基于电子回旋共振-等离子体增强金属有机物化学气相沉积技术生长GaMnN稀磁半导体的研究

利用电子回旋共振-等离子体增强金属有机物化学气相沉积 (ECR-PEMOCVD)方法，采用二茂锰(Cp₂Mn)作为Mn源，高纯氮气作为氮源，三乙基镓(TEGa)作为Ga源，在蓝宝石(α-Al₂O₃)(0001)衬底上外延生长GaMnN稀磁半导体薄膜.反射高能电子衍射(RHEED)、X射线衍射(XRD)、原子力显微镜(AFM)表征了GaMnN薄膜的晶体结构和表面形貌.GaMnN薄膜均表现出良好的(0002)择优取向，表明制备的薄膜倾向于     

基于电子回旋共振-等离子体增强金属有机物化学气相沉积技术生长GaMnN稀磁半导体的研究

利用电子回旋共振-等离子体增强金属有机物化学气相沉积 (ECR-PEMOCVD)方法,采用二茂锰(Cp₂Mn)作为Mn源,高纯氮气作为氮源,三乙基镓(TEGa)作为Ga源,在蓝宝石(α-Al₂O₃)(0001)衬底上外延生长GaMnN稀磁半导体薄膜.反射高能电子衍射(RHEED)、X射线衍射(XRD)、原子力显微镜(AFM)表征了GaMnN薄膜的晶体结构和表面形貌.GaMnN薄膜均表现出良好的(0002)择优取向,表明制备的薄膜倾向于 关键词： GaMnN薄膜 稀磁半导体 铁磁性 居里温度     

过渡金属二硼化物的金属K边XAS研究

结合X射线衍射实验(XRD)和金属K边的X射线吸收谱(XAS)研究了过渡金属二硼化物(TiB₂,VB₂和CrB₂).在近边吸收区,除了主吸收峰之外,还观察到了3个弱的边前峰,它们是由于金属吸收原子的3d轨道在D6h配位场下分裂,分裂后的3个d轨道与高层金属原子4p轨道发生杂化而引起的.此外,还根据XRD实验得到的晶格参数初步拟合了金属K边EXAFS谱,得到了一些有意义的结果.     

Zn1-xCoxO稀磁半导体薄膜的结构及其磁性研究

利用X射线吸收精细结构、X射线衍射和磁性测量等技术研究脉冲激光气相沉积法制备的Zn1-zCoxO(x=0.01,0.02)稀磁半导体薄膜的结构和磁性.磁性测量结果表明Zn1-xCoxO样品都具有室温铁磁性.X射线衍射结果显示其薄膜样品具有结晶良好的纤锌矿结构.荧光X射线吸收精细结构测试结果表明,脉冲激光气相沉积法制备的样品中的Co离子全部进入ZnO晶格中替代了部分Zn的格点位置,生成单一相的Zn1-xCoxO稀磁半导体.通过对X射线吸收近边结构谱的分析,确定Zn1-xCoxO薄膜中存在O空位,表明Co离子与O空位的相互作用是诱导Zn1-xCoxO产生室温铁磁性的主要原因.     

XPS研究Nd表面氧化物的生长过程

用X射线光电子能谱(XPS)研究新鲜Nd表面在不同氧气和空气进气量的情况下,表面氧化物的生长过程.发现氧化层由氧化物、氢氧化物及表面化学吸附水三种成分,这三种成分的增加与进气量都存在正比对数关系,氧化物和吸附水在一定进气量后趋于饱和,而氢氧化物持续不断增加,最终氢氧化物占据主要地位. 关键词： X射线光电子能谱(XPS) Nd 氧化     

F8BT薄膜表面形貌及与Al形成界面的电子结构和反应

基于共轭聚合物光电器件的性能与聚合物的表面形貌、分子取向、以及与金属电极形成的界面结构密切相关. 本文利用原子力显微镜(AFM)、同步辐射光电子能谱(SRPES)和近边X射线吸收精细结构谱(NEXAFS)等, 研究了聚(9, 9-二辛基芴并苯噻二唑)(F8BT)薄膜的表面形貌、分子取向及其与Al 电极形成界面过程的结构变化. 结果表明, 在略低于F8BT玻璃转变温度(T_g=130 ℃)条件下对F8BT薄膜进行退火, 可明显增加薄膜的表面粗糙度, 薄膜中F8BT 的分子取向角约为49°, 9, 9-二辛基芴单元(F8)与苯噻唑单元(BT)几乎在同一平面. 在Al/F8BT 界面形成过程中, Al与F8BT中的C, N和S均发生不同程度的化学反应, 并导致价带结构和未占据分子轨道(LUMO)态密度的变化. Al对F8BT进行n型掺杂引起F8BT能带弯曲的同时, 未占据能级被部分占据, 更多的电子将被注入到LUMO+1中. 通过考察价带电子结构、芯能级位移及二次截止边的变化, 绘制了清晰的Al/F8BT界面能级图.     

苝四甲酸二酐在Au(111)表面的取向生长及电子结构研究

利用X射线光电子能谱(XPS),同步辐射紫外光电子能谱(SRUPS),近边X射线吸收精细结构(NEXAFS)以及原子力显微镜(AFM)等技术研究了苝四甲酸二酐(PTCDA)与Au(111)的界面电子结构、PTCDA分子取向及有机薄膜的表面形貌.SRUPS价带谱显示,伴随PTCDA分子的微量沉积(0·5ML),位于费米能级附近Au的表面电子态迅速消失,但却观察不到明显的界面杂化态,这说明PTCDA分子和Au(111)界面间存在弱电子传输过程,但并没有发生明显的化学反应.角分辨NEXAFS以及SRUPS结果证明PTCDA分子是平铺在衬底表面.根据Au4f7/2和C1s峰积分强度随薄膜厚度的变化以及AFM图像可知,PTCDA分子在Au(111)表面是一种典型的Stranski-Krastanov生长模式,即先层状生长,再岛状生长,并且在层状生长到岛状生长的转变过程中,存在有机分子的去润湿过程.     

aodSrTi1-xRuxO3系列类钙钛矿结构氧化物的电子结构研究

利用同步辐射光电子能谱技术研究SrTi_1-xRu_xO₃系列类钙钛矿结构氧化物的电子结构. 通过测量该系列氧化物的光电子能谱(PES)和X射线吸收谱(XAS),得到了SrRuO₃在入射能量53eV时的共振光电子能谱(RPES),SrTi_1-xRu_xO₃中,随着x变化而变化的价带光电子能谱和O 1s的吸收谱.然后参照文献中局部密度近似方法(LDA)模拟计算的能带结构,进行初步的分析和解释.     

茶树叶与根表面的XPS表征

利用X射线光电子能谱(XPS)研究了茶树叶与根的表面化学组成与结构。结果表明,茶树表面主要由C, O, N和Al等四种元素组成,在茶树叶远轴面还有少量的P和F。通过查阅标准图谱数据库、参照木材表面XPS分析结果,对茶树表面测得的C1s结合能采用曲线拟合与分峰,得到三种形态：结合能为285 eV的是C1,来自C—C或C—H,代表角质、蜡质等脂类化合物;C2的结合能在286.35 eV（近轴面）和286.61 eV（远轴面）,是能够与氧形成单键的C—O,主要源于表面的纤维素;C3的结合能为288.04 eV（近轴面）和288.09 eV（远轴面）,为CO基团标志,综合N（1s）的结合能（399～401 eV）和O（1s）的分峰情况,为蛋白质的酰基标志。茶树根表面除含有与叶表面相同的C1(结合能285 eV)、C2（结合能286.49 eV）和C3（结合能288.78 eV）所代表的角质、蜡质、纤维素和蛋白质之外,还出现了结合能为283.32 eV的C5。由于其结合能低于C1,推测为茶树根表面的有机金属形态。茶树叶和根表面没有木材表面具有的羧基C4,说明根系分泌的有机酸游离存在于根表面。对茶树表面O（1s）图谱的拟合结果与C（1s）结果相吻合。计算不同C和O形态所占的比例得知,茶树叶面远轴面含氧基团多于近轴面,呈较高的氧化状态,因此远轴面化学性质较活泼;与叶相比,茶树根的角质和蜡质含量显著降低,含氧基团相对增多,因此化学性质较活泼,适于水分子和其他溶质分子通过。由于蛋白质含量为根表面＞远轴面＞近轴面,表明根表面的湿润度高于叶表面,而远轴面湿润度高于近轴面。存在于茶树表面Al的结合能均大于单质铝72.7 eV,在73.50 eV以上,为Al₂O₃形态,这将增大茶树表面的吸附作用。由于根表面Al₂O₃含量高于叶面,显示根具有更强的吸附能力。     

用XPS研究高灰熔融温度煤灰的矿物结构转化

高灰熔点X煤通过添加钙镁复配(W_CaO/W_MgO=1)助熔剂降低灰熔点,在模拟煤气化过程中制备灰渣,用X射线光电子能谱(XPS)分析不同温度点灰渣中O,Si,Al,Ca,Mg的存在形态及演化过程。认为钙镁复配助熔剂降低灰熔点主要是作用在硅、铝、氧结构变化上,表现为铝元素结构中铝氧配位方式的变化,即四配位的铝氧四面体[AlO₄]和六配位的铝氧八面体[AlO₆]随温度的变化而变化;硅元素结构中SiO₂链的破坏,Ca2+和Mg2+加入会破坏SiO₂链,使得桥氧硅变为非桥氧硅;以及氧元素结构中桥氧键断裂和非桥氧键形成。结合Factsage热力学分析软件,分析了添加钙镁复配助熔剂后,煤灰渣的高温相平衡组成,从矿物的结构变化研究助熔剂的助熔机理。结果表明,添加钙镁复配助熔剂后,Ca2+和Mg2+易与硅氧和铝氧四面体以及铝氧八面体中非桥氧键结合,生成低熔点的长石类矿物和镁质矿物,从而降低煤灰熔融温度。     

Interfacial electronic structure and ion beam induced effect of anatase TiO2 surface modified by Pd nanoparticles

Anatase TiO₂ surface could be modified by Pd nanoparticles using an electrochemical deposition method. Surface morphology, light absorption and interfacial electronic structures were studied by field emission scanning electron microscopy (FE-SEM), UV-visible reflectance absorption, X-ray diffraction (XRD) crystallography, and depth-profiling X-ray photoelectron spectroscopy (XPS). On the basis of XRD patterns, Pd 3d XPS and valance band spectra, the as-deposited overlayer Pd is metallic, with no detectable Pd oxides. The optical band gap of TiO₂ decreases from 3.25 to 3.14 eV upon Pd deposition. The XPS spectra with Ar⁺ ion sputtering show that 4+ oxidation state of Ti dramatically changes to lower (3+ and 2+) oxidation states. As a result of this, oxygen defects are created in the bulk while the oxygen diffuses outward to likely form hydroxyl group on the surface. The Pd 3d XPS peak shifts by +0.6 eV to a higher BE position, and the density of state at the Fermi level is more or less reduced. It appears that the overlayer Pd becomes less metallic, plausibly due to TiO₂ support and/or size effect. No critical interfacial interaction between Pd and TiO₂ was observed by XPS.     

(Fe1-xNix)2P电子结构与磁学特性的X射线近边吸收谱研究

利用X射线近边吸收谱对Fe₂P,Ni₂P及其掺杂物(Fe_1-xNi_x)₂P(x=01,025,05)中Fe,Ni,P的K边进行了研究.结合多重散射理论近边计算,讨论了金属原子不同位置格点3f,3g对近边谱特征的贡献,得出当Ni原子取代Fe原子时将优先占据Fe(3f)格点位置;根据第一性原理对能态的计算发现,不考虑磁性时不同格点P的pDOS未占据态电子结构与P-K近边吸收谱实验相符合;与考虑铁磁性Fe₂P 的DOS相比较后结果显示Fe₂P的磁性主要来源于Fe(3g)格点,铁磁性Ni₂P计算的Ni不同格点原子磁矩均接近于0,与它一般显顺磁性结论相一致. 关键词： X射线近边吸收谱 电子结构 多重散射理论 态密度     

Adsorption and structure of methyl mercaptoacetate on Cu(1 1 1) surface by XPS and NEXAFS spectroscopy

Methyl mercaptoacetate (MA) on Cu(1 1 1) surface was investigated using synchrotron radiation-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. MA adsorbs on the surface via thiolate formation and weak interaction of the carbonyl group with the surface. Two different adsorption states previously reported for methanethiolate and ethanethiolate were confirmed, besides atomic sulfur. NEXAFS measurements support gauche-type conformation of MA whose skeleton lies on the surface.     

XPS and NEXAFS studies of aliphatic and aromatic amine species on functionalized surfaces

The chemical constitution of functionalized supports is an important parameter that determines their performance in a broad range of applications, e.g. for immobilization of biomolecules. Supports with amino functionalized surfaces are also often used for DNA microarray experiments. However, spectral data which have been reported for surfaces with amino functionalities suffer from some inconsistencies. In this article a detailed XPS (X-ray photoelectron spectroscopy) and NEXAFS (Near edge X-ray absorption fine structure) database for amino functionalized surfaces is presented. Amino-terminated surfaces prepared from aliphatic and aromatic aminosilanes or aminothiols and a field sample are considered. Effects of aging in air and damage by radiation are addressed as well.     

Molecular orientation of thiol-derivatized tetraphenylporphyrin on gold studied by XPS and NEXAFS

Tetraphenylporphyrins bearing four linkers consisting of thioacetyl-functionalized carbon chains were immobilized on a gold surface via thiolate-gold bonds using two different preparation routes. The structure of these molecular layers was characterized in detail with synchrotron radiation based core-level spectroscopy, X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results show that the geometry of the molecular layers and the number of linkers that bind to the gold surface depends on the preparation schemes. The deprotection of the linkers through removal of the terminal acetyl group before the molecular adsorption (deprotected systems) resulted in porphyrins bound to the gold surface with on the average three linkers, their normal axis being tilted ∼38° with respect to the surface normal. On the other hand, porphyrin layers prepared directly with the acetyl group still in place on the linkers (protected systems) are made of molecules bound to the gold surface via two linkers on the average. The resulting orientation is more upright, with the normal axis of the porphyrin plane tilted ∼50° with respect to the surface normal. Moreover, NEXAFS measurements revealed that the acetyl deprotected porphyrin layers have a higher degree of ordering than the protected systems.     

Growth mode and molecular orientation of phthalocyanine molecules on metal single crystal substrates: A NEXAFS and XPS study

We report on near-edge X-ray absorption and X-ray photoemission experiments for the large π-conjugated organic molecule metal-free phthalocyanine (H₂Pc) on two different single crystal surfaces. Results from H₂Pc deposited on Ag(1 1 1) at 300 K show a clear linear dichroism indicating that the film grows as islands with the molecules lying essentially flat. On a Ni₃Al(1 1 1) and a cooled Ag(1 1 1) substrate, however, the molecules form a homogeneous film and have an average tilt angle of 45-60°. The different film structure is the result of a different molecule-substrate interaction.     

High resolution XPS study of the large-band-gap semiconductor stibnite (Sb2S3): Structural contributions and surface reconstruction

Conventional X-ray photoelectron spectroscopy (XPS) and synchrotron radiation XPS (SRXPS) were used to probe the chemical state properties of stibnite (Sb₂S₃), a large-band-gap semiconductor of complex structure. The conventional spectra were obtained with a Kratos Axis Ultra XPS with magnetic confinement charge neutralization, which is very effective in minimizing both uniform charging and differential charging on this large-band-gap semiconductor. The narrow linewidths (much narrower than previously obtained) for single doublet fits (e.g. Sb 4d_5/2 of 0.57 eV and S 2p_3/2 of 0.63 eV) enabled the observation of a small peak on the low binding energy side of the Sb 3d and Sb 4d lines. With the aid of the very surface-sensitive Sb 4d SRXPS spectra, these low energy peaks are assigned to small Sb metal clusters at the surface after cleavage; the signal for these clusters increases with X-ray dose on the sample.A detailed analysis of the Sb 4d and S 2p linewidths concludes that the Sb 4d_5/2 linewidth is larger than expected based on the inherent linewidth of the instrument and the Sb 4d lifetime width, and on comparison with the As 3d linewidth (0.52 eV) for the analogous As₂S₃. Also, the S 2p_3/2 linewidth is substantially broader than the Sb 4d_5/2 linewidth. These larger than expected linewidths are due to two structurally distinct Sb atoms and three structurally distinct S atoms in the Sb₂S₃ crystal structure. Accordingly, the Sb 4d and S 2p spectra have been fitted to two and three doublets respectively, and the linewidth for all peaks is 0.53 eV. Using recent molecular orbital calculations, the doublets have been assigned to the different structural Sb and S sites.     

Effects of alloying elements on the electronic structure and ductility of NiAl compounds investigated by X-ray absorption fine structure

The Ni L_3,2-edge spectra of the pure Ni, pure NiAl and alloying-element-doped NiAl compounds were obtained by synchrotron radiation X-ray absorption fine structure (XAFS). Due to orbital hybridization effect, directional covalent-type bonds formed and decreased the ductility during forming NiAl. Combining the XAFS spectra analysis and electronegativity comparison, the effects of alloying elements on the electronic structure and then the ductility of the NiAl compounds were obtained. The results showed that Cr, Co, Mo, Ru and W doping could be beneficial to the ductility by both weakening the directional bonds along the <111> direction and enhancing the d–d interactions of the transition metals–Ni atom pair, namely by the transition from covalent bonds to metallic bonds which was beneficial for dislocation to migrate. The results agreed well with the available experimental data and other theoretical results, proving that the model linking the electronic structure and ductility is reliable and can be used as guidance for alloy design.