原子力显微镜与X射线光电子能谱对ITO表面改性的研究

采用氧气等离子体(OP)处理对氧化铟锡(ITO)薄膜进行表面改性,通过原子力显微镜(AFM)、X射线光电子能谱(XPS)和四探针等测试手段对薄膜样品进行表征,研究了OP处理对ITO表面性质的影响.实验结果表明OP处理有效去除了ITO表面的污染物,优化了ITO表面的化学组分,降低了ITO表面的粗糙度和方块电阻,改善了ITO的表面形态.与此同时,通过XPS监测研究了OP处理后ITO表面化学组分随老化时间的变化,结果显示经过优化的化学组分随老化时间增加而逐渐退化.另外,以OP处理后经过不同老化时间的ITO样品作为空穴注入电极,制备了有机电致发光器件(OELD),通过测试器件的电压-电流-亮度特性,进一步研究了ITO表面性质对于OELD光电性能的影响.     

X-ray photoelectron spectroscopy and conducting atomic force microscopy investigations on dual ion beam sputtered MgO ultrathin films

Ultrathin films of MgO (~ 6 nm) were deposited on Si(100) using dual ion beam sputtering in different partial pressures of oxygen. These thin films were characterized by X-ray photoelectron spectroscopy (XPS) for chemical state analysis and conducting atomic force microscopy for topography and local conductivity map. No trace of metal Mg was evidenced in these MgO films. The XPS analysis clearly brought out the formation of oxygen interstitials and Mg(OH)₂ primarily due to the presence of residual water vapors in the chamber. An optimum value of oxygen partial pressure of ~ 4.4 × 10^− 2 Pa is identified with regard to homogeneity of film and stoichiometry across the film thickness (O:Mg::0.93-0.97). The local conductivity mapping investigations also established the film homogeneity in respect of electrical resistivity. Non-linear local current-voltage curves revealed typical tunneling characteristics with barrier width of ~ 5.6 nm and barrier height of ~ 0.92 eV.     

Surface modification of polystyrene and poly(ethylene terephtalate) by grafting poly(N-isopropylacrylamide)

In this work, poly(N-isopropylacrylamide) (PNIPAAm) was incorporated into previously oxidized PS and PET surfaces by grafting using two photo-initiation pathways. The incorporation of PNIPAAm was observed by drop water contact angle measurements, dyeing with Methylene Blue and AFM images analysis of the virgin and modified polymers. It was verified that the grafting process depends on the chemical surface environment. The grafted surfaces are hydrophilic below 32 °C and hydrophobic above this temperature. The transition is due to the incorporated PNIPAAm. This characteristic gives to the grafted materials potential to be applied as biomaterials.     

Atomic force microscopy and X-ray photoelectron spectroscopy study on nanostructured silver thin films irradiated by atomic oxygen

Nanostructured silver thin films irradiated by atomic oxygen (AO) generated in a ground simulation apparatus were investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM results show that after irradiation, all the grain sizes of the thin films became more or less small, and the compact surface became rough and sparse. From XPS depth profile of an AO-irradiated silver thin film, it can be found that the silver oxides formed exist as two valences, that is, at the surface, the oxide is mainly AgO, and gradually change to Ag₂O, the content of unoxidized silver also increase with depth of film.     

Characterization of polyacrylonitrile films grafted onto nickel by ellipsometry, atomic force microscopy and X-ray reflectivity

The thickness and roughness of polyacrylonitrile films electrografted on a nickel surface have been measured by ellipsometry, atomic force microscopy and X-ray reflectivity. From combined ellipsometry and X-ray reflectivity measurements, accurate values for the refractive indices of polyacrylonitrile and nickel have been derived at a 6328-Å wavelength. Dependence of the film thickness on the monomer concentration has been quantified for the first time. Furthermore, the thickness of the polyacrylonitrile (PAN) film is related to the nature of the solvent, depending on whether it is a good solvent for PAN (dimethylformamide; DMF) or not (acetonitrile; ACN).     

X-ray photoelectron spectroscopy characterization of poly(2,3-diaminophenazine) films electrosynthesised on platinum

Films of poly(2,3-diaminophenazine) (PDAPh) were obtained on platinum substrates by electropolymerization (cyclic voltammetry, CV) of the monomer in acidic solutions. Limited investigations were performed by cyclic voltammetry and quartz crystal microbalance (QCM). CV showed that phenazine units are present along the polymer chains and exhibit their peculiar electrochemistry. QCM measurements confirmed the deposition of a film on the electrode surface during cyclic voltammetry on 2,3-diaminophenazine (DAPh) solutions. Film structures were thoroughly investigated by X-ray photoelectron spectroscopy (XPS) analysis both through curve fitting of C1s and N1s signals. XPS was also performed following chemical derivatization of samples for NH₂, CO, COOH and OH groups with fluorinated markers. As a result, the presence of NH₂ groups could be excluded, COOH and CO groups were found to be minor defects, whereas OH groups, more abundant, were assigned partly to oximic groups (-CN-OH). The possible presence of other structural defects involving nitrogen (N-N and N⁺-O⁻groups) was also suggested by XPS. Finally, theoretical calculations on electron spin densities of 2,3-diaminophenazine radicals seem to support a 1,2 coupling mechanism for 2,3-diaminophenazine electrochemical polymerization.     

Atomic force microscopy and X-ray photoelectron spectroscopy study of chitosan-carbon fiber materials

Chitosan-carbon materials produced by electrochemical deposition of chitosan on an activated carbon fiber (ACF) as an electrode have been studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM data demonstrate that the microstructure of the coating depends on whether chitosan is deposited in soluble or insoluble form. XPS data are used to evaluate the state of chitosan in the composites in relation to the deposition conditions.     

Surface analysis of different wood species using X-ray photoelectron spectroscopy (XPS)

X-ray photoelectron spectroscopy (XPS) was used to characterize the surfaces of mechanically treated wood. Microtomed and sanded surfaces of spruce, larch, beech and oak were investigated. Changes due to the sanding process were identified from the survey spectra as well as from the detailed C1s spectra. The changes were quantified with the atomic ratio of oxygen to carbon and with a detailed analysis of the contributions to the C1s peak. The identified changes were explained in terms of the macromolecular wood substances and in terms of density and the amount of extractives.     

Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy

Submicrometer-sized particles of poly(N-isopropylacrylamide) (PNIPAM) are synthesized by surfactant-free radical polymerization. The morphology and nanomechanical properties of individual, isolated PNIPAM microgel particles at the silicon/air and silicon/water interfaces, below and above the PNIPAM volume-phase-transition temperature (VPTT), are probed by atomic force microscopy. In air, and in water below the VPTT, the PNIPAM spheres are flattened and adopt a pancakelike shape. Interestingly, above the VPTT the microgels adopt a more spherical form with increased height and decreased width, which is attributed to reduced interactions of the particles with the substrate. The elastic modulus calculated from force-indentation curves obtained for individual microgel spheres reveals that the stiffness of the particle's surface decreases by two orders of magnitude upon swelling in water. Additionally, the modulus of the PNIPAM spheres in water increases by one order of magnitude when crossing the VPTT from the swollen to the collapsed states, indicating a more compact chain packing at the particle surface.     

Surface oxide dissolution in titanium subhydrides studied by Auger electron spectroscopy and X-ray photoelectron spectroscopy

The surface sensitive spectroscopic techniques of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) have been applied to the study of oxide dissolution of titanium subhydrides. In an earlier study using AES, it was shown that the rate of oxygen dissolution into titanium increased sharply at ~350° C. These data correlated well with physical property measurements that indicated an exothermic reaction was occurring at these temperatures which corresponded to the reaction of free titanium with atmospheric oxygen. In the present study the work has been expanded to include studies of TiH _x (x=1.15, 1.62). It has been found that dissolution of the native oxide on titanium subhydrides occurs at a temperature substantially higher (~ 500° C) than that required for titanium. It appears that the outward diffusion of hydrogen is inhibiting the inward diffusion of oxygen on the subhydride samples at temperatures below 500° C.Mound Facility is operated by Monsanto Research Corporation for the United States Department of Energy under Contract Number DE-AC04-76-DP00053.     

Mapping of thermoplastic elastomeric nitrile rubber/poly(styrene-co-acrylonitrile) blends using tapping mode atomic force microscopy and transmission electron microscopy

Dynamically vulcanized thermoplastic elastomeric blends of nitrile rubber (NBR)/poly(styrene-co-acrylonitrile) (SAN) were mapped by tapping mode atomic force microscopy (TMAFM) and transmission electron microscopy (TEM). The morphology changes with the blend ratio and dynamic vulcanization. Roughness and surface analysis were used to study the effect of dynamic vulcanization and mixing sequence on the surface texture of the thermoplastic elastomeric blends. Surface geometry was quantified by power spectral density (PSD) and fractal analysis.     

Microstructural examination of layered coatings by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy

The structure of r.f. sputtered multilayer Ti-BN coatings was investigated by low-voltage scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, and atomic force microscopy. Appropriate specimen preparation methods are described for each technique; these included fracture of the substrate, masking the growing film to produce a taper section, and ion-beam milling of embedded cross sections. Correlation of scanning electron micrographs with atomic force images was facilitated by the presence of similar composition contrast in both cases. Quantitative X-ray microanalysis of the layers was performed using the φ(z) approach. The crystal structures of nanocrystalline grains nucleated as a result of interdiffusion reactions during thermal annealing were identified by selected-area electron diffraction and convergent-beam microdiffraction as -titanium and f.c.c. titanium nitride.     

Surface characterization of natural graphite powder composite electrodes by atomic force microscopy

Graphite powder electrodes bonded by polymerized LaPO₄ have been investigated for the first time by atomic force microscopy (AFM). The interest in investigating this material stems from the fact that graphite electrodes intercalated, or not, with various metals and bonded with LaPO₄ have shown very good mechanical and electrochemical stability during the hydrogen evolution reaction (HER) in 1 M KOH aqueous solutions. Examination of their surfaces by scanning electron microscopy has revealed that these electrodes are very porous. AFM furnishes additional data about the surface and can therefore be considered a powerful tool for surface characterization.     

Surface roughness characterization of Nicalon and HI-Nicalon ceramic fibers by atomic force microscopy

The behavior of ceramic composites is governed by the nature of the fiber/matrix interface. Fiber surface roughness is a key parameter in the behavior at the fiber/matrix interface (e.g., debonding, interfacial sliding) and the overall behavior of a composite. Using an atomic force microscope (AFM), quantitative surface roughness values of ceramic fibers can be obtained, with an uncertainty of 1nm. The AFM technique was used to obtain surface roughness profiles and analysis on Si-C-O and Si-C fibers (Nicalon, and a new, virtually oxygen-free Si-C fiber, HI-Nicalon). The latter fiber had a slightly higher roughness amplitude, which may be caused by differences in processing. Although the differences in roughness between the fibers were small, the calculated radial strain and radial normal stress in composites reinforced with HI-Nicalon were higher than in those reinforced with Nicalon. This result indicates that small changes in the roughness of a fiber can significantly affect the debonding and sliding properties between the fiber and matrix.     

并五苯薄膜的AFM及XRD研究

报道了以热氧化硅片为衬底,用溶液溶解和真空蒸镀两种方法制备有机半导体材料并五苯薄膜.用原子力显微镜(AFM)分析了薄膜的形貌,用X射线衍射仪(XRD)分析了薄膜的晶体结构,讨论了诸多因素对薄膜的影响以及两种方法制备的并五苯薄膜的相结构.     

Mechanical,atomic force microscopy and focussed ion beam studies of isotactic polystyrene/titanium dioxide composites

Composites of isotactic polystyrene with different loading of titanium dioxide were prepared by melt mixing in a Brabender Plasticorder at a rotor speed of 60 rpm at 180 °C. Mechanical properties of the composites were measured by various techniques and most of the properties were found to be increasing with filler loading. Tapping mode atomic force microscopy was used to study the surface characteristics of the composites. Various AFM analytical parameters like power spectral density, roughness analysis and section analysis were measured. The mechanical properties of the composites were correlated with analytical data obtained from the AFM studies. The focused ion beam technique was also used to characterize the dispersion of the filler in the polymer matrix.