Volume and surface polarization of electrets

An attempt is made, to obtain mathematical relations correlating the volume and surface effects of the dielectric to those of the electrical impedance of the dielectric system exhibited in the presence of a quasistatic sinusoidal electrical field. A new experiment is described to differentiate clearly the two types of polarizations in an electret.     

Quantitative analysis of binary alloys by XPS

A rapid method for a quantitative analysis of a multielement alloy is discussed. This method is independent of surface-roughness and contaminations. Co     

Generation of XPS Auger lines by bremsstrahlung

Bremsstahlung-induced Auger lines of kinetic energy 1500–2200 eV can be recorded in the normal operation of an X-ray photoelectron spectrometer. The relatively low intensities can be enhanced by substituting a beryllium foil window for the customary aluminum foil. Auger lines of aluminum, silicon, phosphorus, sulfur, and probably chlorine, are recorded most favorably, and should be useful in identification of chemical states.     

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Large piezoelectric d₃₃ coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically “soft” (microporous polytetrafluoroethylene PTFE) and “stiff” (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the two-layer fluoropolymer stack exceeds the d₃₃ coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing. Accepted: 9 November 1999 / Published online: 3 December 1999     

Characterization of oxidized CdS by SIMS/XPS

Although adsorption of simple gases is not detected on CdS by analytical means, oxidation is induced, for example, by exposure to a negative corona discharge [1] as well as by electron stimulation [2–4]. In the former case it was found that O attaches only to S, but in the latter case Cd is also oxidized. In this paper we investigate these processes by SIMS and XPS in an attempt to characterize and understand further these differences in behavior.     

The assessment of metal surface cleanliness by XPS

The most commonly used quantity to characterize surface cleanliness through X-ray photoemission spectroscopy (XPS) measurements is the so-called relative atomic surface concentration of carbon (at.% C). We have investigated the relationship between at.% C values and the C 1s peak area on Cu and we find a nearly linear behaviour in the range 15-80 at.% C. Correction factors for the measured at.% C values that enable a comparison of the cleanliness level of different materials, notably Cu, Al and stainless steel, have been determined experimentally.The influence of the storage time and method on the degree of re-contamination of initially clean Cu has been examined. The carbon contamination on clean metallic Cu increases abruptly to some 20 at.% C upon air exposure and continues to increase with storage time in air. Storage in polymer bags can lead to up to 70 at.% C after 1 month, whereas storage in aluminium foil can preserve an acceptable surface cleanliness for a similar storage time.     

MOCVD生长AlGaN薄膜的X光电子能谱

用X光电子能谱和X射线衍射谱方法分析了MOCVD生长的AlGaN薄膜的实际表面形态和晶体结构基于XPS测量结果,通过分析计算,发现实际表面除GaN外存在Ga₂O₃和Al₂O₃及其它与O有关的络合物构成的混合氧化物覆盖层,估计覆盖层厚度约1.2nmXRD结果显示生长的AlGaN薄膜为以GaN(0002)取向为主的多晶结构。     

Chemisorption of NO on Re studied by XPS

The adsorption of nitric oxide on clean rhenium has been studied by X-ray photoelectron spectroscopy. At room temperature only dissociative adsorption occurs; at 100 K, NO adsorbs molecularly at low coverages. Higher NO exposures lead to the formation of NO₂ which dissociates upon warming above 180 K.     

透明莫来石陶瓷薄膜的光电子能谱研究

采用溶胶－凝胶工艺合成了莫来石透明陶瓷薄膜。用Ｘ射线光电子能谱分析技术，通过Ｏ１ｓＡｌ２ｐ太Ｓｉ２ｐ的Ｘ射线光电子能谱分析，探讨了透明膜的结构，组成及阳离子的配位形态。研究表明，干凝胶中铝以ＡｌＯ６八面体为主，硅为ＳｉＯ４四面体，随温度的升高ＡｌＯ６向ＡｌＯ４转化，引进透明膜结构的相应变化。     

Determination of adsorbate coverages by leed and XPS

Layers of carbon, oxygen, sulfur and potassium adsorbed on an Fe(100) surface were studied by LEED, AES and XPS. When examined quantitatively by XPS, saturated c(2 × 2)CO(β), c(2 × 2)C and p(1 × 1)O surface structures yielded the C/O ratios expected from surface coverages of 0.25, 0.5 and 1.0 monolayer, respectively. When these results were normalized to the equivalent coverages of 1.0 monolayer, the relative XPS cross-sections obtained for S, O, C and K were found to agree closely with the results of theoretical calculations. The results illustrate the use of these techniques for the quantitative determination of surface coverages.     

Scope for simulating ionic conducting lattices as spherical electrets

Spherical electrets are proposed to simulate an ionic crystal lattice containing polarizable ions, whose electric fields persist for long periods. When there are conducting paths between the charged elements, polarization can exist in thin layers.Moscow State Institute for Electronics and Mathematics, Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 27–30, April, 1994.     

Magnetic fluids stabilized by polypropylene glycol

A series of samples of magnetic fluids stabilized with low-molecular weight polypropylene glycol (PPG) of different molecular masses were synthesized. The use of PPG allowed the maximum extension of the carrier fluid range to include ethyl- and butyl-acetate, ethanol, butanol, acetone, carbon tetrachloride, toluene, kerosene and PPG itself. Magnetic and rheological properties of the samples were investigated. Based on the results of investigation it has been concluded that magnetic nanoparticles are covered by a monolayer of surfactant molecules. At low temperatures the propanol-based sample preserves fluidity up to −115 °C. Measurement of critical temperatures of other base fluids showed that alcohols are the best carrier medium. Coagulation stability of the ethanol-based ferrocolloid with respect to water and kerosene was explored. It has been found that kerosene, whose fraction by weight exceeds 22.5%, does not mix with the colloid. This effect can be used to produce magneto-controllable extractors of ethyl alcohol. Under the action of water the colloid coagulates, which allows one to substitute the carrier fluid and to separate the colloid into fractions.     

Tobacco alkaloids analyzed by Raman spectroscopy and DFT calculations

The tobacco alkaloids: nicotine, nornicotine, cotinine, anabasine, their protonated forms, and salts were analyzed by means of Raman spectroscopy supported by the density functional theory/B3LYP/aug‐cc‐pVDZ calculations. The analyses were performed based on Raman marker bands of neutral, monoprotonated, and diprotonated forms of tobacco alkaloids because in different surroundings various forms have been suggested to either dominate or to coexist. The form and distribution of nicotine directly in a plant and in phytopharmaceutical products were investigated by in situ Raman mapping. For the first time, the Raman optical activity spectrum of (−)‐nicotine in aqueous solution was measured and interpreted by means of the density functional theory calculations. The study provides a clear evidence that Raman spectroscopy techniques are powerful in efficient quality control and forensic and bioanalytical analyses of tobacco alkaloids. Copyright © 2012 John Wiley & Sons, Ltd.     

Material microstructures analyzed by using gray level Co-occurrence matrices

The mechanical properties of materials greatly depend on the microstructure morphology. The quantitative characterization of material microstructures is essential for the performance prediction and hence the material design. At present,the quantitative characterization methods mainly rely on the microstructure characterization of shape, size, distribution,and volume fraction, which related to the mechanical properties. These traditional methods have been applied for several decades and the subjectivity of human factors induces unavoidable errors. In this paper, we try to bypass the traditional operations and identify the relationship between the microstructures and the material properties by the texture of image itself directly. The statistical approach is based on gray level Co-occurrence matrix(GLCM), allowing an objective and repeatable study on material microstructures. We first present how to identify GLCM with the optimal parameters, and then apply the method on three systems with different microstructures. The results show that GLCM can reveal the interface information and microstructures complexity with less human impact. Naturally, there is a good correlation between GLCM and the mechanical properties.     

Hysteretic giant magnetoimpedance effect analyzed by first-order reversal curves

We applied the first-order reversal curve method to hysteretic giant magnetoimpedance (GMI) of soft magnetic amorphous ribbons with a well-defined transversal domain structure and quasi-anhysteretic magnetization behavior. In opposition to major curve, it gives access to the distribution of local irreversible changes of the transverse permeability, which undergo a gradual transition. Results show that hysteretic GMI effect consists of three distinct regimes depending on the applied field. An interlinked hysteron/anti-hysteron model is proposed to analyze the obtained results, which allows one to follow the influence of frequency and anisotropy upon the irreversible switches probed by GMI.     

Nanoscopic photodeposited structures analyzed by an evanescent optical method

The evanescent field propagating in waveguides was used to evaluate the profile and growth rate of laser photodeposited a-Se. A pulsed KrF excimer laser was used for deposition. The differential-evanescent light leaking image, was used to analyze the nanostructures in the deposited zones. The relation between the emerging light intensity of the evanescent wave and the optical light intensity propagating in the waveguide was connected to an effective range of the evanescent wave leaking power into the deposited material. The technique provides the nanometric profiles of the ultra-thin photodeposited structures.     

PLA-PMMA blends: A study by XPS and ToF-SIMS

This paper reports which are the possibilities of quantification by time of flight secondary ion mass spectrometry (ToF-SIMS) for some polymer blends. In order to assess the composition of the mixtures, we studied first different poly(l-lactide)/polymethylmethacrylate (PLA/PMMA) blends by X-ray photoelectron spectroscopy (XPS), this technique being quantitative. By XPS fitting of the C 1s level, we found a very good agreement of the measured concentrations with the initial compositions. Concerning ToF-SIMS data treatment, we used principal component analysis (PCA) on negative spectra allowing to discriminate one polymer from the other one. By partial least square regression (PLS), we found also a good agreement between the ToF-SIMS predicted and initial compositions. This shows that ToF-SIMS, in a similar way to XPS, can lead to quantitative results. In addition, the observed agreement between XPS (60-100 Å depth analyzed) and ToF-SIMS (10 Å depth analyzed) measurements show that there is no segregation of one of the two polymers onto the surface.