Analysis of extraterrestrial particles using monochromated electron energy-loss spectroscopy

A monochromated (scanning) transmission electron microscope was used to analyze individual sub-micron grains within interplanetary dust particles (IDP). Using low-loss and core-loss electron energy-loss spectroscopy, we analyzed fluid and gas inclusions within vesiculated alumosilicate grains. It is shown that nanometer-sized vesicles contain predominantly molecular oxygen (O(2)) beside a small fraction of H(2)O. Low-loss spectra reveal the Schumann-Runge continuum peaking at 8.6 eV and absorption bands reflecting vibrational excitation states of O(2) molecules between the first (12.1 eV) and second (16.1 eV) ionization energy. The presence of oxygen gas is supported by the corresponding oxygen K-edge fine structure. The valence state of Fe in iron-oxide within the IDP was also studied. Low-loss spectra provide qualitative information about the oxidation state of iron consistent with the Fe(2+)/Fe(3+) ratio quantitatively derived from the Fe L(2,3) edge.     

大气压空气脉冲流光放电等离子体发射光谱分析

在大气压条件下采用尖-尖电极放电系统得到了稳定的放电等离子体, 并应用发射光谱方法对放电等离子体进行了实验研究。等离子体发射光谱呈现连续谱背景迭加分立谱的形式。连续谱背景来源于放电等离子体内轫致辐射和复合辐射过程; 分立谱归属为N2 C3∏u →B3∏g , N+, N, O的荧光辐射。N+荧光辐射对应的上能级电子组态为2s22p(2P0)3p和2s22p(2P0)3d, 能级高度介于20 eV和23.6 eV之间。实验还结合时间分辨光谱技术, 对放电等离子体中N2(336.8 nm)、N+(500.5 nm)、N+(399.7 nm)荧光信号进行时间分辨测量。结果表明, N2(336.8 nm)荧光首先出现, N+(500.5 nm、399.7 nm)荧光同时产生, 且滞后N2(336.8 nm)荧光约25 ns。根据时间分辨测量结果和相关参考文献, 文章对放电等离子体中N+的生成通道进行了分析。     

Fourier-ratio deconvolution and its Bayesian equivalent

We discuss how an inner-shell electron energy-loss spectrum can be processed using Bayesian (maximum-entropy or maximum-likelihood) deconvolution to simultaneously remove plural scattering and improve the energy resolution. As in Fourier-ratio deconvolution, a low-loss spectrum (recorded from the same area of specimen) is used as a kernel or resolution function. This procedure avoids the need to record the zero-loss peak in the absence of a specimen and uncertainties related to the width of the zero-loss peak. Unlike the case of Fourier-ratio deconvolution, we find that core-loss data do not require pre-edge background subtraction and extrapolation towards zero intensity; simply matching the intensity at both ends of the region is usually sufficient to avoid oscillatory artifacts. Using the low-loss spectrum as both data and kernel yields a zero-loss peak whose width provides an indication of the energy resolution as a function of the number of iterations. Finally, we argue that Fourier-ratio deconvolution or its Bayesian equivalent is the correct way to remove the substrate or matrix contribution to an energy-loss spectrum recorded from a particle on a substrate or embedded in a matrix.     

Influence of ultra-thin TiN thickness(1.4 nm and 2.4 nm) on positive bias temperature instability(PBTI)of high-k/metal gate nMOSFETs with gate-last process

The positive bias temperature instability(PBTI) degradations of high-k/metal gate(HK/MG) n MOSFETs with thin Ti N capping layers(1.4 nm and 2.4 nm) are systemically investigated. In this paper, the trap energy distribution in gate stack during PBTI stress is extracted by using ramped recovery stress, and the temperature dependences of PBTI(90?C,125?C, 160?C) are studied and activation energy(Ea) values(0.13 e V and 0.15 e V) are extracted. Although the equivalent oxide thickness(EOT) values of two Ti N thickness values are almost similar(0.85 nm and 0.87 nm), the 2.4-nm Ti N one(thicker Ti N capping layer) shows better PBTI reliability(13.41% at 0.9 V, 90?C, 1000 s). This is due to the better interfacial layer/high-k(IL/HK) interface, and HK bulk states exhibited through extracting activation energy and trap energy distribution in the high-k layer.     

5d过渡金属原子掺杂氮化铝纳米管电子结构、磁性性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理计算方法, 研究了5d过渡金属原子(Lu、Hf、Ta、W、Re、Os、Ir、Pt、Au、Hg)取代AlN纳米管(AlNNTs)中的铝原子或氮原子时体系的几何结构、电子结构和磁性性质; 并且以理想AlN纳米管(AlNNTs)、Al缺陷体系(VAl)和N缺陷体系(VN)的结果作为对比. 研究发现: 5d 原子取代Al(Al5d)时体系的局域对称性接近于C3v, 但是取代N(N5d)时体系的局域对称性偏离C3v对称性较大; 当掺杂的5d元素相同时, Al5d的成键能比N5d的成键能大; 当掺杂体系相同时(Al5d或N5d), 其成键能基本上随着5d原子的原子序数的增大而降低; 掺杂体系中出现了明显的杂质能级, 给出了态密度等结果; 不同掺杂情况的磁矩不同, 总磁矩呈现出较强的规律性. 利用C3v对称性和分子轨道理论解释了过渡金属原子取代Al时杂质能级的产生和体系磁性的变化规律.     

5d过渡金属原子掺杂氮化铝纳米管电子结构、磁性性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理计算方法, 研究了5d过渡金属原子(Lu、Hf、Ta、W、Re、Os、Ir、Pt、Au、Hg)取代AlN纳米管(AlNNTs)中的铝原子或氮原子时体系的几何结构、电子结构和磁性性质; 并且以理想AlN纳米管(AlNNTs)、Al缺陷体系(VAl)和N缺陷体系(VN)的结果作为对比. 研究发现: 5d 原子取代Al(Al5d)时体系的局域对称性接近于C3v, 但是取代N(N5d)时体系的局域对称性偏离C3v对称性较大; 当掺杂的5d元素相同时, Al5d的成键能比N5d的成键能大; 当掺杂体系相同时(Al5d或N5d), 其成键能基本上随着5d原子的原子序数的增大而降低; 掺杂体系中出现了明显的杂质能级, 给出了态密度等结果; 不同掺杂情况的磁矩不同, 总磁矩呈现出较强的规律性. 利用C3v对称性和分子轨道理论解释了过渡金属原子取代Al时杂质能级的产生和体系磁性的变化规律.     

少量氩气对大气介质阻挡放电光谱的增强

采用双水电极介质阻挡放电装置,测量了大气介质阻挡放电的光谱,并研究了加入少量氩气后光谱的变化。在300～800 nm波长范围内,发现了氮分子(C3Π_u(v′=0)→B3Π_g(v″=0～4))的光谱和氮原子(4d4D_7/2→3p4P0_1/2)的光谱。在大气中加入少量氩气后,击穿电压明显降低,在相同电压条件下,氮分子光谱线和氮原子光谱线强度都增强。同时,加入氩气后上述谱线的半宽度明显加大。由于谱线的Stark加宽与电子密度成正比, 说明加入氩气后等离子体的电子密度增大, 使得电子碰撞激发氮分子及氮原子的概率增大,激发到较高激发态的氮原子或氮分子增多,从而使光谱强度增强。     

Structural stability of heat-treated CoN/CN soft X-ray multilayers fabricated by dual-facing-target sputtering

286 , 176 (1996)]. (1) The interdiffusion critical wavelengths were calculated as 2.00–2.04 nm at temperatures ranging from 473 to 523 K, which is equal to those of Co/C multilayers within the experimental error, indicating that the interdiffusion behaviours in the CoN/CN multilayers are still decided by the thermodynamic properties of the Co-C system. (2) The effective interdiffusivities and macroscopic diffusion coefficients are smaller. (3) The activation energy for diffusion is larger. The features imply that it is possible to improve the thermal stability of Co/C multilayers by doping with N atoms. The high-temperature annealing results imply that the destructive threshold of the CoN/CN multilayers is 100–200 °C higher than that of Co/C multilayers. The small-angle X-ray diffraction of CoN/CN soft X-ray multilayers indicates that the period expansion of the multilayers is only 4% at 400 °C, and the interface pattern still exists even if they were annealed at 700 °C. The large-angle X-ray diffraction and transmission electron microscopy analysis reveal that the crystalline process is significantly retarded if doped with N atoms, leading to a smaller grain size at higher annealing temperatures. The significant improvement of the thermal stability can be interpreted with Raman spectroscopy and X-ray photoelectron spectroscopy analysis. The Raman spectra give the evidence that the formation of the sp³ bonding in the CN sublayers can be suppressed effectively by doping with N atoms, and thus the period expansion resulting from the changes in the density of CN layers can be decreased considerably. The X-ray photoelectron spectra give information about existence of the strong covalent bonding between N atoms and the ionic bonding between Co and N atoms, which can slow down the tendency of the structural relaxation. The interstitial N atoms decrease the mobility of Co atoms, and thus the fcc Co and hcp Co coexist even though the annealing temperature is much higher than the phase transformation temperature of 420 °C, leading to the suppression of the grain growth. Received: 29 May 1997/Accepted: 8 September 1997     

PTCDA/ITO表面和界面的X射线光电子能谱分析

利用X射线光电子能谱对PTCDA/p-Si有机/无机光电探测器中PTCDA/ITO表面和界面进行了测试分析。结果表明,苝环上的C原子的结合能为284.6 eV,酸酐中的C原子的结合能为288.7 eV,并存在来源于ITO膜中的氧对C原子的氧化现象,界面处C(1s)谱中较高结合能峰消失,且峰值向低结合能发生化学位移;CO键中O原子的结合能为531.5 eV,C—O—C键中的O原子的结合能为533.4 eV。     

苝四甲酸二酐的真空升华提纯及其光谱测试与分析

纯度为9.75%的有机半导体材料苝四甲酸二酐(PTCDA),在其升华点进行了真空升华提纯,其纯度可达99.9%。利用质谱、红外光谱及X光电子能谱对这种高纯材料进行了测试并详细分析了其分子结构、化学键的形成、原子在晶格平衡位置的振动模式、电子的组态和原子的结合能的变化。由红外光谱分析得出,苝四甲酸二酐的分子结构是中央5个C构所组成的苝核基团及位于苝核两端的两个酸酐组成,它们主要以共价键结合。晶格上的C原子在其平衡位置主要以伸缩振动为主。其分子中有大量可以自由移动的π电子;分子间离域大π键的交叠决定了苝四甲酸二酐的导电性能。由XPS谱分析得出,高纯度的苝四甲酸二酐中有结合能不同的两种C原子,结合能分别为：285.3和288.7 eV。它们对应于苝环及酸酐上的C原子。另外,有两种类型的O原子,即CO和C—O—C,其结合能分别为531.3和533.1 eV。     

大气环境下氩气空心针-板放电中OH和O的空间分布

研究了大气环境下氩气空心针-板放电等离子体中OH和O的空间分布。利用空心针-板放电装置,得到了3cm长的等离子体炬。首先采集了300～800nm范围内的光发射谱,发现除了ArⅠ谱线、N2第二正带系谱线C3Πu(ν′=0)→B3Πg(ν″=0)外,还出现了OH自由基的谱带、OⅠ谱线和较弱的H谱线。由于含氧活性粒子在材料表面改性中具有重要作用,实验选取了OH发射的309nm附近的谱带和激发态O发射的777.4nm谱线,分析了它们的相对强度,得到了粒子的空间分布。结果表明:沿等离子体从弧根到弧梢位置,OH自由基数量迅速减少,O原子数量呈现先增多后减少的规律。     

TiO2/SiO2的表面化学修饰及其DRS和Raman光谱分析

以氯化醇钛盐表面反应法制备系列TiO2/SiO2,根据XRD,Raman和DRS表征分析,载体表面具有分子级分散的锐钛矿型TiO2微晶粒子和非晶TiOx物种.与本体TiO2相比,TiO2/SiO2的吸收带边显著蓝移,能隙增大为3.96 eV.当金属M(M:Pd,Cu和Ni)负载于TiO2/SiO2表面,可使其光吸收域扩展到可见光区,并引起吸收带边红移.相对Pd的负载,Cu,Ni的负载对TiO2/SiO2的LMCT带影响更大,其中Cu-TiO2/SiO2的能隙减小为3.68 eV.当金属氧化物MoO3负载于TiO2/SiO2上时,可以调变TiO2/SiO2的吸收带边并增强对可见光的吸收;随MoO3载量的增加,表面物种的相互作用增强,形成Mo-O-Ti复合结构,增强了LMCT带的吸收强度,并使能隙减小为3.81 eV.     

低介电常数非晶氟碳薄膜光谱表征

以C4F8和CH4为原料气,通过等离子体增强化学气相淀积的方法制备了非晶氟碳薄膜,在实验条件下所得薄膜的介电常数为2.3。薄膜的傅里叶变换红外光谱表明该薄膜中除了含有CFn(n=1-3）基团外,还含有少量的C=O,C=C等不饱和双键,没有迹象表明C-H和O-H的存在。X射线光电子能谱进一步证明了薄膜中的碳元素有六种不同的化学状态分别为CF3（8%）、CF2（19%）,CF（26.7%)、C↓-—CF。（42.5%),C↓-—C(3.3%)和C=O（0.5%),表明薄膜中大约54%的碳原子与氟成键,大约43%的碳原子不是与氟成键,而是与碳氟基团CFn中的碳原子成键,毗连的两个碳原子上均没有氟参与成键的几率很小。     

Properties of isolated DNA bases, base pairs and nucleosides examined by laser spectroscopy

The vibronic spectra of laser desorbed and jet cooled guanine (G) adenine (A), and cytosine (C) consist of bands from four, two and two major tautomers respectively, as revealed by UV-UV and IR-UV double resonance spectroscopy. The vibronic spectrum of adenine around 277 nm consists of weak nπ^* and strong ππ^* transitions, based on IR-UV and deuteration experiments. Precise ionization potentials of G and A were determined with 2-color, 2-photon ionization. We also measured vibronic and IR spectra of several base pairs. GC exhibits a HNH ^... OH/NH ^... N/C=O ^... HNH bonding similar to the Watson-Crick GC base pair but with C as enol tautomer. One GG isomer exhibits non-symmetric hydrogen bonding with HNH ^... N/NH ^... N/C=O ^... HNH interactions. A second observed GG isomer has a symmetrical hydrogen bond arrangement with C=O ^... NH/NH ^... O=C bonding. Two CC isomers were observed with symmetrical C=O ^... NH/NH ^... O=C bonding and nonsymmetrical C=O ^... HNH/NH ^... N interaction, respectively. Guanosine (Gs), 2-DeoxyGs und 3-DeoxyGs each exhibit only one isomer in the investigated wavelength range around 290 nm with a strong intramolecular sugar(5-OH) ^... enolguanine(3-N) hydrogen bond. Received 16 June 2002 / Received in final form 15 July 2002 Published online 13 September 2002     

Ti, C, N在α-Fe基中的合金化效应及对键合性质的影响

基于第一性原理赝势平面波方法研究了合金元素Ti, C, N对α-Fe基电子结构及键合性质的影响, 计算了含Ti, C, N的Fe基固溶体的总能量、结合能, 分析了态密度、电荷布居数、交叠布居数和电荷密度, 从理论上解释了在Fe基中固溶Ti, C, N后其性能改善的原因. 结果表明, 随着Fe基固溶体中Ti(0-12.5 at%), C(0-11.11 at%), N(0-11.11 at%)含量增加, 结合能略有增加; Ti, C, N的固溶使各Fe基固溶体在费米能级处强烈成键, 结合能力增强, 并且在费米能级附近出现赝能隙, 表明固溶体中金属键与共价键共存; 随着Ti, C, N含量的增加, C, N分别与Ti, Fe之间的共价键结合强度加强, 部分C, N原子会与Ti原子结合形成TiC, TiN颗粒, 起到沉积相颗粒强韧化作用.     

C,N, O原子在金属V中扩散行为的第一性原理计算

基于密度泛函理论, 采用第一性原理计算方法研究了C, N, O原子在金属V中的扩散行为. 首先, 讨论了C, N, O原子在V体心立方晶格中的间隙占位情况, 分析了其在间隙位置与V晶格的相互作用, 并探究了这种相互作用对金属V电子结构的影响. 研究结果表明: C, N, O原子在V的八面体间隙位置更为稳定, 并且C, N, O原子的2p电子与V的3d电子之间有比较强的成键作用; C, N, O原子的扩散势垒分别为0.89, 1.26, 0.98 eV, 并得出了其扩散系数表达式; 最后, 通过阿仑尼乌斯关系图对比了三者在V中扩散系数的大小, 并计算出体系温度在500–1100 K之间时其在V中的扩散系数, 计算结果与实验值基本符合.     

Ti原子与氮掺杂金刚石(001) 界面结合强度的第一性原理研究

摘 要：金属钛原子在金刚石表面的结合强度直接影响金刚石真空介电窗口的使用性能和寿命. 本文通过基于密度泛函理论的第一性原理方法研究了Ti原子与不同氮掺杂位置的金刚石（001）界面的结合能、电荷分布和稳态几何结构. 结果表明：Ti原子与N原子取代掺杂在第二层C原子处金刚石表面的结合能比未掺杂和掺杂在第三层的结合能都高,达到-7.293 eV,使得金刚石表面形成的界面结构更加稳定,结合强度更好;通过电荷分布分析,N原子掺杂在第二层金刚石表面的Ti原子上的电荷转移最明显,对金刚石表面碳原子吸附最强,也具有更好的结合强度. 与未掺杂金刚石表面形成的Ti-C键键长相比,N掺杂在第二层和第三层C原子处金刚石表面形成的Ti-C键键长比前者分别长0.051 Å和0.042 Å,略有增加.     

四方相BaTiO3铁电性的第一性原理研究

在广义梯度近似下，利用超软赝势对立方相和四方相BaTiO3晶胞中Ti原子沿c轴位移时体系的能量、原子间电子云重叠布局数和各原子上的净电荷等进行了自洽计算.结果显示，当Ti原子沿c轴位移0012nm时，四方相BaTiO3体系能量最低，其自发极化强度为0261C/m2，该结果与实验数据相符合；同时表明，O原子的2p轨道和Ti原子的3d轨道的杂 化是BaTiO3晶体出现铁电性的重要原因. 关键词： 四方相BaTiO3 铁电性 位移 态密度     

CuPc/ITO结构的表面和界面电子态的XPS研究

覆盖有Indium tin oxide(ITO)膜的透明导电玻璃广泛地用作有机发光器件 (OLEDs)的空穴注入电极 ,但是ITO膜的功函数通常与空穴传输材料的最高被占据分子轨道 (HOMO)不匹配。铜酞菁 (CuPc)作为缓冲层可以提高空穴从ITO向空穴传输材料的注入效率。对CuPc ITO样品的XPS表面分析表明 ,在CuPc分子中 ,铜原子显 2价 ,通过配位键和氮原子相互作用。CuPc分子中有两类碳原子 :8个C原子与 2个N原子成键 ;其余 2 4个C原子具有芳香烃性质。N原子也处在两种化学环境中 :有 4个N原子只与 2个C原子形成CNC键 ;另外 4个N原子不仅与 2个C原子成键 ,还通过配位键与Cu原子成键。用氩离子束对样品表面进行了溅射剥蚀 ,当溅射时间分别为 2 ,5 ,10min时进行XPS采谱分析 ,结果表明 ,随着氩离子束溅射时间增长 ,C 1s,N 1s峰变弱 ,Cu 2p ,O 1s,In 3d,Sn 3d峰增强 ,C 1s,N 1s,O 1s,In 3d和Sn 3d峰都向高束缚能或低束缚能方向移动 ,但它们的情况却不相同。     

RE(POA)3phen配合物的合成、表征及荧光性能

合成了以稀土离子Sm³⁺、Eu³⁺、Tb³⁺、Dy³⁺及Tb³⁺为发光中心,以苯氧乙酸(HPOA)和邻菲罗啉(phen)为配体,掺杂La³⁺、Gd³⁺、 Y³⁺的7种稀土配合物, 对配合物进行了C、H、N元素分析、稀土络合滴定、红外光谱、紫外光谱和发光光谱的研究。结果表明配合物的组成分别为SmL₃L'·1/2H₂O,EuL₃L'·1/2H₂O,TbL₃L'· 1/2H₂O,DyL₃L'·1/2H₂O,掺杂配合物组成分别为Tb_0.5Gd_0.5L₃L'·1/2H₂O,Tb_0.5Y_0.5L₃L'·1/2H₂O,Tb_0.5La_0.5L₃L'·1/2H₂O(L=C₆H₅OCH₂COO^-, L'=phen)。配合物中的稀土离子与苯氧乙酸中羧基的一个氧原子和苯氧基的氧原子配位,与邻菲罗啉中的两个氮原子配位成键;荧光光谱表明,铽三元配合物的发射强度要远大于其它三元配合物的发光强度,掺杂发光惰性稀土离子La³⁺、Gd³⁺、Y³⁺的铽配合物中,Y³⁺掺杂配合物的发光强度有所增强。