X射线光电子能谱(XPS)

在对许多材料的研究和应用中,了解其表面特性是很重要的。而要获得材料的表面特性,就需要一些特殊的仪器,对各种材料从成分和结构上进行表面表征。其中,X射线光电子能谱(XPS)由于其对材料表面化学特性的高度识别能力,成为材料表面分析的一种重要技术手段。 X射线光电子能谱的基本原理(图1)是当一束特定能量的X射线辐照样品,在样品表面发生光电效应,就会产生与被测元素内层电子能级有关的具有特征能量的光电子,对这些光电子的能量分布进行分析,便得到光电子能谱图。XPS起始于发现光电效应之后不久,1914年Rutherford即成功地表述了XPS的基本方程:     

射频磁控溅射钛镀层与陶瓷界面的X射线光电子能谱研究

本文采用XPS配合Ar+离子原位刻蚀研究了用射频磁控溅射法制备Ti/Al₂O₃(0001),Ti/Al₂O₃(多晶)和Ti/MgO(001)体系的界面结构。结果表明,在Ti/Al₂O₃体系的界面处存在Al3+的还原态和Ti的氧化态,且在刻蚀过程中,Al3+的还原态出现在Ti的氧化态之前。用相同方法制备的Ti/MgO界面没有产生类似的界面反应。     

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.     

磁性多层膜的X射线光电子能谱研究

用射频 /直流磁控溅射法制备了NiOx/Ni81Fe19和Co/AlOx/Co磁性薄膜。利用X射线光电子能谱研究了NiOx 对Ni81Fe19耦合交换场Hex与NiOx 化学状态的关系以及Co/AlOx/Co磁性薄膜中AlOx 对Co膜的覆盖状况。结果表明 :Hex的大小只与 2价镍有关 ,单质镍和 3价镍对Hex没什么作用 ;在Co/AlOx/Co磁性薄膜中 ,Al层将Co膜完全覆盖所需要的最小厚度为 2 .0nm ,用角分辨XPS测出的Al氧化厚度为 1 15nm     

X射线光电子能谱技术在材料表面分析中的应用

X射线光电子能谱技术是一种表面分析技术,不仅能够定性和定量分析材料表面的元素组成和含量,而且可以分析元素的化学价态、化学键等信息.本文通过阐述XPS的基本原理、应用、特点、常见问题及解决办法等,讨论了X射线光电子能谱技术在材料表面分析中的具体应用,并展望了其在计量领域的发展前景.     

电沉积Ni-W合金镀层的X射线光电子能谱分析

采用X射线光电子能谱（XPS）对电沉积Ni-W合金镀层表面膜进行了分析。研究结果表明，Ni-W合金镀层表面存在一层薄的氧化膜，而钨的氧化作用远大于镍，Ni-W合金镀层中W含量的提高对耐蚀性起决定作用。     

Ar离子轰击高定向石墨表面结构变化的X射线光电子能谱分析

用X射线光电子能谱（XPS）研究了3．0keV Ar离子轰击高定向裂解石墨（HOPG）引起的表面结构的变化。通过对C1sC KLL及C2s谱峰形状的定性和定量分析，表明Ar离子轰击将破坏共价π键并导致表面局域sp^2杂化C键向sp^3杂化C键转化。sp^3／sp^2之比依赖于离子轰击时间。     

磁性多层膜的Ф射线光电子能谱研究

用射频／直流磁控溅射法制备了ＮｉＯｘ／Ｎｉ８１Ｆｅ１９和Ｃｏ／ＡｌＯｘ／Ｃｏ磁性薄膜。利用Ｘ射线光电子能谱研究了ＮｉＯｘ对Ｎｉ８１Ｆｅ１９耦合交换场Ｈｅｘ与ＮｉＯｘ化学状态的关系以及Ｃｏ／ＡｌＯｘ／Ｃｏ磁性薄膜中ＡｌＯｘ对Ｃｏ膜的覆盖状况。结果表明：Ｈｅｘ的大小只与＋２价镍有关,单质镍和＋３价镍对Ｈｅｘ没有什么作用;在Ｃｏ／ＡｌＯｘ／Ｃｏ磁性薄膜中,Ａｌ层将Ｃｏ膜完全覆盖所需的要最小厚度为２．０ｎ     

NiAl2O4材料的X射线光电子能谱分析

多晶半导体陶瓷材料ＮｉＡｌ２Ｏ４是一种很有应用价值的高温热敏材料。本文介绍了这种材料的合成方法，并用ＸＲＤ技术分析该材料在不同合成温度下的相态及晶体结构。结果表明：合成物主晶相为尖晶石型Ｎｉ１－ｘＡｌ２Ｏ４，次晶相为ＮｉＯ，且随合成温度的提高，ＮｉＯ含量大幅度减少。本文根据ＸＰＳ分析结果，重点讨论了样品中各元素在不同合成温度下的结合能位移。分析表明：Ｎｉ１－ｘＡｌ２Ｏ４中存在有Ｎｉ空位，随着合成温     

用X射线光电子谱研究Pt和CeO2间的相互作用

用X射线光电子谱研究了CeO2和Pt间的相互作用,探讨了通过相互作用能提高CeO2的氧化还原反应活性的机理,并与通常的金属和载体强相互作用的机理进行了比较.对高结合能端O1s峰和表面O-离子的产生过程进行了讨论.     

Quantitative X-ray Rietveld analysis of metallic aluminum content in nano-aluminum powders

Accurate analysis of the content of metal aluminum (Al) in nano-Al powders is a difficult task due to the high reactivity of nano-Al powders. Here, the X-ray Rietveld quantitative phase analysis (QPA) method was applied to analyze the content of metal aluminum in nano-Al powders produced by three methods. A good agreement between the observed and calculated diffraction pattern was obtained and the conventional Rietveld factors (R_p, R_wp and GOF) converged to satisfactory values, which suggested that Al content was evaluated accurately. At the same time, the mixture sample of 89.77 wt.% micro-Al + 10.23 wt.% α-Al₂O₃ was study and the fitting pattern and R factors were satisfactory, which further verified the reliability of the X-ray Rietveld QPA method.     

X-ray diffraction and X-ray photoelectron spectra of Fe-Cr-N films deposited by DC reactive sputtering

The effects of nitrogen flow ratio, target area ratio of Cr, and substrate temperature on the structure of DC reactive sputtered Fe-Cr-N ternary films have been studied. X-ray diffraction measurements show that Fe-Cr-N films consist of -Fe(Cr) and -(Fe,Cr)₄N_x (x<1) phases. The crystal grain of the -Fe(Cr) phase becomes finer and a (200) texture of the -(Fe,Cr)₄N_x phase becomes more marked with increasing the nitrogen flow ratio. X-ray photoelectron spectra of the films show that oxidation resistance of Fe-Cr-N films is superior to that of Fe-N films, and oxides are formed only in the film surface due to contacting with the ambient atmosphere and oxygen contamination is very small in the inner parts of these films.     

Application of auxiliary metal layers to e-beam and X-ray lithography

Micron and sub-micron gold lines have been produced by liftoff following e-beam and X-ray exposures of resist coated chromium layers on silicon. Etching a 0.1 micron chromium layer after development results in an undercut which aids the liftoff process. This approach has been used in e-beam lithography on PMMA (i.e. positive resist) to decouple the e-beam exposure from generation of the undercut. In this way 0.7 micron gold lines separated by less than 0.3 microns have been produced. A similar approach when used in X-ray lithography on OEBR (negative resist) yielded gold lines down to 0.3 microns in width and separation. Scanning electron micrographs of patterns at various stages of processing are presented and the profiles of the resist walls and the nature of the undercut are described.     

Phase formation in yttrium aluminum garnet powders synthesized by chemical methods

Yttrium aluminum garnet (YAG) powders were synthesized by precipitation of hydroxides using three types of precursors: nitrates (nitrate process), isopropoxides (alkoxide process), and isopropoxides chelated with ethyl acetoacetate (modified alkoxide process). The phase development in the powders during heat treatments was investigated with DTA and XRD. An intermediate hexagonal YAlO₃ (YAH) phase was formed at 800°C in all powders regardless of the synthesis processes, but its complete transformation to YAG at higher temperatures (1000°C) occurred only in the powders prepared by the nitrate and modified alkoxide processes. The alkoxide process led to the largest deviation from the bulk composition, producing a single phase of YAH that transformed into YAG plus a stable YAM (Y₄Al₂O₉) phase. The modified alkoxide process led to the most homogeneous bulk composition, resulting in the least amount of YAH in the powder. The poor chemical homogeneity in the powders prepared by the nitrate and alkoxide processes was attributed to the segregation of the hydroxides and to the presence of the double alkoxide, respectively.     

Differentiation of domains in composite surface structures by charge-contrast X-ray photoelectron spectroscopy

An external bias is applied to two samples containing composite surface structures, while recording an XPS spectrum. Altering the polarity of the bias affects the extent of differential charging in domains that are chemically or electronically different to create a charge contrast. By utilizing this charge contrast, we show that two distinct silicon nitride and silicon oxynitride domains are present in one of the composite samples. Similarly, we use this technique to show that titanium oxide and silicon oxide domains exist as separate chemical entities in another composite sample.     

Characterization of lead oxides by X-ray photoelectron spectroscopy and thermal analysis methods

X-ray photoelectron spectroscopy (XPS) and thermal analysis were used to study a series of lead oxides. X-ray photoelectron spectra suggest that some minium (Pb3O₄) samples contain carbonate groups and an excess of oxygen in superficial layers. These samples, if used in paints' production cause their premature thickening. The combined results provide compositional evidence for the mechanisms occurring at surfaces of underoxidized minium and leading to the formation of hydroxyl and subsequently carbonate species.