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 .     

Electronic structure of Yb/H－Si (111) interface

Photoemission spectra are measured for Yb covered surface of wet-chemically-etched H－Si (111). The results reveal that the lattice structure of the H－Si (111) surface is stable against the deposition of Yb atoms. X-ray photoemission spectra indicate the formation of a polarized (dipole) surface layer, with the silicon negatively charged. Ultraviolet photoemission spectra exhibit the semiconducting property of the interface below one monolayer coverage. Work function variation during the formation of the Yb/H－Si (111) interface is measured by the secondary-electron cutoff in the ultraviolet photoemission spectral line. The largest decrease of work function is ～1.65eV. The contributions of the dipole surface layer and the band bending to the work function change are determined to be ～1.15eV and ～0.5eV, respectively. The work function of metal Yb is determined to be ～2.80±0.05eV.     

Yb2.75C60同步辐射光电子能谱

在超高真空系统中制备了Yb275C60薄膜.对样品进行了同步辐射光电子能谱研究.在费米能级以下约5 eV范围内的谱数据由Yb275C60价带（C60分子轨道LUMO，HOMO和HOMO 1导出的能带）和芯态（Yb 4f7/2，4f5/2）能级构成.用紫外能区不同能量的入射光子，用C 2p和Yb 4f光电离截面随光子能量的不同变化规律，通过定量拟合，得到了对谱线有贡献的上述各个组分的峰位、峰宽和强度.结果表明，光子能量高于约300 eV时，芯态4f的贡献使得实验结果远远偏离价带的本征态密度分布.因此，研究Yb275C60价态时，应使用能量低于300 eV的光子.对实验和拟合结果分析，发现了类似纯C60的光电离截面振荡现象.振荡幅度相对于纯C60较小，反映了化合物中C60分子的化学环境对光电离截面振荡现象起着不可忽略的作用. 关键词： Yb275C60 同步辐射光电子能谱 光电离截面振荡     

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     

Yb2.75C60同步辐射光电子能谱

在超高真空系统中制备了Yb2.75C60薄膜.对样品进行了同步辐射光电子能谱研究.在费米能级以下约5 eV范围内的谱数据由Yb2.75C60价带(C60分子轨道LUMO,HOMO和HOMO-1导出的能带)和芯态(Yb 4f7/2,4f5/2)能级构成.用紫外能区不同能量的入射光子,用C 2p和Yb 4f光电离截面随光子能量的不同变化规律,通过定量拟合,得到了对谱线有贡献的上述各个组分的峰位、峰宽和强度.结果表明,光子能量高于约30.0 eV时,芯态4f的贡献使得实验结果远远偏离价带的本征态密度分布.因此,研究Yb2.75C60价态时,应使用能量低于30.0 eV的光子.对实验和拟合结果分析,发现了类似纯C60的光电离截面振荡现象.振荡幅度相对于纯C60较小,反映了化合物中C60分子的化学环境对光电离截面振荡现象起着不可忽略的作用.     

拓扑材料γ-PtBi2的变温晶体结构研究

利用X射线衍射（XRD）、角分辨光电子能谱（ARPES）和能带计算的方法研究了不同温度下γ-PtBi₂的晶体结构。利用单晶XRD确定了室温下晶体的结构为P31m。为了确定低温时样品的晶体结构,用ARPES测得了样品的电子结构并与计算结果进行了对比,结果显示样品的结构与P31m相吻合,这表明在低温时样品依然保持P31m结构。进一步的高温XRD研究表明,在高温时样品的晶体结构仍为P31m结构。     

Electronic structure,Dirac points and Fermi arc surface states in three-dimensional Dirac semimetal Na_3Bi from angle-resolved photoemission spectroscopy

The three-dimensional(3D) Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction band and valence band are connected. They have isolated 3D Dirac nodes in the whole Brillouin zone and can be viewed as a 3D counterpart of graphene. Recent theoretical calculations and experimental results indicate that the 3D Dirac semimetal state can be realized in a simple stoichiometric compound A_3Bi(A = Na, K, Rb). Here we report comprehensive high-resolution angle-resolved photoemission(ARPES) measurements on the two cleaved surfaces,(001) and(100), of Na_3Bi. On the(001) surface, by comparison with theoretical calculations, we provide a proper assignment of the observed bands, and in particular, pinpoint the band that is responsible for the formation of the three-dimensional Dirac cones. We observe clear evidence of 3D Dirac cones in the three-dimensional momentum space by directly measuring on the k_x–k_y plane and by varying the photon energy to get access to different out-of-plane k_zs. In addition, we reveal new features around the Brillouin zone corners that may be related with surface reconstruction. On the(100) surface, our ARPES measurements over a large momentum space raise an issue on the selection of the basic Brillouin zone in the(100) plane. We directly observe two isolated 3D Dirac nodes on the(100) surface. We observe the signature of the Fermi-arc surface states connecting the two 3D Dirac nodes that extend to a binding energy of ~150 me V before merging into the bulk band. Our observations constitute strong evidence on the existence of the Dirac semimetal state in Na_3Bi that are consistent with previous theoretical and experimental work. In addition, our results provide new information to clarify on the nature of the band that forms the3 D Dirac cones, on the possible formation of surface reconstruction of the(001) surface, and on the issue of basic Brillouin zone selection for the(100) surface.     

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     

Fe—Co双金属催化剂对纳米碳管规模化生产的影响

在C2H2和N2的氛围下,以Fe－Co双金属氧化物为催化剂,利用催化裂解法大量制备了多壁纳米碳管,实验结果表明,以Fe－Co双金属氧化物为催化剂制备纳米碳管的产量明显高于Fe或Co单独存在时所得的纳米碳管的产量,且Fe摩尔分数为0.2时效果最佳;同时发现,在制备的产品中存在很多螺旋形的纳米碳管,此方法工艺简单,有利于纳米碳管的规模化、大批量生产,为纳米碳管的深入研究及广泛应用打下了基础。     

Nanoscale Lasers Based on Carbon Peapods

A scheme of nanoscale lasers based on the so-called carbon peapods is examined in detail. Since there is considerable cylindrical empty space in the middle of a single-wall carbon nanotube （SWCNT）, it can serve as a laser resonant cavity that consists of two highly reflecting alignment ＂mirrors＂ separated by a distance. These mirrors refer to the ordered arrays of C6o inside SWCNTs, which have photonic bandgap structures. Meanwhile, ideally single-mode lasers are supposed to be produced in the nanoscale resonant cavity.