Interlayer segregation in magnetic multilayers and its influence on exchange coupling

Experimental results show that the exchange coupling field (H-ex) of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. X-ray photoelectron spectroscopy shows that Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. While studying Ta/X(X=Bi,Pb,Ag,In)/NiFe/FeMn multilayers, we also find that X atoms segregate to the NiFe/FeMn interface, which results in a decrease of the H-ex. However, a small amount of Bi, Pb, etc. deposited between Cu and pinned NiFe layer for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers can increase H-ex. (C) 2003 American Institute of Physics.

Magnetic property and interlayer segregation in spin valve metal multilayers

The experimental results show that the exchange coupling field of NiFe/FeMn for Ta/ NiFe/FeMn/Ta multilayers is higher than that for the spin valve multilayers Ta/NiFe/Cu/NiFe/FeMn/ Ta. In order to find out the reason, the composition and chemical states at the surfaces of Ta(12nm)/ NiFe(7nm), Ta(12nm)/NiFe(7nm)/Cu(4nm) and Ta(12nm)/NiFe(7nm)/Cu(3nm)/NiFe(5nm) were studied using the X-ray photoelectron spectroscopy (XPS). The results show that no elements from lower layers float out or segregate to the surface for the first and second samples. However, Cu atoms segregate to the surface of Ta(12nm)/NiFe(7nm)/Cu(3nm)/NiFe(5nm) multilayers, i.e. Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors causing the exchange coupling field of Ta/NiFe/FeMn/Ta multilayers to be higher than that of Ta/NiFe/Cu/NiFe/ FeMn/Ta multilayers.

Interlayer segregation of Cu atoms in Ta/NiFe/Cu/NiFe/FeMn/Ta spin-valve multilayers and its influence on magnetic properties

Experimental results show that the exchange coupling field (H-ex) of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. In order to find out the reason, the composition and chemical states at the surface of Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/Cu(4 nm), and Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) were studied using x-ray photoelectron spectroscopy. The results show that no elements from lower layers float out or segregate to the surface in the first and second samples. However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) multilayers, i.e., Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which causes the exchange coupling field (H-ex) of Ta/NiFe/Cu/NiFe/FeMn/Ta to be weaker than that of Ta/NiFe/FeMn/Ta. (C) 2002 American Institute of Physics.

Interlayer segregation of Cu atoms in metal multilayers

The experimental results show that the exchange coupling field H.. of NiFe/FeMn for TalNiFe/FeMn/Ta multilayers is higher than that for the spin valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. The composition and chemical states at the surface of Ta(12nm)/NiFe(7nm), Th(12nm)/NiFe(7nm)/Cu(4nm) and Ta(12nm)/NiFe(7nm)/Cu(3 nm)/NiFe(5 mn) were studied by using x-ray photoelectron spectroscopy. The results show that no element from the underlayers Boats out or segregates to the surface for Th(12 nm)/NiFe(7nm), Ta(12 nm)/NiFe(7nm)/Cu(4 mn). However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7nm)/Cu(3nm)/NiFe(5nm) multilayers, i.e. to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which will cause the exchange coupling field H.. of Ta/NiFe/FeMn/Ta multilayers to be higher than that of Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers.

Excitation transfer in vertically self-organized pairs of unequal-sized InAs/GaAs quantum dots

The excitation transfer processes in vertically self organized pairs of unequal-sized quantum dots (QD's), which are created in InAs/GaAs bilayers with different InAs deposition amounts in the first and second layers, have been investigated experimentally by photoluminescence technique. The distance between the two dot layers is varied from 3 to 12 nm. The optical properties of the formed pairs of unequal-sized QD's with clearly discernible ground-state transition energy depend on the spacer thickness. When the spacer layer of GaAs is thin enough, only one photoluminescence peak related to the large QD ensemble has been observed as a result of strong electronic coupling in the InAs QD pairs. The results provide evidence for nonresonant energy transfer from the smaller QDs in the second layer to the larger QD's in the first layer in such an asymmetric QD pair.

Structural characterization of InGaAs/GaAs quantum dots superlattice infrared photodetector structures

InGaAs/GaAs quantum dots (QDs) superlattice grown by molecular beam epitaxy (MBE) at different substrate temperatures for fabricating 8-12 mu m infrared photodetector were characterized by transmission electron microscopy (TEM), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL). High-quality QDs superlattice can be achieved by higher growth temperature. Cross-sectional TEM shows the QDs in the successive layers are vertically aligned along growth direction. Interaction of partial vertically aligned columns leads to a perfect vertical ordering. With increasing number of bilayers, the average QDs size becomes larger in height and rapidly saturates at a certain value, while average lateral length nearly preserves initial size. This change leads to the formation of QDs homogeneous in size and of a particular shape. The observed self-organizations are attributed to the effect of strain distribution at QDs on the kinetic growth process. DCXRD measurement shows two sets of satellite peaks which corresponds to QDs superlattice and multi quantum wells formed by the wetting layers. Kinematical simulations of the wetting layers indicate that the formation of QDs is associated with a decrease of the effective indium content in the wetting layers. (C) 1999 Elsevier Science B.V. All rights reserved.

Nano-Ag on vanadium dioxide. I. Localized spectrum tailoring

We report on the utilization of localized surface plasmon resonance (LSPR) of Ag nanoparticles to tailor the optical properties Of VO2 thin film. Interaction of nano-Ag with incident light yields a salient absorption band in the visible-near IR region and modifies the spectrum Of VO2 locally. The wavelength of modification occurs in a limited spectral region rather than affects the full spectrum. The wavelength of modification shows a strong dependence on the metal nanoparticle size and shifts toward the red as the particle size or the mass thickness of nano-Ag increases. Also, we found that the wavelength can be shifted into the IR further by introducing a thin layer of TiO2 onto the nano-Ag. Interestingly, with the help of LSPR effects the VO2 film exhibits an anomalous thermochromic behavior in the modification wavelength region, which may be useful in optical switching applications.

三价金属离子（AE~(3+)、Al~(3+)）及其配合物与磷脂双分子膜的作用研究

本文用二维核磁共振、富利叶变换拉曼光谱和差示扫描量热等方法研究了：1）稀土离子与柠檬酸配体的溶液配位行为，并用顺磁位移试剂的方法计算了该条件下的配合物形成稳定常数；2）稀土离子及其配合物与不同种类的磷脂分子的作用；3）二氧化硅和柠檬酸铝与DPPC脂质体的作用。

脂膜内磷脂与分子和离子相互作用的光谱研究

本文以磷脂的脂质体和LB膜两大膜模拟体系为模型，利用红外光谱等技术手段，研究了稀土离子、氨基酸及氨基酸稀土配合物对磷脂脂质体热致相变行为的影响以及它们同磷脂相互作用的分子机理；同时对磷脂LB膜作了结构表征，研究了磷脂LB膜与蛋白质的相互作用。

石油污染土壤微生物多样性分析及芘降解菌的鉴定

石油污染是目前最严重的环境问题之一，我国有近千万亩的耕地受到程度不同的石油污染。沈抚灌区位于辽宁省沈阳市和抚顺市之间，全长70多千米，是我国最大的石油污染灌区之一，有四五十年的污灌历史，已对当地的生态环境造成了严重的影响。随着人们对污水灌溉危害的认识，从20世纪80年代起，逐步停止了污水灌溉，开始了清水灌溉和改为旱田耕作，但污染问题仍然存在。目前，由于对该地区污染土壤微生物类群、原位降解菌及它们对环境条件变化的响应等信息缺乏了解，限制了对该地区污染土壤的生物修复。 分子生物学研究手段及稳定同位素分析技术，为污染土壤微生物生态学研究提供了全新的研究手段，为突破当前石油污染土壤生物修复研究止步不前的局面指引了方向。本论文采用变性梯度凝胶电泳（Denaturing Gradient Gel Electrophoresis, DGGE）和磷脂脂肪酸分析（Phospholipid Fatty-acid Analysis, PLFA）分析技术，对沈抚灌区水改旱田石油污染土壤的微生物多样性与环境指标的相关规律进行了分析；以PLFA为生物标示物，结合气相色谱-稳定同位素比率质谱（Gas Chromatography Combustion Isotope Ratio Mass Spectrometry, GC-c-IRMS）分析技术，对石油污染土壤和相对清洁土壤中多环芳烃菲和芘的土著降解菌群进行了鉴定；并以不同的吸附性载体为介质，富集、筛选了芘的降解菌。 研究结果表明，石油污染土壤中的微生物群落结构主要与其相对地理位置有关，当污染物的浓度达到一定程度，土壤中的微生物群落结构会发生明显的改变。以13C标记的稳定同位素菲和芘为代谢底物，对污染土壤中菲和芘的土著降解菌群进行了鉴定。 13C-PLFA- GC-c-IRMS分析结果显示，参与菲降解的微生物有G-、G+细菌和放线菌，其中以G-细菌为主；污染土壤和相对清洁土壤两种土壤都未检出有真菌参与；参与芘降解的微生物有放线菌、G-细菌和真菌，其中以G-细菌为主，同时，也检测到有真菌的参与；污染土壤中的降解菌群较清洁土壤丰富。研究还发现，芘在土壤中的降解可能存在不经过菲为中间产物的代谢途径。采用不同的吸附性载体所富集的优势细菌显著不同。从不同的吸附性载体上最终得到8株芘的降解菌，其中鉴定出的三株菌中Sp-A56，Sp-A21为多食鞘氨醇杆菌（Sphingobacterium multivorum）；Sp-B05氨基杆菌属的一个亚种（Aminobacter sp.），未见有关该菌株芘降解能力的报道，可能是一株新的芘降解菌。

黑土中乙草胺吸附、迁移及微生物降解研究

东北黑土区是我国重要的商品粮生产基地，在保证我国的粮食安全中发挥着重要作用。随着生产的发展，多种农用化学品尤其是大量杀虫剂和除草剂进入黑土农田环境，在预防作物病虫害及减少人工劳动强度的同时，这些化学品在环境中会发生一系列复杂的物理、化学和生物化学反应，使黑土面临着环境安全危机。因此，研究农用化学品的土壤生态过程与黑土农田生态系统环境安全有关的科学问题显得尤为重要。 本文以东北地区广泛使用的除草剂乙草胺为代表，在推荐施用量条件下，通过室内恒温（25℃）避光培养试验，研究了乙草胺在黑土中的主要生态过程（降解、吸附）及在土壤中的残留时间特征，探讨了影响乙草胺生态过程行为的主要因素，同时利用磷脂脂肪酸（Phospholipid Fatty Acids，PLFAs）为标识物研究了土壤微生物对外源污染物的的响应。 研究结果表明：吸附是乙草胺在土壤中主要去向之一，高有机质黑土对乙草胺的吸附能力很强。微生物降解是乙草胺消失的另一个重要要因素，适当的水分有益于土壤中微生物生长，从而促进土壤中乙草胺降解，其中，细菌比真菌具有更强的降解乙草胺的能力；随着乙草胺的施药量增加，乙草胺总降解率下降。在乙草胺施入及降解过程中，土壤微生物群落不断发生变化，真菌PLFAs、细菌PLFAs；G+菌PLFAs、G-菌PLFAs数量及比例受到乙草胺施入的显著影响，细菌比真菌的变化更为显著。原位土壤中，乙草胺在表层土壤（0-10cm和10-20cm）微生物降解作用显著；而降水是促进乙草胺向深层次迁移的主要因素。 通过对乙草胺的主要生态过程进行研究，对深入探讨乙草胺生态环境安全性及合理使用除草剂有着重要的指导作用。

黑土微生物活力与组成对养分添加的响应

东北黑土是我国重要的商品粮生产基地，在保证我国的粮食安全中起着重要作用。鉴于东北黑土所具有的重要战略地位及其面临的严峻形势，如何通过化肥合理配施培肥黑土已经成为一个亟待解决的关键问题。 本文以东北黑土为供试土壤，设置CK、C、N、P、NP、CN、CP、CNP，8个养分组合，进行室内恒温模拟培养。通过对黑土呼吸强度的监测，研究黑土微生物活力对不同养分响应的规律；同时采用磷脂脂肪酸（Phospholipid Fatty Acids, PLFAs）和中性脂肪酸（Neutral Lipid Fatty Acids, NLFAs）为标识物，研究黑土微生物群落结构以及生理生态特性在不同养分条件下的动态变化，揭示黑土微生物活力与群落组成对不同养分响应的规律。 研究结果表明：黑土微生物活力首先受到可利用C源的限制，单加葡萄糖能够使土壤呼吸释放的CO2-C累积量达到对照的10倍以上，使黑土微生物活力显著提高；而在碳限制的状况被缓解后，氮便成为黑土微生物生长的主要限制因素，可利用碳底物充足的条件下，N的加入能够显著提高土壤呼吸强度，使释放出的CO2-C累积量达到对照处理的13倍以上，CN交互作用非常显著；在碳氮养分都充足的条件下，P的施入能更好地刺激微生物生长，提高黑土微生物活力，CNP处理，黑土微生物活力在培养的第3 d即达到峰值。CN和CNP组合能够迅速刺激真菌、细菌生长，使PLFA和NLFA含量、真菌/细菌比值均增加；并且CNP组合优于CN组合。单独加入C和CP组合，不能在短时间内使真菌、细菌的PLFA和NLFA含量显著增加，真菌/细菌比值也处于较低的水平。G+/G-比值在CN条件下，达到最大之后逐渐趋于平稳；而在单加C、CP和CNP条件下，G+/G-比值均在培养时间内达到两次峰值，显示出不同的养分条件下，微生物群落结构发生着内在的动态变化。

Behavior of crystalline silicon under huge electronic excitations: A transient thermal spike description

Recent experimental works devoted to the phenomena of mixing observed at metallic multilayers Ni/Si irradiated by swift heavy ions irradiations make it necessary to revisit the insensibility of crystalline Si under huge electronic excitations. Knowing that Ni is an insensitive material, such observed mixing would exist only if Si is a sensitive material. In order to extend the study of swift heavy ion effects to semiconductor materials, the experimental results obtained in bulk silicon have been analyzed within the framework of the inelastic thermal spike model. Provided the quenching of a boiling ( or vapor) phase is taken as the criterion of amorphization, the calculations with an electron-phonon coupling constant g(300 K) = 1.8 x 10(12) W/cm(3)/K and an electronic diffusivity D-e(300 K) = 80 cm(2)/s nicely reproduce the size of observed amorphous tracks as well as the electronic energy loss threshold value for their creation, assuming that they result from the quenching of the appearance of a boiling phase along the ion path. Using these parameters for Si in the case of a Ni/Si multilayer, the mixing observed experimentally can be well simulated by the inelastic thermal spike model extended to multilayers, assuming that this occurs in the molten phase created at the Ni interface by energy transfer from Si. (C) 2009 Elsevier B. V. All rights reserved.

Guest inducing p-sulfonatocalix[4] arene into three-dimensional capsule architecture and a mixed A-B double layer framework

The reactions of sodium p-sulfonatocalix[4]arene (Na5L) and terbium/europium(III) chloride in the presence of pyrazine-N,N'-dioxide (PNNO) in aqueous solutions gave the crystalline complexes 1 and 2. Both structures contain molecular capsules of p-sulfonatocalix[4] arene with PNNO as guest molecules in the cavity of the calix[4]arenes. The molecular capsules are connected through sodium and terbium (or europium) centers forming a three-dimensional framework.