XPS研究Nd表面氧化物的生长过程

用X射线光电子能谱(XPS)研究新鲜Nd表面在不同氧气和空气进气量的情况下,表面氧化物的生长过程.发现氧化层由氧化物、氢氧化物及表面化学吸附水三种成分,这三种成分的增加与进气量都存在正比对数关系,氧化物和吸附水在一定进气量后趋于饱和,而氢氧化物持续不断增加,最终氢氧化物占据主要地位. 关键词： X射线光电子能谱(XPS) Nd 氧化     

二氧化硅吸附铝离子的X射线光电子能谱(XPS)表征

用X射线光电子能谱技术研究了不同pH条件下二氧化硅对铝离子的吸附作用。在pH分别为3.74、4.25和4.88条件下,吸附在二氧化硅表面的铝离子的Al2p电子结合能依次为74.30、74.90、75.10eV。根据Al3 在水溶液中的一级水解常数pK1=4.99,认为在pH=3.74条件下,吸附在二氧化硅表面的铝离子的形态为Al3 ,而在其余两种pH条件下表面铝离子的形态为Al(OH)2 。     

CH4、CO2、O2制合成气用Ni-Ce/Al2O3催化剂的XPS研究

用XPS表征浸渍法制备的Ni-Ce／Al2O3催化剂,并与活性评价结果相关联,研究了添加Ce对催化剂性能的影响,探讨了催化剂失活的原因。结果表明,稀土Ce在反应过程中存在着部分还原变价过程(Ce^4 e→Ce^2 ),Ce^3 能够迁移至A12O3晶格,增强载体Al2O3的抗烧结能力,提高催化剂的稳定性;Ni-Ce/Al2O3催化剂表面的Ni和Ce在反应过程中向体相迁移,以及Ni晶粒的烧结是造成催化剂活性逐步下降的主要原因。     

硅片上超薄氧化硅层厚度测量的XPS标准曲线法

提出一种新的处理方法-XPS标准曲线法来测量硅片上超薄氧化硅层(SiO2/Si)的厚度。该方法利用一系列氧化硅厚度(d)准确已知的SiO2/Si标准样品,分别记录其氧化硅和元素硅的Si(2p)谱线,并得到峰高比(R),然后将厚度(d)对峰高比(R)作图得到标准曲线。在相同的实验条件下,测得未知样品氧化硅和元素硅的Si(2p)谱线并计算其峰高比,通过插入法在标准曲线上得到相应的氧化硅层厚度。SiO2/Si标准样品由设备一流和经验丰富的权威实验室提供,其氧化硅厚度采用多种方法进行测量比对。实验表明:基于氧化硅厚度准确知道的标准样品制作的XPS标准曲线,用于硅片上超薄氧化硅层厚度测量时具有快速、简便和比较准确等优点,有较好的实用价值。     

不同表面状态镀锡钢板铬酸盐钝化膜中铬元素的XPS分析

用X射线光电子能谱(X-ray photoelectron spectroscopy, XPS)分析的方法,对铬酸盐钝化镀锡钢板的正常表面及缺陷点处铬元素的含量、价态以及由铬元素组成的化合物进行了研究。用超声波的方法对铬酸盐钝化镀锡钢板进行处理后,研究了超声波处理对缺陷处的铬元素的含量、价态的影响。结果表明,钝化膜中主要含有Cr,O, Sn元素。镀锡铬酸盐钝化膜中正常表面的铬元素主要是以Cr(OH)₃,Cr单质以及Cr₂O₃的形态存在。在对镀锡板表面进行阴极电解钝化的过程中,Cr(Ⅵ)发生了转化,价态降低。在缺陷处,除了有Cr(OH)₃和Cr₂O₃以外,还有微量的Cr(Ⅵ)存在。在缺陷处铬元素的含量低于正常表面,在超声波清洗处理后,缺陷处铬元素的含量明显低于不经超声波清洗的含量。施加的超声波因产生强烈的洗脱作用,使吸附在缺陷处的微量的Cr(Ⅵ)消失。     

用XANES实验方法研究Cr的价态

用改进的XANES(X射线吸收近边结构谱)方法对不同比例Cr(Ⅲ)和Cr(Ⅵ)的酵母制剂进行Cr价态研究,该方法与传统方法的区别是用一个电离室同时进行透射和荧光XANES实验.此实验方法简单,快捷,特别适用于在相同的实验条件下,以一个已知标样为标准,对一系列未知价态样品进行的比较分析.实验结果表明酵母对Cr有很强的还原能力,它几乎能将所有的Cr(Ⅵ)还原成Cr(Ⅲ).Cr的K边XANES谱在掺入酵母剂前后有所变化,说明不同样品中的Cr原子近邻结构有所不同     

低速高电荷态重离子辐照的GaN晶体表面X射线光电子能谱研究

利用低速高电荷态Xeq+和Pbq+离子对在蓝宝石衬底上生长的GaN晶体膜样品进行辐照,并利用X射线光电子能谱(XPS)对样品表面化学组成和元素化合态进行了分析.结果表明,高电荷态离子对样品表面有显著的刻蚀作用;经高电荷态离子辐照的GaN样品表面氮元素贫乏而镓元素富集;随着入射离子剂量和所携带电荷数的增大,Ga—Ga键相对含量增大;辐照后,GaN样品中Ga—Ga键对应的Ga3d5/2电子的束缚能偏小,晶格损伤使内层轨道电子束缚能向低端方向偏移.     

基于XPS与XAS的稀磁半导体GaMnN电子结构研究

采用基于同步辐射技术的X射线光电子能谱(XPS)与X射线吸收谱(XAS)测试由金属有机化学气相沉积(MOCVD)技术制备的不同Mn掺杂浓度的稀磁半导体GaMnN薄膜的电子结构,探究Mn掺杂浓度对磁性原子Mn周围的局域环境和电子态等方面的影响,并阐述材料铁磁性变化的机理. XPS和XAS图谱分析表明：Mn²⁺和Mn³⁺共存于薄膜样品内,样品D中Mn²⁺占比高达70%-80%,N空位随Mn掺杂浓度增加而增多且N空位能够使空穴浓度降低,导致Mn 3d和N 2p轨道间的相互交换作用减小,从而减弱体系铁磁性.此外,Mn不同的掺杂浓度会影响GaMnN薄膜p-d耦合杂化能力的强弱,当掺Mn 1.8%时具有较强的p-d耦合杂化能力.     

沉积态铀薄膜表面氧化的X射线光电子能谱

含铀(U)薄膜在激光惯性约束聚变的实验研究中有重要的用途.研究其在不同气氛下的氧化性能可以为微靶制备、储存及物理实验提供关键的实验数据.通过超高真空磁控溅射技术制备了纯U薄膜及金-铀(Au-U)复合平面膜,将其在大气、高纯氩(Ar)气及超高真空度环境中暴露一段时间后,利用X射线光电子能谱仪结合Ar~+束深度剖析技术考察U层中氧(O)元素分布及价态,分析氧化产物及机理.结果显示,初始状态的U薄膜中未检测到O的存在.Au-U复合薄膜中的微观缺陷减弱了Au防护层的屏蔽效果,使其在3周左右时间内严重氧化,产物为U表面致密的氧化膜及缺陷周围的点状腐蚀物,主要成分均为二氧化铀(UO_2).在高纯Ar气中纯U薄膜仅暴露6 h后表面即被严重氧化,生成厚度不均匀的UO_2.在超高真空度环境下保存12 h后,纯U薄膜表面也发生明显氧化,生成厚度不足1 nm的UO_2.Ar~+束对铀氧化物的刻蚀会因择优溅射效应而使UO_2被还原成非化学计量的UO_(2-x),但这种效应受O含量的影响.     

GS-MBE生长的GaP/Si的XPS研究

利用X射线光电子能谱(XPS)深度剖析方法对气体源分子束外延(GS-MBE)生长的GaP/Si异质结构进行了详细的分析.其结果表明:(1)外延层内Ga、P光电子峰与GaP相相符,且组份分布均匀,为正化学比GaP.(2)在不同富PH₃流量条件下生长的样品,其表面富P量稍有不同,而GaP外延层内的测试结果相同.界面也未见有P的富集.(3)XPS剖析至GaP/Si界面附近,随外延层界面向衬底过渡,Si2p光电子峰向高结合能方向移动,且其结合能高于原衬底p型Si,接近于n型Si.但Ga、P光电子峰未发现有明显能移.(4)在XPS检测限内,外延层内和界面都未见有C、O等沾污.这一研究表明:无污染的本底超高真空、相对过剩的富₃生长环境、成功的Si衬底清洗方法等措施保证了GS-MBE生长出正化学比GaP/Si外延异质结构.     

氧化铝/二氧化铈X射线衍射及拉曼光谱研究

钢中氧化铝夹杂物尺寸大小严重影响钢材性能,细化或去除钢中夹杂物备受重视.由于钢中合金元素添加量相对于钢液过少,并在分析过程中存在误差,使用放大夹杂物反应的思路,研究了在高温1600℃时不同比例稀土二氧化铈粉末和氧化铝粉末的添加量对夹杂物的物相变化、尺寸大小的影响.对高温箱式炉设定程序进行升温、保温、随炉冷却,依据测试结...     

XPS analyses of lanthanides phosphates

XPS measurements were performed on lanthanide orthophosphates LnPO₄ (Ln: La, Ce, Nd, Gd), and correlated with XRD and some EDS analyses. Single lanthanide phosphates LnPO₄ and mixed lanthanide phosphates LnxLn^′1−xPO₄, all crystallized in a monoclinic structure similar to the monazite mineral. Results were examined qualitatively and quantitatively, by considering the Ln 3d lines, P 2p line and O 1s line.Ionic sputtering does not induce significant broadening nor an additional shift of the lanthanide peaks and does not have an effect on their chemical environments, except in the case of cerium. However, sputtering seems to significantly reduce the intensity of the O 1s and P 2p peaks, while Auger peaks of carbon and oxygen atoms interfere, respectively, with the 3d line of gadolinium and neodymium. Those phenomena are all the more important when the Nd and Gd content is weak and must be taken into account for a quantitative analysis of the spectra.The quantitative analyses reveal the expected results for single monazites. On mixed phosphates, the measured phosphorous and oxygen amounts are generally more valid for non-sputtered sample surfaces than for sputtered surfaces, while the calculated relative amount of lanthanides [Ln]/[Ln′] are correct in all the cases.One of the important goals of this work was to have a satisfactory value for the atomic ratio La/Gd, and particularly in the case of (La,Ce)PO₄ and (La,Gd)PO₄, to obtain good agreement between the calculated lanthanides ratio Nd/Gd and ratios estimated from XRD and EDS measurements.     

超分散剂在莠去津颗粒表面吸附的XPS和SEM分析

用X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)研究了聚羧酸型梳状共聚物超分散剂吸附于莠去津颗粒样品表面的电子状态,计算了吸附厚度。结果表明,吸附分散剂后,莠去津颗粒界面的N(1s)和Cl(2p)谱峰强度明显减弱,Cl(2s)几乎消失,C(1s),O(1s)和Na(1s)谱峰强度则明显增强,这主要是分散剂中C,O和Na的贡献,且吸附分散剂后能在莠去津颗粒界面形成良好的吸附保护膜,其厚度约为24 nm。用扫描电子显微镜(scanning electron microscope,SEM)研究了样品表面形貌,研究发现吸附分散剂后莠去津颗粒变小、分布有序,使莠去津在水中能够获得稳定的悬浮性能。本文研究结果为莠去津环保剂型悬浮剂的应用提供了重要信息。     

ITO靶材黑化物的X射线光电子能谱研究

利用X射线光电子能谱（XPS）分析了ITO靶材黑化物的化学组成，结果表明黑化物由In、Sn、O和C组成，相对原子百分含量In为34．35％，Sn为2．74％，O为52．65％，C为10．26％；In、Sn处于亚氧化状态；C有部分氧化。与原始靶材相比，黑化物的元素组成和化学状态发生了明显的变化。择优溅射最可能引起成分比例失常，真空残余的合C气体和泵油蒸汽被认为是污染C的直接来源。     

XPS characterization of naturally aged wood

Wood deterioration over time (by a simultaneously biological, chemical or physical attack) is an inevitable continuous process in the environment. This process destroys all heritage resulting in a loss of valuable old wooden structures and their properties. What type of deterioration occurs and how these processes impact the wood are important questions that need consideration if old wooden structures are to be studied and properly preserved.X-ray photoelectron spectroscopy (XPS) was employed to analyze the undegraded (sound wood of ∼6 years) and degraded lime wood (∼150 years, ∼180 years, ∼250 years) from painting supports, differing in terms of the provenance, conservation status and environmental conditions of storage. Elaborated XPS analysis (comparison of C and O individual spectra, decomposition for each atomic component, calculation of O/C ratio) provided a view of the composition of the sample surfaces analyzed. On the basis of these results, it was confirmed that significant changes occurred in the first period of ageing, the ∼150 years lime wood sample having the highest percent of the carbon atoms and the lowest percentage of oxygen atoms and, respectively O/C ratio. According to our previous studies (X-ray diffraction, FTIR spectroscopy, analytical pyrolysis combined with gas chromatography/mass spectrometry and ESR-spectroscopy results), these features could be attributed to the fact that hemicelluloses and amorphous cellulose are degraded in time, whereas the crystalline fraction of cellulose decreases more slowly than the amorphous one. Consequently, the observation may be made that lignin is not so easily degraded under the environmental conditions where paintings are frequently exposed.     

A study of the 42CrMo4 steel surface by quantitative XPS electron spectroscopy

Quantitative X-ray photoelectron spectroscopy was used to characterize the native oxide film formed on 42CrMo4 steel surface by air exposure in normal conditions. In order to determine the thickness and composition of the oxide layer we have used a stacking layer model together with experimental XPS sputtering depth profiling. At a nanoscale study, to obtain quantitative results one must take into account fundamental parameters like the attenuation depth of photoelectrons. We have found that both lepidocrocit (γ-FeOOH) and magnetite (Fe₃O₄) were present and the total thickness of the oxide layer was 16 monolayers.     

Adsorption and reaction of hydrogen sulfide on thin-film cerium oxide

The adsorption and reaction of hydrogen sulfide, H₂S, have been studied on cerium oxide thin films that were vapor deposited on Ru(0 0 0 1). The behavior of the H₂S was examined as a function of Ce oxidation state. H₂S weakly chemisorbs on fully oxidized CeO₂ desorbing near 155 K. Hydrogen from the H₂S reacts with the surface O to desorb as water between 200 K and 450 K. When ca. 20% of the Ce⁴⁺ is reduced to Ce³⁺ more H₂S dissociates to -OH and -SH and water is produced near 580 K. When the ceria is ca. 70% reduced, water formation is suppressed and H₂ desorbs near 580 K. S 2p photoelectron spectroscopy indicates the decomposition of H₂S into -SH and then -S as the sample is annealed from 100 K to 600 K. O 1s photoemission indicated the presence of H₂O and -OH.     

New interpretations of XPS spectra of nickel metal and oxides

A current interpretation of XPS spectra of Ni metal assumes that the main 6 eV satellite is due to a two hole c3d⁹4s² (c is a core hole) final state effect. We report REELS observation in AES at low voltages of losses (plasmons and inter-band transitions) corresponding to the satellite structures in Ni metal 2p spectra. The satellite near 6 eV is attributed to a predominant surface plasmon loss. A current interpretation of Ni 2p spectra of oxides and other compounds is based on charge transfer assignments of the main peak at 854.6 eV and the broad satellite centred at around 861 eV to the cd⁹L and the unscreened cd⁸ final-state configurations, respectively (L is a ligand hole). Multiplet splittings have been shown to be necessary for assignment of Fe 2p and Cr 2p spectral profiles and chemical states. The assignments of Ni 2p states are re-examined with intra-atomic multiplet envelopes applied to Ni(OH)₂, NiOOH and NiO spectra. It is shown that the free ion multiplet envelopes for Ni²⁺ and Ni³⁺ simulate the main line and satellite structures for Ni(OH)₂ and NiOOH. Fitting the NiO Ni 2p spectral profile is not as straightforward as the hydroxide and oxyhydroxide. It may involve contributions from inter-atomic, non-local electronic coupling and screening effects with multiplet structures significantly different from the free ions as found for MnO. A scheme for fitting these spectra using multiplet envelopes is proposed.     

High resolution XPS studies on hexadecafluoro-copper-phthalocyanine deposited onto Si(1 1 1)7×7 surface

High resolution X-ray photoelectron spectroscopy measurements have been performed onto ultrathin films of hexadecafluoro copper phthalocyanine deposited, at room temperature and in ultrahigh vacuum conditions, onto clean Si(1 1 1)7×7 substrate (silicon, Si). The measurements, performed at various film thicknesses, show a strong interaction between the molecule and the Si substrate. All the core level peaks present strong modifications induced by the substrate interaction. In particular the fluorine (F) spectrum clearly presents the effect of the interaction of some F atoms of the molecule with the substrate, which determines the formation of F–Si bonds while the copper spectrum indicates a charge transfer from the Si substrate. The changes observed in the other core level spectra have been attributed to a different charge distribution in the molecule, after the formation of F–Si bonds. We suggest a planar growth of these molecules on the Si substrate starting from the first layer.