Theoretical characterization of the adsorption configuration of pyrrole on Si(100)surface by x-ray spectroscopy

The possible configurations of pyrrole absorbed on a Si(100)surface have been investigated by x-ray photoelectron spectroscopy(XPS)and near-edge x-ray absorption fine structure(NEXAFS)spectra.The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory(DFT)method and fullcore hole(FCH)approximation to investigate the relationship between the adsorption configurations and the spectra.The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100)surface.Compared with the XPS,the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them.The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments.

Analysis of the injection layer of PTCDA in OLEDs using x-ray photoemission spectroscopy and atomic force microscopy

Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride （PTCDA）/indium-tin-oxide （ITO） thin films using atomic force microscopy, it has been found that the surface is complanate, the growth is uniform and the defects cover basically the surface of ITO. Furthermore, the number of pinholes is small. The analysis of the sample surface and interface further verifies this result by using x-ray photoemission spectroscopy. At the same time, PTCDA is found to have the ability of restraining the diffusion of chemical constituents from ITO to the hole transport layer, which is beneficial to the improvement of the performance and the useful lifetime of the organic light emitting diodes （OLEDs）.

X-ray Photoemission Spectroscopy Studies of the Semiconducting Molybdenum Purple Bronze Bi_(0.2)MoO_3

The electronic structure of the quasi-two-dimensional （2D） semiconducting molybdenum purple bronze Bio.2MoO3 was presented by X-ray photoemission spectroscopy. The valence band of Bio.2MoO3 is made up of Opπ nonbonding level, π and a bonding bands. The peak at 1.5 eV and the shoulder at 0.5 eV in the forbidden band may be formed from the non-bonding dxy orbitals of some Mo atoms. The O1s core-level spectrum demonstrates the presence of two inequivalent bonds of oxygen ions in Bio.2MoO3. Bi4f core-level spectrum shows two bonding characters of Bi atoms in bismuth molybdenum single crystal. Mo3d core-level spectrum confirms two kinds of valence states of Molybdenum （Mo^＋5 and Mo^＋6）. Ar^＋ ion irradiation induces more significant distortion of MoO6 octahedra.

XPS Studies of Magnetic Multilayers

NiOx/Ni81Fe19 and Co/AlOx/Co magnetic multilayers were fabricated by reactive RF/DC magnetron sputtering on clean glass substrates and oxidized Si (100) substrates, respectively. The exchange biasing field (H-ex) between NiO4 and Ni81Fe19 as a function of NiOx oxidation states was studied by X-ray photoelectron spectroscopy (XPS). The oxidation states and the oxide thickness of Al layers in magnetic multilayer films consisting of Co/AlOx/Co were also analyzed. It is found that the H-sr of NiOx/Ni81Fe19 films only depends on Ni2+ but not on Ni3+ or Ni. The bottom Co can be completely covered by depositing an A I layer thicker than 2.0 nm. The oxide layer was Al2O3, and its thickness was 1.15 mn.

XPS Studies of Chemical States of NiO/NiFe Interface

Ta/NTiO/NiFe/Ta multilayers were prepared by radio frequency reactive and dc magnetron sputtering. The exchange coupling field between NiO and NiFe reached 9.6 x 10(3) A/m. The compositions and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique, The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe = Ni + FeO and 3NiO+2Fe =3 Ni+Fe2O3. The thickness of the chemical reaction area estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products appear magnetic defects, and the exchange coupling field H-ex and the coereivity H-c of NiO/NiFe are affected by these defects.

Photoelectric characteristics of silicon P–N junction with nanopillar texture:Analysis of X-ray photoelectron spectroscopy

Silicon nanopillars are fabricated by inductively coupled plasma （ICP） dry etching with the cesium chloride （CsCl） islands as masks originally from self-assembly. Wafers with nanopillar texture or planar surface are subjected to phosphorus （P） diffusion by liquid dopant source （POCl3） at 870 ℃ to form P-N junctions with a depth of 300 nm. The X-ray photoelectron spectroscopy （XPS） is used to measure the Si 2p core levels of P-N junction wafer with nanopillar texture and planar surface. With a visible light excitation, the P-N junction produces a new electric potential for photoelectric characteristic, which causes the Si 2p core level to have a energy shift compared with the spectrum without the visible light. The energy shift of the Si 2p core level is -0.27 eV for the planar P-N junction and -0.18 eV for the nanopillar one. The difference in Si 2p energy shift is due to more space lattice defects and chemical bond breaks for nanopillar compared with the planar one.

Landscape of s-triazine molecule on Si(100) by a theoretical x-ray photoelectron spectroscopy and x-ray absorption near-edge structure spectra study

The chemisorbed structure for an aromatic molecule on a silicon surface plays an important part in promoting the development of organic semiconductor material science. The carbon K-shell x-ray photoelectron spectroscopy（XPS） and the x-ray absorption near-edge structure（XANES） spectra of the interfacial structure of an s-triazine molecule adsorbed on Si（100） surface have been performed by the first principles, and the landscape of the s-triazine molecule on Si（100） surface has been described in detail. Both the XPS and XANES spectra have shown their dependence on different structures for the pristine s-triazine molecule and its several possible adsorbed configurations. By comparison with the XPS spectra, the XANES spectra display the strongest structural dependency of all of the studied systems and thus could be well applied to identify the chemisorbed s-triazine derivatives. The exploration of spectral components originated from non-equivalent carbons in disparate local environments has also been implemented for both the XPS and XANES spectra of s-triazine adsorbed configurations.

XPS and PAT Study on NiAl Phase Formed in a Superalloy by Pack Cementation

The NiAl phase prepared by pack cementation （PC） on a nickel base superalloy was investigated by X-ray photoelectron spectroscopy （XPS） and positron annihilation technique （PAT）. The focus was on the effect of the solid solution of the alloying element from substrate on the binding energy of Ni （Al） 2p peaks and vacancy concentration of the NiAI phase formed in a superalloy. The results showed that the binding energy of Ni 2p peak of the NiAI phase grown in a superalloy was shifted by up to 0.55 eV at the temperature from 850 to 1050℃ towards higher energies and the binding energy of Al 2p peak by up to 1.09 eV in comparison with the NiAl phase formed in pure Ni. The positron lifetimes obtained from the NiAl phase formed in a superalloy were found to be markedly lower than the theoretical values, indicating the decrease in vacancy concentration. The variation of binding energies and vacancy concentration are possibly due to the solid solution of the alloying atoms from the substrate into the NiAI lattice.

Band alignment of p-type oxide/ε-Ga2O3 heterojunctions investigated by x-ray photoelectron spectroscopy

Theε-Ga2O3 p-n heterojunctions(HJ)have been demonstrated using typical p-type oxide semiconductors(NiO or SnO).Theε-Ga2O3 thin film was heteroepitaxial grown by metal organic chemical vapor deposition(MOCVD)with three-step growth method.The polycrystalline SnO and NiO thin films were deposited on theε-Ga2O3 thin film by electron-beam evaporation and thermal oxidation,respectively.The valence band offsets(VBO)were determined by x-ray photoelectron spectroscopy(XPS)to be 2.17 eV at SnO/ε-Ga2O3 and 1.7 eV at NiO/ε-Ga2O3.Considering the bandgaps determined by ultraviolet-visible spectroscopy,the conduction band offsets(CBO)of 0.11 eV at SnO/ε-Ga2O3 and 0.44 eV at NiO/ε-Ga2O3 were obtained.The type-Ⅱband diagrams have been drawn for both p-n HJs.The results are useful to understand the electronic structures at theε-Ga2O3 p-n HJ interface,and design optoelectronic devices based onε-Ga2O3 with novel functionality and improved performance.

Gd-Ni界面的电子结构及其氧化现象

用同步辐射光电发射谱 (SRPES)和XPS研究了室温下Gd膜在Ni(1 1 0 )上的生长和Gd Ni界面的电子结构以及它们的氧化现象 .发现Gd膜在高覆盖度时Gd 4f为双峰结构 ,高温退火使 4f双峰退为单峰 .氧在 3.7nm的Gd膜上的吸附引起Gd 4f双峰中高结合能峰的衰减 ,在 0L～ 5 0L的氧暴露量范围内 ,只存在单一的晶格氧物种 .在轻微氧化的Gd Ni复合薄膜上 ,氧吸附引起Gd向表面的偏析和进一步氧化 ,并存在化学吸附氧 (O-)和晶格氧两种氧物种 .本文对Gd 4f双峰的起源 。

高灵敏度低能离子散射谱在多相催化研究中的应用

多相催化反应大多在催化剂表层发生,研究催化剂的表面组成、结构、化学态和催化性能之间的关系对于设计、优化工业催化剂具有重要意义.高灵敏度低能离子散射谱(HS-LEIS)既可测定样品(包括粉末及块状样品、导体和半导体等)最外原子层的元素组成和相对含量,又可推断催化剂的表面结构,因此被广泛应用于各类催化反应研究中.本文介绍了HS-LEIS的基本原理,并概述了其在催化研究中的一些应用,包括催化剂表面组成、表面活性位、双金属催化剂表面偏析和表面结构、核壳结构等的研究.同时还对比分析了目前在表面研究中应用广泛的X-射线光电子能谱(XPS)和HS-LEIS表征结果的差异,进一步说明HS-LEIS能够更为准确地获得催化剂表面的真实情况.

溅射制备的Al_2O_3薄膜的光学性质

采用中频反应磁控溅射技术,在石英基片上制备了氧化铝薄膜。研究了氧化铝薄膜的XRD谱和Al 2p核心能级的XPS谱随不同制备氧分压比的演变规律。结果表明:随着制备氧分压比的增加,薄膜中的铝元素从金属态逐渐升高到正3价,同时薄膜由晶态逐渐转变成非晶态。当氧分压比为11%时,可以得到符合化学计量比的、非晶态的、表面非常光滑的氧化铝薄膜,该薄膜具有较高的折射率和较低的消光系数。AFM表面相貌图片显示:随氧分压比增加薄膜表面形貌呈现逐渐光滑的趋势。薄膜在300～1100nm波段有很高的透射率。以上性质表明用中频反应磁控溅射技术制备的氧化铝薄膜在光学领域有着广泛的应用前景。

Wet thermal annealing effect on TaN/HfO_2/Ge metal-oxide-semiconductor capacitors with and without a GeO_2 passivation layer

Wet thermal annealing effects on the properties of TaN/HfO2/Ge metal-oxide-semiconductor （MOS） structures with and without a GeO2 passivation layer are investigated. The physical and the electrical properties are characterized by X-ray photoemission spectroscopy, high-resolution transmission electron microscopy, capacitance-voltage （C-V） and current-voltage characteristics. It is demonstrated that wet thermal annealing at relatively higher temperature such as 550 ℃ can lead to Ge incorporation in HfO2 and the partial crystallization of HfO2, which should be responsible for the serious degradation of the electrical characteristics of the TaN/HfO2/Ge MOS capacitors. However, wet thermal annealing at 400 ℃ can decrease the GeOx interlayer thickness at the HfO2/Ge interface, resulting in a significant reduction of the interface states and a smaller effective oxide thickness, along with the introduction of a positive charge in the dielectrics due to the hydrolyzable property of GeOx in the wet ambient. The pre-growth of a thin GeO2 passivation layer can effectively suppress the interface states and improve the C V characteristics for the as-prepared HfO2 gated Ge MOS capacitors, but it also dissembles the benefits of wet thermal annealing to a certain extent.

Annealing temperature dependent catalytic water oxidation activity of iron oxyhydroxide thin films

Nanostructured iron oxyhydroxide（Fe OOH） thin films have been synthesized using an electrodeposition method on a nickel foam（NF） substrate and effect of air annealing temperature on the catalytic performance is studied. The as-deposited and annealed thin films were characterized by X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）, field emission scanning electron microscopy（FE-SEM） and linear sweep voltammetry（LSV） to determine their structural, morphological, compositional and electrochemical properties, respectively. The as-deposited nanostructured amorphous Fe OOH thin film is converted into a polycrystalline Fe;O;with hematite crystal structure at a high temperature. The Fe OOH thin film acts as an efficient electrocatalyst for the oxygen evolution reaction（OER） in an alkaline 1 M KOH electrolyte. The film annealed at 200 °C shows high catalytic activity with an onset overpotential of 240 m V with a smaller Tafel slope of 48 m V/dec. Additionally, it needs an overpotential of 290 mV to the drive the current density of 10 m A/cm;and shows good stability in the 1 M KOH electrolyte solution.

Surface State of Carbon Fibers Modified by Electrochemical Oxidation

Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5% which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

EFFECT OF CERIUM ION IMPLANTATION ON THE AQUEOUS CORROSION BEHAVIOR OF ZIRCONIUM

In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by cerium ions with a dosage range from 1×1016 to 1×1017 ions/cm2 at about 150℃, using MEVVA source at an acceler ative voltage of 40kV. The valence of the surface layer was analyzed by X-ray photo- electron spectroscopy (XPS); Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 0.5mol/L H2SO4 solution. It was found that a remarkable decline in the aqueous corrosion behavior of zirconium implanted with cerium ions compared with that of the as-received zirconium. Finally, the mechanism of the corrosion resistance decline of the cerium-implanted zirconium is discussed.

A nano-scale mirror-like surface of Ti–6Al–4V attained by chemical mechanical polishing

Metal Ti and its alloys have been widely utilized in the fields of aviation, medical science, and micro-electromechanical systems, for its excellent specific strength, resistance to corrosion, and biological compatibility. As the application of Ti moves to the micro or nano scale, however, traditional methods of planarization have shown their short slabs.Thus, we introduce the method of chemical mechanical polishing（CMP） to provide a new way for the nano-scale planarization method of Ti alloys. We obtain a mirror-like surface, whose flatness is of nano-scale, via the CMP method. We test the basic mechanical behavior of Ti–6Al–4V（Ti64） in the CMP process, and optimize the composition of CMP slurry.Furthermore, the possible reactions that may take place in the CMP process have been studied by electrochemical methods combined with x-ray photoelectron spectroscopy（XPS）. An equivalent circuit has been built to interpret the dynamic of oxidation. Finally, a model has been established to explain the synergy of chemical and mechanical effects in the CMP of Ti–6Al–4V.

INFLUENCE OF THE NONMAGNETIC METAL SPACER ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURE OF THE MULTILAYER FILMS

Ta / NiFe/Bi （ Ag, Cu ）/FeMn/Ta and Ta / NiFe1/FeMn / Bi （ Ag, Cu ）/NiFen/Ta films were prepared by magnetic sputtering. The texture and the dependences of the exchange-coupling field on the thickness of Bi, Ag, and Cu in Ta/NiFe/Bi（Ag, Cu） /FeMn/Ta and Ta/NiFe/FeMn/Bi（Ag, Cu）/NiFe/Ta films were studied. XPS results indicate that the Bi atoms migrated into the FeMn layer during the deposition process and a FeMnBi alloy was probably formed or the Bi atoms existed as an impurity in the FeMn layer in Ta/NiFe/Bi（Ag, Cu ）/FeMn/Ta. Otherwise, in Ta/NiFe/FeMn/Bi （Ag, Cu）/NiFe/Ta films, Bi, Ag, and Cu atoms do not remain entirely at the interface of the FeMn/ NiFeⅡfilm, but at least partly segregate to the surface of the NiFe film.

Synthesis and fluorescence properties of cerium-KMgF_3 through a solvothermal process

Phosphor of KMgF3：Ce^3＋ is synthesized through solvothermal method at 180 ℃ and characterized by means of X-ray powder diffraction （XRD） and environment scanning electron microscopy （ESEM）. X-ray photoelectron spectroscopy （XPS） is applied to the study of the energy band structure of KMgF3：Ce^3＋ and confirms the oxygen content of the product is very low. The fluorescence spectra of the rare-earth ion-doped KMgF3 is investigated by the fluorescence spectrophotometer. In the emission spectra, there is a broadband emission with a maximum center located at 306 nm arising from d-f transition of Ce^3＋ in the host. This will be useful for ultraviolet tunable lasers.

Effect of Mo on microstructure,mechanical and corrosion properties of FeCrNiMnMox high-entropy alloys

Four FeCrNiMnMo_(x)(x=0,0.1,0.3,0.5,in molar ratio)high-entropy alloys(HEAs)were synthesized by vacuum arc melting to explore the potential impact of Mo on the microstructure,mechanical properties,and passivation and electrochemical behaviors in 0.5 M H_(2)SO_(4)solution.The results display that the FeCrNiMn alloy exhibits a single face-centered cubic(FCC)structure while the microstructures of the FeCrNiMnMo_(0.1),FeCrNiMnMo_(0.3),and FeCrNiMnMo_(0.5)alloys consist of the FCC andσphase.The appear of theσphase ascribed to the addition of Mo enhances the hardness and yield strength with the sacrifice of plasticity.The FeCrNiMnMox HEAs achieve the maximum hardness of 414 HV_(0.2)and the highest compressive yield strength of 830 MPa when x=0.5,but compressive fracture strain is lowered to 10.8%.X-ray photoelectron spectroscopy(XPS)and electrochemical analysis show that the passivation film in FeCrNiMnMox alloy mainly consists of chromium oxides and molybdenum oxides.Mo has a beneficial effect on the corrosion resistance of the FeCrNiMnMox HEAs in a 0.5 M H_(2)SO_(4)solution by increasing the corrosion potential(E_(corr))and decreasing the corrosion current density(I_(corr))and passivation current density(I_(pass)).The FeCrNiMnMo_(0.1)alloy shows the best corrosion resistance,mainly due to its passivation film consisting of a large proportion of chromium oxide(Cr_(2)O_(3)).More Mo additions promote the formation of the precipitate ofσphase and the matrix regions depleted Cr and Mo elements adverse to the resistance to preferential localized corrosion.