Probing the Roughness of Porphyrin Thin Films with X-ray Photoelectron Spectroscopy

Thin-film growth of molecular systems is of interest for many applications, such as for instance organic electronics. In this study, we demonstrate how X-ray photoelectron spectroscopy (XPS) can be used to study the growth behavior of such molecular systems. In XPS, coverages are often calculated assuming a uniform thickness across a surface. This results in an error for rough films, and the magnitude of this error depends on the kinetic energy of the photoelectrons analyzed. We have used this kinetic-energy dependency to estimate the roughnesses of thin porphyrin films grown on rutile TiO₂(110). We used two different molecules: cobalt (II) monocarboxyphenyl-10,15,20-triphenylporphyrin (CoMCTPP), with carboxylic-acid anchor groups, and cobalt (II) tetraphenylporphyrin (CoTPP), without anchor groups. We find CoMCTPP to grow as rough films at room temperature across the studied coverage range, whereas for CoTPP the first two layers remain smooth and even; depositing additional CoTPP results in rough films. Although, XPS is not a common technique for measuring roughness, it is fast and provides information of both roughness and thickness in one measurement.     

一些钼络合物的X光电子能谱

本文研究了一些钼络合物的X光电子能谱,测定了钼3d电子的结合能(E_b),并讨论了钼的氧化态和桥连原子对此的影响。     

自组装成膜技术制备TiO2薄膜的XPS研究

采用自组装成膜技术制备里TiO2薄膜,应用X射线光电子能谱研究自组装膜及其氧化膜和淀积的TiO2薄膜，结果表明，硅烷偶联剂成功地组装在玻璃基片上，足够长时间的氧化对使端基（-SH）完全氧化为磺酸基，淀积在基片上的TiO2膜牢固性好，平均膜厚在10nm．淀积膜中的钛可能有几种不同的氧化态，不同的酸度影响TiO2的淀积效果     

The Nature of the Azonium Cation as Evidenced by X-Ray Photoelectron Spectroscopy

The question of the classical or non-classical nature of aryl-substituted azonium cations as well as of the pyridazinium cation has been settled by X-ray photoelectron spectroscopy in favour of the classical structure. The relative magnitude of the observed N1s binding energies is reasonably well reproduced on the basis of the theoretically calculated charge structure of these ions. The relative magnitude of the crucial intramolecular potential terms, appearing in the theoretical treatment, is also suggested from PMR.-investigations on protonated azo-compounds. The electronic structure of these species is compared with that implied by commonly accepted classical valence structures and parallels to carbo-cations are drawn. MINDO/2 calculations of the proton affinities of azo-compounds, considering structurally different conjugate acids, also support a classical azonium cation structure. The gas phase basicity of azobenzene is predicted to be higher than that of azomethane.     

Thin Films of Molecular Metals TTF-TCNQ

We present recent results on the characterization of highly ordered polycrystalline thin films of the charge transfer salt TTF-TCNQ (TTF=tetrathiafulvalene, TCNQ=tetracyanoquinodimethane) prepared by thermal sublimation in high vacuum under different conditions. The increase in orientation and microcrystal size as a function of substrate and annealing temperatures is addressed. A consequence of such an increase is the reduction of the conductivity activation energy, which eventually leads to the observation of the Peierls transition by resistivity measurements. X-ray absorption near edge spectroscopy studies performed with synchrotron radiation reveal directly the influence of charge transfer on unoccupied states near the Fermi level.     

Composition Profiles of Dental Enamel Studied by X-Ray Photoelectron Spectroscopy (ESCA)

Abstract

The surfaces of both normal and fluoride treated human dental enamel were examined with x-ray photoelectron spectroscopy (ESCA). Using argon-ion etching to remove thin layers of enamel, subsurface layers were also analyzed. The resulting composition-depth profile showed that stannous fluoride produced a subsurface layer containing both tin and fluoride whereas fluorine was absent from the surface layer. Acid fluoride treatments, however, converted the surface to calcium fluoride which steadily decreased in concentration with depth.     

Effect of Radiation Defects on the Electronic Structure of Zircon by X-Ray Photoelectron Spectroscopy Data

X-Ray photoelectron spectroscopy (XPS) is used to study the electronic structure of radiation damaged samples of ZrSiO₄ zircon mineral at early and middle stages of its radiation destruction. The effects of radiation induced atomic disordering are found to be most distinctly manifested in the spectra of O1s states and to a smaller extent in the spectra of Si2p states, and also in the zircon valence band. Based on the quantum chemical calculation results the conclusion is drawn that the observed changes in XPS lines are caused by the formation of oxygen vacancy defects and an increase in the covalency of interatomic bonds near oxygen vacancies. For zircon samples with a low/moderate degree of radiation damage these changes reflect the initial stage of the polymerization of the ZrSiO₄ structure due to the formation of Si—O—Si chain fragments.     

Chiral Thin Films of Metal Oxide

In this paper, we describe for the first time the synthesis of new chiral nanosized metal oxide surfaces based on chiral self‐assembled monolayers (SAMs) coated with metal oxide (TiO₂) nanolayers. In this new type of nanosize chiral surface, the metal oxide nanolayers enable the protection of the chiral self‐assembled monolayers while preserving their enantioselective nature. The chiral nature of the SAM/TiO₂ films was characterized by variety of unique techniques, such as second‐harmonic generation circular dichroism (SHG‐CD), quartz crystal microbalance, and chiral adsorption measurements with circular dichroism spectroscopy. The chiral resolution abilities of the SAMs coated with metal oxide (TiO₂) nanolayers were investigated in the crystallization of a racemic mixture of threonine and glutamic acid. Our proposed methodology for the preparation of nanoscale chiral surfaces described in this article could open up opportunities in other fields of chemistry, such as chiral catalysis.     

XPS对多层膜中单层膜厚的测定

依据XPS的测量信号与能量损失有一定定量关系的原理,利用数理分析方法,推导数学模型进行多层膜中单层膜厚的计算,该方法是一种测量总膜厚小于10nm的单层膜厚的非破坏性的方法,具有较高的准确性。     

钌—钛金属氧化物涂层电极的电子能谱分析

用X-光电子能谱分析了Ru-Ti金属氧化物电极的组成、结构和元素价态。结果表明,电极表面不同于体内,讨论了表面和体内Ti的价态区别对Ru-Ti阳极活性和寿命的影响,指出掺杂Ir和Pd后会提高电极活性。     

X-Ray Microanalysis of Thin Surface Films and Coatings

 The paper gives an overview of the present knowledge in the field of X-ray analysis of surface films and more generally stratified specimens. The aim of the paper is not to report the details and formulas of the available quantitative procedures, but to concentrate on the general ideas and orders of magnitude illustrating the capability and limits of the method, and on the optimal adaptation of the operating conditions to every particular problem. The various specific pitfalls which can be encountered are pointed out, in particular the fluorescence effects when using high-energy X-ray lines, or the anomalies due to chemical bonding, absorption uncertainties, and contamination effects when soft radiations are employed.     

X-Ray and X-ray Photoelectron Spectroscopy Studies of the Electronic Structure of Borane Derivatives

This paper reviews the results of electronic structure studies of a number of typical members of borane series by X-ray and X-ray photoelectron spectroscopy using quantum chemical calculations. Fragment analysis of the molecular orbital structure is given. The nature of chemical interaction in boron cluster compounds is studied on models: simple molecules NH₃, BH₃, and BF₃ and their adducts NH₃BH₃ and NH₃BF₃. The electronic structure of B₁₀H₁₂L₂ type compounds with Lewis bases L = NH₃, (CH₃)₂S, (C₆H₅)₃P is analyzed. The complexes are considered in terms of the concept of donor–acceptor interactions between the fragments. The donor–acceptor bond has contributions from both occupied and vacant acceptor orbitals. X-ray photoelectron data on the charged states of atoms in the compounds are overviewed. Electron distribution in complex compounds with transition metals [(1,2-B₉C₂H₁₁)₂M]^–, M = Fe^III, Co^III, Ni^III, and Ni^IV and chain type polycobaltocarborane anions {[(3)-1,2-B₉C₂H₁₁]₂Co _n [(3,6)-1,2-B₈C₂H₁₀]_n-1} ^n– , n = 2-7, is considered.     

氩离子刻蚀还原氧化铜的XPS研究

利用X射线光电子能谱(XPS)及氩离子刻蚀技术,通过改变氩离子枪的刻蚀模式,原位研究氩离子刻蚀对氧化铜的还原情况。结果发现在极其微弱的氩离子束流轰击下,CuO即被还原,刻蚀初期变化较大,之后达到稳恒状态。对Cu2p峰拟合,同时结合俄歇CuLMM峰变化,判定纯CuO经氩离子刻蚀后最终转变为氧化铜、氧化亚铜及少量单质铜的共存状态。研究结果将对氧化铜深度剖析中化学状态的判断具有重要参考价值。     

NdCl3-FeCl3-石墨层间化合物的XPS研究

通过熔盐交换法合成了ＮｄＣｌ３－ＦｅＣｌ３－ＧＩＣ,采用Ｘ射线电子能谱（ＸＰＳ）分析插入剂在石墨层间的存在形式,并测定了试样中Ｎｄ,Ｆｅ,Ｃｌ和Ｃ的相对含量。ＮｄＣｌ３－ＦｅＣｌ３－ＧＩＣ中Ｆｅ２ｐ的结合能为７１１．２０－７１０．３ｅＶ,Ｎｄ３ｄ的结合能为９８３．２０－９８３．０８ｅＶ,并发现Ｆｅ在石墨层ｅ＾３＋,Ｆｅ＾２＋形式存在。     

Photochemistry in the Low-Temperature Processing of Metal Oxide Thin Films by Solution Methods

Photochemistry has emerged in the last few years as a powerful tool for the low-temperature processing of metal oxide thin films prepared by solution methods. Today, its implementation into the fabrication procedure makes possible the integration of amorphous semiconductors or functional crystalline oxides into flexible electronic systems at temperatures below 350 °C. In this review, the effects of UV irradiation at the different stages of the chemical solution deposition of metal oxide thin films are presented. These stages include from the synthesis of the precursor solution to the formation of the amorphous metal-oxygen network in the film and its subsequent crystallization into the oxide phase. Photochemical reactions that can be induced in both the solution deposited layer and the irradiation atmosphere are first described, highlighting the role of the potential reactive chemical species formed in the system under irradiation, such as free radicals or oxidizing compounds. Then, the photochemical effects of continuous UV light on the film are shown, focusing on the decomposition of the metal precursors, the condensation and densification of the metal-oxygen network, and the nucleation and growth of the crystalline oxide. All these processes are demonstrated to advance the formation and crystallization of the metal oxide thin film to an earlier stage, which is ultimately translated into a lower temperature range of fabrication. The reduced energy consumption of the process upon decreasing the processing temperature, and the prospect of using light instead of heat in the synthesis of inorganic materials, make photochemistry as a promising technique for a sustainable future ever more needed in our life.     

Photoelectron Spectroscopy (XPS) and Cyclic Voltammetry (CV) Investigation of UxTh1-xO2 Thin Films

Thin film samples of UO₂ and U_0.55Th_0.45O₂ have been prepared by sputter co-deposition under argon atmosphere in presence of oxygen (reactive sputtering) onto gold foil. Films were characterized by X-Ray Photoelectron Spectroscopy (XPS). Cyclic Voltammetry (CV) studies have been made by using the thin films as electrodes in 0.01 M NaCl pH neutral non-purged electrolyte. The effect of thorium in the UO₂ lattice is observed by comparing the U_0.55Th_0.45O₂ electrode to the UO₂ electrode. The results indicate that uranium develops enhanced resistance to the oxidation when thorium is added to the lattice. After the CV measurements, the films were again characterized by XPS. The surface is enriched in thorium by 11%. Uranium is in a higher oxidation state; however, uranium is less oxidized in U_0.55Th_0.45O₂ than in UO₂.