高能Xe离子辐照引起的注碳a:SiO_2中新结构的形成

先用120 keV的碳离子注入非晶二氧化硅a:SiO2薄膜,再用能量为1 754 MeV的Xe离子辐照。注碳量为5.0×1016—8.6×1017ion/cm2,Xe离子辐照剂量为1.0×1011和5.0×1011ion/cm2。辐照后的样品中形成的新结构用显微傅立叶变换红外光谱仪进行测试分析。结果表明,Xe离子辐照引起了注碳a:SiO2中Si—C,C—C,Si—O—C键以及CO和CO2分子的形成与演化。在注碳量较高时,Xe离子辐照在样品中产生了大量的Si—C键。与注入未辐照和辐照的低注碳量样品比较,增强的Si—C键的形成,预示着辐照可引起注碳a:SiO2样品中的SiC结构相变。

高能Pb离子辐照注碳SiO_2的红外谱研究

室温下,先用120keV的C离子注入二氧化硅薄膜样品至剂量2.0×1017,5.0×1017或8.6×1017ions/cm2,再用950MeV的Pb离子分别辐照至剂量5.0×1011,1.0×1012或3.8×1012ions/cm2,然后测量样品的傅里叶变换红外(FTIR)光谱.通过分析测量得到的傅里叶变换红外谱,发现Pb离子辐照在注碳SiO2样品中可引起大量的Si—C和Si(C)—O—C等化学键的形成,大剂量Pb离子辐照可在大剂量注碳的SiO2中产生分子CO2.大量的Si—C键的存在和分子CO2的形成,预示着高能Pb离子辐照在注碳SiO2样品中有可能形成了纳米Si团簇和/或SiC晶粒.

离子辐照对单晶Si中预注入B原子扩散的影响

室温下使用MeV能量级Si,F和O离子对 5keVB离子预注入后的n -型单晶Si( 1 0 0 )进行了辐照 ,应用二次离子质谱仪测试分析了掺杂物B原子的分布剖面及其变化 .结果表明 ,高剂量Si,F和O离子的附加辐照可以抑制热激活退火中B原子发生的瞬间增强扩散 .在相同的辐照条件下 ,Si近表面区域中SiO2层的存在更有助于限制B原子的瞬间增强扩散 .结合卢瑟福沟道背散射分析和DICADA程序计算对实验结果进行了讨论

V5+-doped Bi3.4Yb0.6Ti3O12 fatigue resistant ferroelectric thin films

In this paper, a serial of Bi3.4Yb0.6Ti3-xVxO12 (BYTV) thin film with different V5+ contents were deposited on Pt/Ti/SiO2/Si substrates by chemical solution deposition (CSD). The crystallized phase and electrical properties of the films were investigated using X-ray diffraction, polarization hysteresis loops, leakage current-voltage, and fatigue test. From our experimental results, it can be found that the ferroelectric properties can be improved greatly using V5+-doped in Bi3.4Yb0.6Ti3O12 (BYT) thin film, compared with the reported BYT thin film. The remanent polarization was enhanced and excellent leakage current characteristic with 10(-11)A at the bias voltage of 4V, which is much lower than the BYT thin film or some reported bismuth layer-structure ferroelectric films. Fatigue test shows that the fabricated films have good anti-fatigue characteristic after 10(10) switching cycles. (c) 2008 Published by Elsevier B.V.

Effects of helium and oxygen common implantation in silicon wafer

Defect engineering for SiO2] precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (STMOX). Cavities are created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120keV 8.0 x 10(16) cm(-2) O ions. The O ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectional transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.

Slow highly charged ion O4+ induced electron emission from clean solid surfaces

The. total electron emission yields following the interaction of slow highly charged ions (SHCI) O4+ with different material surfaces (W, Au, Si and SiO2) have been measured. It is found that the electron emission yield gamma increases proportionally with the projectile velocity v ranging from 5.36 x 10(5)m/s to 10.7 x 10(5)m/s. The total emission yield is dependent on the target materials, and it turns out to follow the relationship gamma(Au) > gamma(Si)> gamma(W). The result shows that the electron emission yields are mainly determined by the electron stopping power of the target when the projectile potential energy is taken as a constant, which is in good agreement with the former studies

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV Fe-56 and 1.755 GeV Xe-136 ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

高电荷态离子与固体表面作用的离子溅射和电子发射的实验研究

高电荷态离子与固体表面相互作用的研究是目前国际上广受关注的热点研究领域之一。本论文详细介绍了在兰州重离子加速器国家实验室ECR离子源上建成的高电荷态离子表面物理实验平台；着重叙述了在实验平台上完成的高电荷态离子在固体表面引起的离子溅射和电子发射的研究。我们用初动能Ek=216～720keV的高电荷态Pb36+离子和初动能为Ek=144～288keV的Arq+（q =11～16）离子以不同入射角度(Ψ＝15º～80º)作用于Nb、Si和SiO2表面，通过研究离子溅射产额与入射离子初动能、势能（电荷态）和入射角度的关系，得到了以下结论：离子溅射产额与炮弹离子的势能沉积和动能作用有关；对Ar离子，电荷态从11增加到16时，离子溅射产额是随之增长的。而对Pb36＋离子，表面离子溅射产额随入射离子初动能的变化关系跟核阻止能损随入射离子初动能的变化关系是一致的，离子溅射产额与核阻止能损是线性相关的。认为高电荷态引发的表面离子溅射过程是势能沉积作用与线性级联碰撞过程协同作用的结果。我们还测量了Heq+(q=1,2, Ek=12keV～48keV)，Neq+(q=2～8, Ek=18～192keV)，Arq+(q=3～12, Ek=72keV)离子垂直作用于Si, W, Au表面产生的电子发射产额。得到了纯粹势能电子发射产额与入射离子势能的定量关系，势能电子产额随入射离子势能的增加而线性增加，势能每增加1eV，单离子电子发射产额增加0.0088（以初动能为42keV的Neq+入射到W表面为例）。势能电子发射增量跟靶的性质有关，W表面对势能变化的响应最剧烈，其次是Si表面。通过引入纯粹动能电子产额与电子能损的比值B分析和研究了动能电子发射，随着入射离子原子序数和初动能的增加，B因子有缓慢降低的趋势；B因子与靶材料密切相关，Au靶的B因子明显大于Si靶和W靶；我们还首次把B因子的研究扩展到高电荷态离子领域，认为B因子与入射离子的势能（电荷态）无关

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。

Liquid-phase hydrodechlorination of chlorinated benzenes over active carbon supported nickel catalysts under mild conditions

Liquid phase hydrodechlorination of chlorinated benzenes was studied over Ni/active carbon (Ni/AC), Ni/gamma-Al2O3, Ni/SiO2 and Raney Ni. The complete dechlorination of chlorobenzene (ClBz) was realized at 333-343 K on Ni/AC under hydrogen atmosphere of 1.0 MPa in the presence of alkaline hydroxide. Dichloro- and trichlorobenzenes were also hydrodechlorinated with 50-95% yields of benzene under the similar conditions, as above. The reaction follows zero-order to ClBz concentration and 1.9 order to hydrogen pressure. The reaction does not proceed in the absence of alkaline hydroxide, suggesting the complete coverage of active nickel surface with produced chlorine and the removal of the chlorine ion with hydroxide ion as a rate-limiting step. The active catalysts were characterized by H-2 chemisorption and transmission electron microscopy techniques. The apparent activity strongly depends on the active area of nickel on catalyst surface. (C) 2004 Published by Elsevier B.V.

Effect of support on chromium based catalysts for the oxidative dehydrogenation of C2H6 with CO2 to C2H4

The oxidative dehydrogenation of ethane (ODE) with CO2 to C2H4 has been studied over a series of Cr-based catalysts using SiO2, Al2O3, (MCM-41 zeolite) MCM-41, MgO and Silicate-2 (Si-2) as the supports. TPR, NH3-TPD, and EPR characterizations of catalysts were carried out to investigate the reduction property of Cr species on different supports, the acidities of catalysts and Cr species of 6Cr/SiO2 catalysts, respectively.

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Isolated transition metal ions/oxides in molecular sieves and on surfaces are a class of active sites for selective oxidation of hydrocarbons. Identifying the active sites and their coordination structure is vital to understanding their essential role played in catalysis and designing and synthesizing more active and selective catalysts. The isolated transition metal ions in the framework of molecular sieves (e.g., TS-1, Fe-ZSM-5, and V-MCM-41) or on the surface of oxides (e.g., MoO3/Al2O3 and TiO2/SiO2) were successfully identified by UV resonance Raman spectroscopy. The charge transfer transitions between the transition metal ions and the oxygen anions are excited by a UV laser and consequently the UV resonance Raman effect greatly enhances the Raman signals of the isolated transition metal ions. The local coordination of these ions in the rigid framework of molecular sieves or in the relatively flexible structure on the surface can also be differentiated by the shifts of the resonance Raman bands. The relative concentration of the isolated transition metal ion/oxides could be estimated by the intensity ratio of Raman bands. This study demonstrates that the UV resonance Raman spectroscopy is a general technique that can be widely applied to the in-situ characterization of catalyst synthesis and catalytic reactions. (C) 2003 Elsevier Science (USA). All rights reserved.

Performance of palladium-containing supported catalysts in the oxidation of 1-butene

Performance of palladium-containing supported catalysts in the oxidation of 1-butene was investigated in a fixed-bed flow microreactor. The Pd-Fe-HCl/Ti-Al catalyst is the best among the five Pd-Fe-HCl/X (A = SiO2, gamma-Al2O3, Al-Ti, TiO2, MCM-22) catalysts for the oxidation of I-butene to butanone. It is interesting that high propionic acid selectivity can be obtained when V and H2SO4 are added to the palladium-containing supported catalysts.

Improvement of Pt catalyst for soot oxidation using mixed oxide as a support

Catalytic activity of Pt catalysts for soot oxidation was studied using temperature programmed reactions. The activity of Pt loaded over TiO2-SiO2 (Pt/TiO2-SiO2) showed higher activity than other Pt/MOx systems (MOx = TiO2, ZrO2, SiO2, Al2O3. TiO2-ZrO2. TiO2-Al2O3, ZrO2-SiO2, ZrO2-Al2O3, SiO2-Al2O3). The activity was highest when the molar ratio of TiO2/(TiO2 + SiO2) ranged from 0.4 to 0.7. The effect of pretreatment with a gas containing low SO2 concentrations on the activity was compared for Pt/SiO2, Pt/TiO2 and Pt/TiO2-SiO2. In the case of Pt/TiO2-SiO2, the activity was markedly promoted by the pretreatment whereas no variation in the activity was observed for Pt/SiO2. The difference in the behavior towards the SO, pretreatment was attributed to property difference in the supports for sulfate accumulation. The high activity of Pt/TiO2-SiO2 was also confirmed under practical conditions with a diesel engine exhaust using a catalyst-supported diesel particulate filter (DPF). (C) 2003 Elsevier Science B.V. All rights reserved.

Synthesis and Characterization of Urea Bridged Hybrid Periodic Mesoporous Organosilica Materials

Urea bridged organic-inorganic hybrid mesoporous SiO2 materials (U-BSQMs) were synthesized through a sol-gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of Si-29 (Si-29, CP-MAS NMR) and C-13 (C-13 CP NMR) indicated that most of the Si-C bonds are unbroken during the synthesis process.