the samples improve the PL intensities of the 0.8 and 1.54 mum bands, indicating H passivation for the nonradiative defects existing in the samples. Further-more, from the effect of hydrogen treatment for the samples, we observe variation of the number of nonradiative defects with annealing temperatures. (C) 2003 Elsevier Science B.V. All rights reserved.

Multiple energy transfers in rare earth complex-doped SiO2 spheres

Silica spheres doped with Eu(TTFA)(3) and/or Sm(TTFA)(3) were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu (TTFA)(3) and Sm(TTFA)(3), namely between the ligand and Eu3+ ion, the ligand and Sm3+ ion, and Sm3+ ion and Eu3+, ion. Energy transfer of Sm3+-> Eu3+, in the hybrid spheres leads to fluorescence enhancement of Eu3+ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.

A novel sensitive solid-state electrochemiluminescence sensor material: Ru(bpy)(2+)(3) doped SiO2@MWNTs coaxial nanocable

A simple, large scale, and one-step process for the preparation of tris(2,2'-bipyridyl)ruthenium(I) (Ru(bpy)(3)(2+)) doped SiO2@carbon nanotubes (MVNTs) coaxial nanocable used for an ultrasensitive electrochemiluminescence (ECL) is presented for the first time. More importantly, a directly coated as-formed functional material on ITO electrode surface exhibits excellent ECL behavior, good stability, and high sensitivity in the presence of tripropylamine (TPA). This novel functional material will find potential applications in biosensor, electrophoresis and electroanalysis.

注碳二氧化硅中高能重离子辐照效应研究

本论文工作采用“低能离子注入+高能重离子辐照”实验方法，通过建立注 碳二氧化硅（SiO2）中结构变化和新结构形成与高能重离子辐照参数的关系，比 较系统地研究了注碳SiO2中高能重离子辐照效应， 并对辐照效应产生机理进行了 初步探讨。 实验中，先将120keV的C离子注入SiO2样品，再用Xe、Pb、U等多种高能 重离子辐照，然后用FTIR、Raman谱和TEM等分析技术对样品进行表征。 实验结果表明， 高能离子辐照注碳非晶SiO2在注碳区形成管状径迹， 在高能 离子引起的离子径迹及其附近区域形成了SiC、 碳团簇、 SiOC结构和CO/CO2分子 并观察到了局域纳米晶化现象，形成的 SiOC 和 SiC 具有链式和笼式结构。新结 构的形成与碳离子注入剂量、高能离子辐照剂量、电子能损以及总沉积能量密度 有关，并存在相应的阈值。根据实验结果并结合热峰模型，我们认为高能重离子 辐照可能在注碳SiO2中引起了一系列化学反应， 其驱动力来自于强电子激发引起 的热峰过程。研究结果还表明，“低能离子注入+高能重离子辐照”是合成具有 特殊功能材料的一种有效手段，通过选择合适的高能重离子辐照，实现有选择结 构相变，可以合成新型功能材料。

Preparation and luminescence properties of Eu2+ in SiO2 xerogels

Al-doped and B, Al co-doped SiO2 xerogels with Eu2+ ions were prepared only by sol-gel reaction in air without reducing heat-treatment or post-doping. The luminescence characteristics and mechanism of europium doping SiO2 xerogels were studied as a function of the concentration of Al, B, the europium concentration and the host composition. The emission spectra of the Al-doped and B, Al codoped samples all show an efficient emission broad band in the blue violet range. The blue emission of the Al-doped sample was centered at 437 nm, whereas the B, Al co-doped xerogel emission maximum shifted to 423 nm and the intensity became weaker. Concentration quenching effect occurred in both the Al-doped and B, Al co-doped samples, which probably is the result of the transfer of the excitation energy from Eu2+ ions to defects. The highest Eu2+ emission intensity was observed for samples with the Si(OC2H5)(4):C2H5OH:H2O molar ratio of 1:2:4. (c) 2006 Elsevier B.V. All rights reserved.