共查询到20条相似文献,搜索用时 78 毫秒
1.
M. Knupfer K. Widder M. Sing O. Knauff J. Fink 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):323-328
We have measured the dispersion of plasmon excitations in polycrystalline Sn, Pb, Cd and Zn using electron energy-loss spectroscopy
(EELS) in transmission. These metals show a remarkable deviation of their plasmon behaviour from standard theoretical expectations
which can be attributed to the presence of shallow core levels in the energetic neighborhood of the plasmon energy. The position
of the plasmon resonance in the long wavelength limit is in line with predictions from model assumptions taking into account
the core level polarization effects. We show that not only the plasmon energy in the optical limit but also the plasmon dispersion
is altered by the interaction of the charge carrier plasmon and the core level excitations.
Received: 15 June 1998 / Revised and Accepted: 9 July 1998 相似文献
2.
Initial oxidation process of Mg films was investigated by Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS). A polycrystalline Mg film was exposed to oxygen at room temperature. An inspection of EELS reveals that the initial oxidation process could be classified according to the curve profile in the low energy loss region. The oxide formation is initiated after oxygen exposure of 3 L (Langmuir). 相似文献
3.
We report on the investigation of composition fluctuations in epitaxially grown (Ga,In)(N,As) epilayers on GaAs(001) substrates by using electron energy-loss spectroscopy (EELS). The N and In concentrations are determined locally with a probe size of about 8 nm from the low-loss EELS measurements. We demonstrate that the small amount of N incorporating in dilute nitride alloys can be measured quantitatively by the plasmon energy shift with respect to a GaAs reference, and that the In content is analyzed simultaneously from the In 4d transitions, which have been isolated from the overlapping Ga 3d transitions. Our spatially resolved EELS results are utilized to discuss the origin of the inherent composition fluctuations and their influences on the morphological instabilities during epitaxial growth. 相似文献
4.
利用低能电子衍射(LEED)、X射线光电子能谱(XPS)、电子能量损失谱(EELS)、紫外光电子能谱(UPS),对室温下Mn在GaAs(100)4×1表面的淀积过程进行了研究。研究结果表明,当锰的覆盖度θ≥0.25nm时,LEED图案完全消失,表明Mn没有生长成单晶。LEED,EELS的结果都表明淀积初期是层状生长的。对XPS的Ga2p3/2,As2p3/2的峰形、强度进行分析,可以知道在很小的覆盖度下,Mn就与衬底反应。置换出的Ga被局限在离原来的界面约3nm
关键词: 相似文献
5.
6.
The deposition of silver on an ordered alumina film prepared on Re(0001) surface has been studied by Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and high resolution electron energy loss spectroscopy (HREELS). The results show that Ag grows initially as clusters at 90K and 300K. A red shift of the Ag surface plasmon as a function of decreasing coverage is observed, which is related to the cluster size effect. A surface plasmon characteristic of metallic Ag appears at coverages higher than 2.8 monolayer equivalent. 相似文献
7.
Marisa Scrocco 《Journal of Electron Spectroscopy and Related Phenomena》1992,60(4):363-373
Specific information on the energy level diagram and on the energy forbidden gap of tetraphenylporphyrin and its Ni derivative has been obtained by means of electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy techniques. Comparison of the free ligand and its metal derivative emphasizes the importance of the metal 3d levels in the conduction processes. The interband and plasmon transition present in the EELS spectra of these species are compared with the theoretically calculated energy level diagram and experimental data. 相似文献
8.
H. Hövel 《Applied Physics A: Materials Science & Processing》2001,72(3):295-302
With controlled growth in nanometer-sized pits we produced silver and gold clusters on a graphite surface. We give a summary
of the preparation method and discuss the scanning tunneling imaging and the crystalline orientation of the clusters. The
electronic structure of the clusters was studied by an in-situ combination of ultraviolet photoelectron spectroscopy (UPS)
and scanning tunneling spectroscopy (STS). For both techniques we obtained an energy resolution in the range of 10 meV employing
low sample temperatures. Dynamic final-state effects together with averaging over a cluster-size distribution result in characteristic
spectral shapes in UPS, which can be understood referring to STS data taken on individual clusters. Finally, directions for
future experiments are pointed out.
Received: 13 April 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
9.
Highly oriented pyrolytic graphite (HOPG) as well as polycrystalline graphite (pc-graphite) were bombarded with 3.5 keV H+ ions by means of a Penning ion source. The implanted graphite was characterized by in situ electron spectroscopy techniques such as UPS, XPS and EELS. Our UPS valence band measurements of the hydrogen saturated graphite reveal it to be an insulating phase, and XPS measurements show a shift of the C1s core level to higher binding energy with respect to pristine graphite. This behavior is explained by a Fermi energy shift upon hydrogen bombardment of graphite.In addition, a close resemblance in the electronic structure of hydrogen bombarded graphite and amorphous hydrogenated carbon films (a-C:H) is shown which suggests the modification of pristine graphite to an amorphous network [1] of mostly tetrahedrally bonded carbon atoms by hydrogen implantation. 相似文献
10.
本文用X射线光电子能谱(XPS),紫外光电子能谱(UPS),电子能量损失谱(EELS)和低能电子衍射(LEED)研究了O与预覆盖K的Ag(110)表面相互作用及其性质。在低覆盖度K下,发现有两种O的吸附态,经鉴别为溶解到表面下的O2-和表面上吸附的Ox-增加K的覆盖度,出现分子状态的吸附物O2δ-,它与表面下存在的K相联系。XPS和UPS均清楚地显示出对应于三种不同吸附态的光电子发射峰。Ag(110)表面预覆盖K后的粘滞系数大大增加。K和O的共吸附引起它们彼此向Ag(110)表面下的溶解。LEED实验结果表明,清洁Ag(110)表面覆盖单层K原子后衍射图形从(1×1)变到(1×2),再吸附O后表面吸附层结构变为(2×1)。另外,结合UPS和EELS测量初步考察了O/K/Ag(110)共吸附系统的电子结构。本文还提出了一个共吸附模型来解释这些现象。
关键词: 相似文献
11.
L.S. Wang D.B. Buchholz Y. Li J. Li C.Y. Lee H.T. Chiu R.P.H. Chang 《Applied Physics A: Materials Science & Processing》2007,87(1):1-6
A method for the fabrication of large quantities of high quality silver nanocables encapsulated in carbon nanotubes (Ag@C)
using a hydrogen arc is presented. A growth mechanism based on the generation of poly-aromatic hydrocarbons by the hydrogen
arc is proposed. The size-dependent electronic structures of the resultant materials are investigated using electron energy
loss spectroscopy (EELS). The surface plasmon and bulk-excitation character observed by EELS are discussed. As the diameter
of Ag@C nanocable decreases, the surface and bulk plasmons of the silver core shift to lower energy and the peaks broaden.
Measurements of electrical conductivity exhibits a liner current–voltage character with a conductivity of 0.5×104 S/cm for the nanocable structure.
PACS 81.05.Tp; 81.07.-b 相似文献
12.
In this paper a number of experimental results dealing with the study of the electronic properties of H-exposed III–V semiconductor cleavage surfaces will be reviewed. The principal aim of the paper is to show how surface sensitive spectroscopies like electron energy loss spectroscopy (EELS) and ultraviolet photoemission spectroscopy (UPS) can be used to investigate these systems. The paper is focused on GaAs(1 1 0):H. GaAs(1 1 0) is one of the most widely investigated and better known semiconductor surfaces: this system can be taken as a case study for the interaction of H with III–V semiconductor cleavage surfaces. The paper is divided into two parts. In the first part EELS and UPS are used and combined to get information about the surface valence states. In the second part core level (CL) photoemission results are presented and discussed.
Combining theory with the above results, a unified picture of the H interaction with the (1 1 0) surface of GaAs comes out. H atoms chemisorb at the early stages along the dangling bond directions of the ideal not relaxed surface, removing the surface relaxation and introducing at the same time defects at the surface.
At the same time the interaction with H produces a Ga enrichment at the surface ascribed to As desorption. 相似文献
13.
T. Grenet M.C. Cheynet 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):701-705
We present the results of an electron energy loss spectroscopy (EELS) investigation of the icosahedral quasicrystals i-Al-Cu-Fe,
i-Al-Pd-Mn and i-Al-Pd-Re. The spectra of the three systems studied are very similar. Their main contribution comes from a
broad plasmon like peak, which can be interpreted as an “s-p" electron plasmon damped by “d" electron interband transitions. We show that it is similar to those found in other simple crystalline aluminum-transition
metal alloys, so that no specificity related to the quasicrystalline order of the alloys dominates.
Received 3 November 1998 and Received in final form 16 July 1999 相似文献
14.
Y. Jugnet J.C. Bertolini J. Massardier B. Tardy Tran Minh Duc J.C. Vedrine 《Surface science》1981,107(1):L320-L328
CO adsorption on the (111) face of a Pt10Ni90 alloy single crystal has been investigated at room temperature by vibrational electron energy loss spectroscopy (EELS) and photoelectron spectroscopy (XPS and UPS). Two well separated CO stretching modes develop at 2070 and 1820 ± 10 cm?1, with their intensities reaching 64 and 36% respectively of the total intensity at saturation coverage. They are attributed to CO adspecies in terminal and bridge bonded configuration respectively. The UPS spectra of 4σ, 5σ and 1π molecular orbitais of adsorbed CO show complex features which may be resolved into two components having the main characteristics of CO adsorbed on pure Pt(111) and Ni(111) respectively. Such behaviour is also observed by XPS on C 1s on O 1s peaks. Their respective contributions, in both XPS and UPS spectra are about 64 and 36% of the whole spectrum. Finally compared to Ni(111) — on which CO adsorbs mainly in bridge configuration — the alloying with 10% Pt has generated the appearance of a large number of new sites for CO chemisorption associated with the presence of Pt atoms at the surface. The large amount of terminal CO adspecies is interpreted in terms of considerable surface enrichment of the alloy in platinum. 相似文献
15.
Dung T. Tran Ian P. Jones Jon A. Preece Roy L. Johnston Coenraad R. van den Brom 《Journal of nanoparticle research》2011,13(9):4229-4237
Dodecanethiol-capped Cu–Au nanoparticles, synthesized via a successive two-phase (water/toluene) and galvanic-exchange procedure,
were characterized using transmission electron microscopy (TEM). The size range of the particles is around 1–7 nm. Electron-induced
morphological evolution was observed under high resolution (HR) TEM. Cuboctahedral morphology was found to be thermodynamically
stable. Electron-induced aggregation of two particles was also observed. Chemical ordering of cuboctahedral particles was
studied by atomic-resolution high angle annular dark field (HAADF) imaging in scanning TEM (STEM) mode and energy dispersive
X-ray (EDX) element mapping using a silicon drift detector (SDD). The particles were found to be Cu–Au mixed, and to be stable
in air. Surface plasmon resonance (SPR), which is dependent on local structure and morphology, was investigated by electron
energy loss spectroscopy (EELS). 相似文献
16.
Electron energy loss spectroscopy (EELS) on plasmons has been applied to determine the thermal expansion coefficient on the surface and to estimate the density of conduction electrons in the surface layer of aluminium. Using the data on the temperature dependence of the surface plasmon energy shift, the value of thermal expansion coefficient on the surface was calculated to be αs=1.3 × 10?4K?1 that is about two times higher than the bulk value. A simple model is proposed which takes account of the influence of electron density non-uniformity in the surface layer on the dispersion of plasma oscillations. An estimation of the density of conduction electrons in the surface layer based on the observed dependence of the surface plasmon energy on the energy of primary electrons gave a value about 5% lower than the bulk value. The thickness of altered surface layer is about 10 Å. 相似文献
17.
S. A. Nepijko D. N. Ievlev W. Schulze 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):115-117
The plasmon energy of Ag clusters produced on an amorphous
carbon substrate by gas-aggregation technique has been measured.
It has been determined from the plasmon peak position in the
light emission spectrum obtained during bombardment of Ag
clusters by low-energy electrons. For Ag cluster films with
maximum of the cluster size distribution at 30, 8 and 2.5 nm,
the plasmon energy comprised 3.76, 4.13 and 4.28 eV (the
wavelength was 330, 300 and 290 nm), respectively. The blue
shift of the plasmon energy is probably related to the effect of
confounding of collective and single-particle excitations. 相似文献
18.
The adsorption of methyl chloride on a Pd(100) surface has been investigated by ultraviolet photoelectron spectroscopy (UPS), electron energy loss spectroscopy (in the electronic range, EELS), temperature-programmed desorption (TPD) and work function change. CH3Cl adsorbs with high sticking probability at 80–100 K. UPS and TDS spectra suggest that the adsorption of CH3Cl is molecular at 100 K, with a little distortion of the corresponding gas-phase molecular electronic structure. No dissociation of CH3Cl was observed even up to 550 K. By means of TPD, we distinguished two adsorption states with desorption energies of 46.9 and 33.4 kJ/mol. The formation of a condensed layer at 105–110 K was also observed. Adsorption of CH3Cl caused a significant work function decrease, Δ = −0.91 eV, indicating a dipole with positive end pointed away from the surface. The effects of electronegative additives, preadsorbed Cl and O were also examined. Preadsorbed Cl caused a slight destabilization of adsorbed CH3Cl at lower concentration, prevented the adsorption of CH3Cl at higher concentration and facilitated the formation of a condensed layer. No such effect was experienced in the presence of preadsorbed O. 相似文献
19.
High energy electron energy loss spectroscopy (EELS) has been used to study the influence of the intercalation with pyridine on the optical properties of the host material 2H-NbS2. The optical joint density of states function OJDOS(ω) of the intercalated material is found to be well represented by a linear superposition of the OJDOS of pure NbS2 and that of pyridine. A charge transfer from pyridine to NbS2 of (0.27±0.05) electrons per NbS2 formula unit is deduced from the energy shift of the d-band plasmon loss relative to the pure host material. Assuming this shift to be caused by a change in the charge density contributing to the d-band plasmon is confirmed by an unchanged effective mass of the electrons in the dz2 band upon intercalation as has been deduced from the dispersion of the plasmon in question. 相似文献
20.
Nanostructures in the form of nanowires or filled nanotubes and nanoparticles covered by shells are of great interest in materials science. They allow the creation of new materials with tailored new properties. For the characterisation of these structures and their shells by means of analytical transmission electron microscopy (TEM), especially by energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS), the accurate analysis of linescan intensity profiles is necessary. A mathematical model is described, which is suitable for this analysis. It considers the finite electron beam size, the beam convergence, and the beam broadening within the specimen. It is shown that the beam size influences the measured result of core radius and shell thickness. On the other hand, the influence of the beam broadening within the specimen is negligible. At EELS, the specimen thickness must be smaller than the mean free path for inelastic scattering. Otherwise, artifacts of the signal profile of a nanowire can pretend a nanotube. 相似文献