Sm富勒烯的价带光电子能谱

用紫外光电子能谱和同步辐射光电子能谱研究了Sm掺杂C₆₀薄膜的价带电子结构.Sm的价电子大部分转移给C₆₀，化学键以离子性为主.对于任何化学配比都没有观察到费米边，所以Sm富勒烯超导相在室温下为半导体性质.获得了很接近单相Sm_2.75C₆₀的样品在费米能级附近的电子态密度分布.固溶相的光电子发射与Sm_2.75C₆₀有明显区别.Sm_xC_{60关键词： 60}的Sm填隙化合物')" href="#">C₆₀的Sm填隙化合物 价带光电子能谱 电子结构     

Yb掺杂C60薄膜的x射线光电子能谱研究

在超高真空系统中制备了C60的Yb填隙化合物薄膜.用x射线光电子能谱研究了Yb和C60结合过程中C1s,Yb4f和Yb4d的变化.利用Yb4f和C1s的谱峰强度确定出相纯样品的化学组分接近Yb2.75C60,这一结果与晶体x射线衍射结果一致.Yb4f和Yb4d的峰形与峰位表明化合物中Yb的价态为Yb2+.相纯样品(Yb2.75C60)的C1s峰位相对于纯C60向低结合能方向移动约0.5eV.C1s结合能减小说明有Yb6s电子转移到C60的最低未充填分子轨道能带上.结合能变化大小及峰宽的具体数值为进一步在薄膜样品上研究Yb2.75C60提供了表征样品的手段.     

Yb掺杂C60薄膜的x射线光电子能谱研究

在超高真空系统中制备了C₆₀的Yb填隙化合物薄膜.用x射线光电子能谱研究了Yb和C₆₀结合过程中C 1s，Yb 4f和Yb 4d的变化.利用Yb 4f和C 1s的谱峰强度确定出相纯样品的化学组分接近Yb_2.75C₆₀，这一结果与晶体x射线衍射结果一致.Yb 4f和Yb 4d的峰形与峰位表明化合物中Yb的价态为Yb²⁺.相纯样品（Yb_2.75C₆₀）的C 关键词： 60的Yb填隙化合物薄膜')" href="#">C₆₀的Yb填隙化合物薄膜 x射线光电子能谱 Yb价态     

X射线光电子能谱

X射线光电子能谱（X-ray photoelectron spectroscopy, XPS）技术也被称作用于化学分析的电子能谱（electron spectroscopy for chemical analysis,ESCA）.XPS属表面分析法,它可以给出固体样品表面所含的元素种类、化学组成以及有关的电子结构重要信息,在各种固体材料的基础研究和实际应用中起着重要的作用.文章简要介绍了XPS仪器的工作原理和分析方法,并给出了XPS在科学研究工作中的应用实例.     

X射线光电子能谱

X射线光电子能谱（X-ray photoelectron spectroscopy，XPS）技术也被称作用于化学分析的电子能谱（electron spectroscopy for chemical analysis，ESCA）．XPS属表面分析法，它可以给出固体样品表面所含的元素种类、化学组成以及有关的电子结构重要信息，在各种固体材料的基础研究和实际应用中起着重要的作用．文章简要介绍了XPS仪器的工作原理和分析方法，并给出了XPS在科学研究工作中的应用实例．     

Yb2.75C60价带光电子能谱

用角积分紫外光电子能谱技术测量了Yb2 75C6 0 薄膜的价带电子态密度分布 .相纯Yb2 75C6 0 样品通过C1s芯态x射线电子谱峰的位移表征 .结果表明Yb2 75C6 0 是半导体 ,在费米能级处几乎没有电子态分布 .Yb 6s电子态和C6 0 LU MO能带的杂化效应不可忽略 ,有部分Yb 6s电子分布在Yb C6 0 杂化能带上 .     

沉积态铀薄膜表面氧化的X射线光电子能谱

含铀(U)薄膜在激光惯性约束聚变的实验研究中有重要的用途.研究其在不同气氛下的氧化性能可以为微靶制备、储存及物理实验提供关键的实验数据.通过超高真空磁控溅射技术制备了纯U薄膜及金-铀(Au-U)复合平面膜,将其在大气、高纯氩(Ar)气及超高真空度环境中暴露一段时间后,利用X射线光电子能谱仪结合Ar~+束深度剖析技术考察U层中氧(O)元素分布及价态,分析氧化产物及机理.结果显示,初始状态的U薄膜中未检测到O的存在.Au-U复合薄膜中的微观缺陷减弱了Au防护层的屏蔽效果,使其在3周左右时间内严重氧化,产物为U表面致密的氧化膜及缺陷周围的点状腐蚀物,主要成分均为二氧化铀(UO_2).在高纯Ar气中纯U薄膜仅暴露6 h后表面即被严重氧化,生成厚度不均匀的UO_2.在超高真空度环境下保存12 h后,纯U薄膜表面也发生明显氧化,生成厚度不足1 nm的UO_2.Ar~+束对铀氧化物的刻蚀会因择优溅射效应而使UO_2被还原成非化学计量的UO_(2-x),但这种效应受O含量的影响.     

双原子填充式skutterudite化合物的结构及X射线光电子能谱分析

用高温熔融、淬火、扩散退火结合放电等离子烧结(SPS)法合成了Ca和Ce复合填充的单相Ca_mCe_nFe_xCo_4-xSb₁₂(m=0.17—0.27，n=0.05—0.25，x=1.5)化合物，并结合Rietveld结构解析以及X射线光电子能谱(XPS)分析研究了两种原子复合填充skutterudite化合物的结构与填充状态.Rietveld结构解析表明，Ca_mCe_nFe_1.5Co_2.5Sb₁₂化合物具有skutterudite结构，Ca和Ce原子填充到了Sb的二十面体空洞中，填充原子热振动参数B_Ca/Ce远大于框架原子的热振动参数B_Fe/Co和B_Sb.XPS元素窄区谱分析结果表明，Sb原子在结构中有五种化学状态，每种化学状态的相对含量主要由总填充分数决定，填充原子Ca在Sb的二十面体空洞出现概率有三种可能，但在中心位置出现的概率最大. 关键词： skutterudite化合物 双原子复合填充 结构 X射线光电子能谱分析     

Yb2.75C60价带光电子能谱

用角积分紫外光电子能谱技术测量了Yb_2.75C₆₀薄膜的价带电子态密度分布.相纯Yb_2.75C₆₀样品通过C1s芯态x射线电子谱峰的位移表征.结果表明Yb_2.75C₆₀是半导体，在费米能级处几乎没有电子态分布.Yb 6s电子态和C₆₀LUMO能带的杂化效应不可忽略，有部分Yb 6s电子分布在Yb-C₆₀杂化能带上. 关键词： 2.75C₆₀')" href="#">Yb_2.75C₆₀ 电子能谱 电子态密度     

FePc与TiO2(110)及C60界面电子结构研究

基于C₆₀受体和有机分子给体的太阳能电池是目前非常重要的一个研究热点, 利用同步辐射真空紫外光电子能谱(SRUPS) 技术研究了酞菁铁(FePc)与TiO₂(110)及C₆₀的界面电子结构, 以及FePc与C₆₀分子混合薄膜的电子结构. SRUPS价带谱显示, FePc沉积在化学计量比与还原态两种不同的TiO₂(110)表面时, FePc分子的HOMO能级均随FePc厚度的变化发生了移动, 而在化学计量比的TiO₂(110)表面位移较大, 同时发生界面能带弯曲, 说明存在从有机层向衬底的电子转移. 在FePc/C₆₀和C₆₀/FePc界面形成过程中, FePc与C₆₀分子的最高占据分子轨道(HOMO)位移大小基本相同. 由界面能级排列发现, 在FePc与C₆₀的混合薄膜中, FePc分子的HOMO与C₆₀分子的最高占据分子轨道能级差较大, 这有利于提高器件开路电压, 改善器件性能.     

Angle-resolved photoemission spectroscopy study on iron-based superconductors

Angle-resolved photoemission spectroscopy （ARPES） has played an important role in determining the band structure and the superconducting gap structure of iron-based superconductors. In this paper, from the ARPES perspective, we briefly review the main results from our group in recent years on the iron-based superconductors and their parent compounds, and depict our current understanding on the antiferromagnetism and superconductivity in these materials.     

Electron attenuation lengths in fullerene and fullerides

Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C₆₀ film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K₃C₆₀, K₆C₆₀, Ba₄C₆₀, Sm_2.75C₆₀ and Sm₆C₆₀ are calculated to help the quantitative analyses of the photoemission spectra for these compounds.     

ELECTRICAL PROPERTIES, EQUATIONS OF STATE AND PHASE TRANSITION IN SOLID C60 AT HIGH PRESSURE

Electrical properties and equations of state in solid C₆₀ at room temperature and high pressure have been studied in a diamond anvil cell using capacitance and resistance measurements and a piston-cylinder type device using P-V measurements, respectively. Experimental results by capacitance and P-V measurements indicate that solid C₆₀ also undergoes a phase transition at room temperature and a lower pressure, about 2GPa. The phase transition may be from a face-centered-cubic to a simple-cubic structure.     

The characterization of Cr secondary oxide phases in ZnO films studied by X-ray spectroscopy and photoemission spectroscopy

X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES), and X-ray photoemission spectroscopy (XPS) were used to characterize the Cr secondary oxide phases in ZnO films that had been prepared using a co-sputtering method. Analysis of the Cr L_3,2-edge XANES spectra reveals that the intensity of white-line features decreases subtly as the sputtering power increases, indicating that the occupation of Cr 3d orbitals increases with Cr concentration in (Zn, Cr)O films. The O K-edge spectra show that the intensity of XANES features of (Zn, Cr)O films is lower than those of ZnO film, suggesting enhanced occupation of O 2p-derived states through O 2p-Cr 3d hybridization. The XES and XPS spectra indicate that the line shapes in the valence band of (Zn, Cr)O films are quite different from those of ZnO and that the Cr₂O₃ phase dominates the spinel structure of (Zn, Cr)O films increasingly as the Cr sputtering power is increased. Over all results suggest that the non-ferromagnetic behavior of (Zn, Cr)O films can be attributed to the dominant presence of Cr₂O₃, whereas the bulk comprise phase segregations of Cr₂O₃ and/or ZnCr₂O₄, which results them the most stable TM-doped ZnO material against etching.     

铁基高温超导体电子结构的角分辨光电子能谱研究

铜氧化物超导体和铁基超导体是人类相继发现的两类高温超导家族,它们的高温超导机理是凝聚态物理领域中长期争论但悬而未决的重大问题.对铁基超导体广泛而深入的研究,以及与铜氧化物高温超导体的对比,对于发展新的量子固体理论、解决高温超导机理、探索新的超导体以及超导实际应用都具有重要意义.固体材料的宏观物性由其微观电子结构所决定,揭示高温超导材料的微观电子结构是理解高温超导电性的前提和基础.由于角分辨光电子能谱技术具有独特的同时对能量、动量甚至自旋的分辨能力,已成为探测材料微观电子结构的最直接、最有力的实验手段,在高温超导体的研究中发挥了重要作用.本文综述了在不同体系铁基超导体中费米面拓扑结构、超导能隙大小和对称性、轨道三维性和选择性、电子耦合模式等的揭示和发现,为甄别和提出铁基超导新理论、解决高温超导机理问题提供重要依据.     

Direct angle resolved photoemission spectroscopy and superconductivity of strained high-T c films

Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (<30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-T _c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain. In overdoped and underdoped in-plane compressed (the strain is induced by the choice of substrate) ≈15 nm thin La_{2 − x} Sr _x CuO₄ (LSCO) films we almost double T _c to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES data under tensile strain exhibit the dispersion that is three-dimensional, yet T _c drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO₂ plane, enhances the two-dimensional character of the dispersion and increases T _c, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual lattice of cuprates is like a ‘Napoleon-cake’, i.e. rigid CuO₂ planes alternating with softer ‘reservoir’, that distort differently under strain, our data rule out all oversimplified two-dimensional (rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced T _c.