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1.
X-ray Photoelectron Spectroscopy (XPS), Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS) were applied to study the interaction of oxygen molecules with iron films. Supplementarily, iron oxide was investigated for comparison.With XPS from the Fe 2p3/2 range contributions of metallic Fe as well as Fe2+ and Fe3+ can be distinguished. During the interaction with oxygen an oxide film is formed on the iron surface. Nevertheless, XPS still shows metallic contributions even for a surface which is saturated with more than 104 L. The oxide film hinders the dissociation of further impinging oxygen molecules.The interaction of He* atoms with iron oxide surfaces during MIES is dominated by Auger Neutralization. This surprising result follows from the high work function and the fact that intrinsic defects result in a Fermi level pinning to the conduction band. 相似文献
2.
Adsorption and desorption of methanol on a CeO2(1 1 1)/Cu(1 1 1) thin film surface was investigated by XPS and soft X-ray synchrotron radiation PES. Resonance PES was used to determine the occupancy of the Ce 4f states with high sensitivity. Methanol adsorbed at 110 K formed adsorbate multilayers, which were partially desorbed at 140 K. Low temperature desorption was accompanied by formation of chemisorbed methoxy groups. Methanol strongly reduced cerium oxide by forming hydroxyl groups at first, which with increasing temperature was followed by creation of oxygen vacancies in the topmost cerium oxide layer due to water desorption. Dissociative methanol adsorption and creation of oxygen vacancies was observed as a Ce4+ → Ce3+ transition and an increase of the Ce 4f electronic state occupancy. 相似文献
3.
Mixed oxides with large surface area and high thermal stability can be obtained by thermal treatment of the layered double hydroxides (LDH). Mg-Al-Fe mixed oxide samples with varying Mg/Al ratio and 5 mol.% of Fe were prepared in this way and the iron oxidation state (Feox) in these compounds was studied by X-ray photoelectron spectroscopy (XPS), using a calibration based on the relation of Feox to the splitting between the O 1s and Fe 2p3/2 centroids. The XPS results confirm Fe3+ as a dominant oxidation state in the studied mixed oxides. A vacuum-induced reduction of iron in the Fe2O3 and Mg-Al-Fe oxide samples has been observed and an influence of the Mg:Al ratio on this effect in mixed oxides has been detected. The role of the local variations of the electron density distribution in the close neighbourhood of the surface oxygen atoms in the mixed oxides in the reduction processes is discussed. 相似文献
4.
S. P tigny H. Most fa-Sba B. Domenichini E. Lesniewska A. Steinbrunn S. Bourgeois 《Surface science》1998,410(2-3):250-257
Compositional and chemical changes of titanium dioxide monocrystalline surfaces induced by bombardment with 4 keV argon and oxygen ions have been studied by AES, XPS and AFM. Argon ion bombardment induced strong changes in the composition and chemical state of the surface: loss of oxygen due to preferential sputtering occurred, and, related to this, Ti4+ species were reduced to Ti3+ and Ti2+. During oxygen bombardment, competition between preferential sputtering of oxygen ions of the oxide surface and oxygen implantation was observed. This phenomenon was found to be strongly dependent upon the incidence angle of the oxygen ions. Moreover, an oxygen bombardment with normal incidence of the surface that had been previously submitted to an argon ion bombardment led to a restoichiometrization of the surface: no further Ti3+ or Ti2+ was found by XPS, only Ti4+. 相似文献
5.
P. GhodsO.B. Isgor J.R. BrownF. Bensebaa D. Kingston 《Applied Surface Science》2011,257(10):4669-4677
X-ray photoelectron spectroscopy (XPS) was used to study the properties of passive oxide film that form on carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties. The thickness of the oxide films was determined to be approximately 4 nm and was not affected by the exposure time. Near the film/substrate interface the concentration of the Fe2+ oxides was higher than the concentration of the Fe3+ oxides; the layers near the free surface of the film mostly contained Fe3+ oxides. Chloride exposure decreased the thickness of the oxide films and changed their stoichiometry such that near the film/substrate interface Fe3+/Fe2+ ratio increased. 相似文献
6.
J.K. Gimzewski B.D. Padalia S. Affrossman L.M. Watson D.J. Fabian 《Surface science》1977,62(2):386-396
Adsorption of oxygen on iron at ambient temperature and low pressure is shown by XPS to give a chemisorbed species and the oxide, Fe2O3. At low temperatures a further adsorbed species is detected, similar to the nickel-oxygen system. Correction of the intensity of the oxygen signal for depth results in an oxidation curve in agreement with reported work using other techniques, i.e. oxidation is fast until about four layers of oxide are formed, at an exposure of ca. 102 L, and then proceeds slowly to about ten layers. Adsorption of water vapour produces an overlayer less than one layer in depth at an exposure of 105 L. Comparison of the overlayer depths calculated from the decrease in unoxidised iron signal intensity and from the increase in oxygen intensity gives good agreement for the thick oxide film produced by oxygen adsorption, but not for the thin overlayer formed by exposure to water vapour. This suggests a difference in packing of the ions in the thin overlayer compared to the arrangement in the bulk oxide. 相似文献
7.
The frequency-dependent properties of Mn-doped (3-5 at.%) aligned zinc oxide (Mn-ZnO) nanorods, synthesized by hybrid wet chemical route onto glass substrates, were investigated by bias-dependent impedance spectroscopy. No peak of Mn cluster/secondary phases was detected in the X-ray diffraction traces of the samples. XPS studies show the presence of oxygen vacancies in Mn-ZnO nanorods and Mn in Mn2+ and Mn4+ charge states. Although X-ray diffraction/X-ray photoelectron spectroscopy does not give any indication of the presence of metal clusters in the samples, bias-dependent impedance spectroscopy demonstrates significant sensitivity to the formation of Mn clusters in Mn-ZnO nanorods. 相似文献
8.
M. A. Korotin A. O. Anokhin I. S. Zhidkov A. I. Kukharenko S. O. Cholakh N. V. Gavrilov V. I. Brinzari E. Z. Kurmaev 《JETP Letters》2018,108(8):537-542
X-ray photoelectron spectroscopy and electronic structure calculations in the framework of the coherent potential approach show that impurity Fe3+ ions substituting In in iron-doped In2O3 indium oxide(III) are in a paramagnetic state in the absence of oxygen vacancies. 相似文献
9.
V. M. Zainullina M. A. Korotin V. L. Kozhevnikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):425-431
The electronic structure of strontium ferrite Sr3Fe2O6 was
calculated using the tight-binding linear muffin-tin orbital method (TB
LMTO) in the local spin density approximation of density functional theory
with Coulomb correlations correction (LSDA+U). The semiconducting character
of the spectrum with charge transfer energy gap of 1.82 eV was obtained in
reasonably good agreement with experimental data. The iron ions are found
to be in the high spin state. The calculated value of the local spin
magnetic moment of Fe3+ ion is 3.94 μB which is not typical for
trivalent iron ion in the high spin state. It is shown that the strong
hybridization between Fe3d and O2p orbitals favors the
d6 L configuration of Fe3+ ion, where L is a hole in the oxygen p shell. The mechanism of oxygen transport in ferrite is discussed basing on the total energy calculations of the
different spatial configurations of oxygen vacancies. 相似文献
10.
Weixin Huang 《Surface science》2006,600(4):793-802
The interaction of atomic hydrogen with thin epitaxial FeO(1 1 1) and Fe3O4(1 1 1) films was studied by TDS, XPS and LEED. On the thin, one Fe-O bilayer thick FeO film, partial reduction occurs in two steps during exposure. It ends after removal of 1/4 monolayer (ML) of oxygen with a 2 × 2 pattern appearing in LEED. This FeO0.75 film is passive against further reduction. The first reduction step saturates after removal of ∼0.2 ML and shows autocatalytic kinetics with the oxygen vacancies formed during reduction causing acceleration. The second step is also autocatalytic and is related with reduction to the final composition and an improvement of the 2 × 2 order. A structure model explaining the two-step reduction is proposed. On the thick Fe3O4 film, irregular desorption bursts of H2O and H2 were observed during exposure. Their occurrence appears to depend on the film quality and thus on surface order. Because of the healing of reduction-induced oxygen vacancies by exchange of oxygen or iron with the bulk, a change of the surface composition was not visible. The existence of partially reduced oxide phases resistant even to atomic hydrogen is relevant to the mechanism of dehydrogenation reactions using iron oxides as catalysts. 相似文献
11.
为了研究阻变存储器导电细丝的形成位置和分布规律, 使用X射线光电子能谱研究了Ti/HfO2/Pt阻变存储器件单元中Hf 4f的空间分布, 得到了阻变层的微结构信息. 通过I-V测试, 得到该器件单元具有典型的阻变特性; 通过针对Hf 4f的不同深度测试, 发现处于低阻态时, 随着深度的增加, Hf4+化学组分单调地减小; 而处于高阻态和未施加电压前, 该组分呈现波动分布; 通过Hf4+在高阻态和低阻态下组分含量以及电子能损失谱分析, 得到高阻态下Hf4+组分的平均含量要高于低阻态; 另外, 高阻态和低阻态下的O 1s谱随深度的演变也验证了Hf4+的变化规律. 根据实验结果, 提出了局域分布的氧空位聚簇可能是造成这一现象的原因. 空位簇间的链接和断裂决定了导电细丝的形成和消失. 由于导电细丝容易在氧空位缺陷聚簇的地方首先形成, 这一研究为导电细丝的发生位置提供了参考. 相似文献
12.
M. A. Melkozerova O. I. Gyrdasova T. V. D’yachkova A. P. Tyutyunnik V. V. Bannikov E. V. Zabolotskaya V. V. Marchenkov Yu. A. Perevozchikova F. Sauerzopf V. N. Krasil’nikov 《Physics of the Solid State》2017,59(8):1506-1511
Single-phase polycrystalline samples of Zn0.95Fe0.05O having the wurtzite structure and different morphology of particles were obtained using precursor technologies. It was found by electron spin resonance that iron enters the ZnO crystal lattice in the Fe3+ charge state. Magnetic studies revealed that the obtained samples show weak ferromagnetic properties at 300 K. A correlation between the number of oxygen vacancies and the degree of ferromagnetic ordering was found. 相似文献
13.
A microscopic model for the surface parameter in thin YIG films is proposed to explain the observed properties of the non-propagating surface spin-wave. This theory proposes two surface interactions. The first is a temperature dependent molecular field coupling between the surface iron atoms and the gadolinium atoms at the film substrate interface. The second interaction is a single ion anisotropy due to Fe2+ ions present at the surface resulting from the migration of oxygen vacancies during annealing. Excellent agreement is observed between the experimental results and the prediction of the microscopic theory. 相似文献
14.
A. G. Goncharov L. P. Nikitina 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(2):284-290
The chemical composition of mineral associations in the rock of mantle xenoliths was investigated, the content of Fe2+ and Fe3+ being determined by the M?ssbauer spectroscopy technique. The crystallization conditions (temperature, pressure, and oxygen
fugacity) of mantle xenoliths and the composition of the coexisting mantle fluids were assessed. The dependence of the iron
oxidation state in spinels on the fugacity of oxygen in a particular system was determined. 相似文献
15.
Takahiro Hiramatsu Mamoru FurutaTokiyoshi Matsuda Chaoyang LiTakashi Hirao 《Applied Surface Science》2011,257(13):5480-5483
Behavior of oxygen in sputtering deposited ZnO films through thermal annealing and its effect on sheet resistance of the films were investigated. The crystallinities of the ZnO film were improved by post-deposition annealing in vacuum. However, the sheet resistance of ZnO film was dramatically decreased after post-deposition annealing in vacuum at more than 300 °C, while O2 desorbed from the film. The oxygen vacancies which acted as donors were formed by the thermal annealing in vacuum. The sheet resistance of the films was recovered by annealing in oxygen ambient. In this paper, 18O2 gas as an oxygen isotope was used as the annealing ambient in order to distinguish from 16O, which was constituent atom of the ZnO films. SIMS analysis revealed that 18O diffused into the ZnO film from the top surface by 18O2 annealing. Therefore oxygen vacancies formed by the post-deposition annealing in vacuum could be compensated by the annealing in oxygen ambient. 相似文献
16.
采用磁控溅射工艺制备了V2O5薄膜.通过改变制备工艺中基片温度和氧分压两个条件,研究了薄膜的晶相组成、表观形貌以及氧化物中钒和氧元素的化合价态.当基片温度升高时,V2O5薄膜中颗粒结晶由细长针状转变为平行于基片的片状,V5+状态保持不变,但723 K时氧结合能向高键能态移动.氧分压较低时,薄膜表面有部分V4+态存在,但存在较多的高键能氧,此时薄膜中晶粒尺寸较小.随着氧分压的提
关键词:
氧化钒
磁控溅射
相变薄膜
X射线光电子能谱 相似文献
17.
M. Salou B. Lescop S. Rioual A. Lebon J. Ben Youssef B. Rouvellou 《Surface science》2008,602(17):2901-2906
X-ray photoelectron spectroscopy (XPS) and work-function measurements were used in combination to investigate the initial steps of Permalloy (Ni80Fe20) oxidation at room temperature. They showed that, after oxygen saturation, the surface is covered by nickel oxide (NiO), nickel hydroxide (Ni(OH)2) and iron oxides (FexOy), and there is no preferential oxidation. Iron oxidation proceeds through the formation of FeO (Fe2+) followed with Fe2O3 growth (Fe3+). The oxidation is governed by a dissociative Langmuir-type oxidation: the sticking coefficient is decreasing over oxygen exposure. Oxidation continues by oxygen dissolution into the first layers to form a nano-oxide of about 8 Å in thickness. 相似文献
18.
Z.H. Zhang X.L. Zhong H. Liao F. Wang J.B. Wang Y.C. Zhou 《Applied Surface Science》2011,257(17):7461-7465
In the present work, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition depth profiles of Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film, which was prepared on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by chemical solution deposition (CSD). It is shown that there are three distinct regions formed in BNT film, which are surface layer, bulk film and interface layer. The surface of film is found to consist of one outermost Bi-rich region. High resolution spectra of the O 1s peak in the surface can be decomposed into two components of metallic oxide oxygen and surface adsorbed oxygen. The distribution of component elements is nearly uniform within the bulk film. In the bulk film, high resolution XPS spectra of O 1s, Bi 4f, Nd 3d, Ti 2p are in agreement with the element chemical states of the BNT system. The interfacial layer is formed through the interdiffusion between the BNT film and Pt electrode. In addition, the Ar+-ion sputtering changes lots of Bi3+ ions into Bi0 due to weak Bi-O bond and high etching energy. 相似文献
19.
20.
Charge transport and bipolar switching mechanism in a Cu/HfO_2/Pt resistive switching cell
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Bipolar resistance switching characteristics are investigated in Cu/sputtered-HfO_2/Pt structure in the application of resistive random access memory(RRAM).The conduction mechanism of the structure is characterized to be SCLC conduction.The dependence of resistances in both high resistance state(HRS) and low resistance state(LRS) on the temperature and device area are studied.Then,the composition and chemical bonding state of Cu and Hf at Cu/HfO_2 interface region are analyzed by x-ray photoelectron spectroscopy(XPS).Combining the electrical characteristics and the chemical structure at the interface,a model for the resistive switching effect in Cu/HfO_2/Pt stack is proposed.According to this model,the generation and recovery of oxygen vacancies in the HfO_2 film are responsible for the resistance change. 相似文献