X射线光电子能谱复杂谱图的非线性最小二乘法分析案例

X射线光电子能谱(XPS)是材料表面分析表征最常用的测试手段之一,然而由于XPS数据处理过程中往往会带入主观因素,其数据分析往往是一个难题.本文重点报道了 XPS复杂数据分析的处理方法和案例,首先总结了非线性最小二乘法(NLLSF)分析XPS复杂谱图的适用范围;随后根据谱峰重叠的类型对实际测试分析过程中遇到的复杂数据进...     

LaMn1-xCuxO3的清洁表面和吸附表面的XPS研究

用XPS研究了LaMn_(1-x)Cu_xO_3的表面性质。实验表明对0≤x≤0.6,芯态谱能够清楚地区分最表面层和次表面几层的电子结构。组成元素中的氧和镧的含量不随x值而变化,二者维持很好的化学组成比。铜和锰在最表面单层的x值与次表面的有很大差别。清洁表面存在锰的富集。对(CO)吸附表面,情况相反。吸附的碳存在两个谱峰,这与吸附表面的复杂的铜谱相对应。对镧谱的分析得到两个伴峰,而不是通常认为的一个伴峰。价带谱的O(2p)峰位和价带顶与催化活性有一定的对应关系。     

峰宽法快速测定程序升温脱附活化能

TPD技术^[1]已成为研究固体表面性质的重要手段,本文在总结前人工作的基础上考察了TPD谱峰峰宽和相应参数与脱附活化能(E_d)之间的变化规律,证明用任意峰宽法或半峰宽法测定E_d值有很好的实用性,该法直接运用TPD谱图参数,无需另外作图,故十分快速、简便,与其它方法比较,结果吻合。     

西尼地平核磁共振碳谱氢谱的谱峰归属

利用普通1H-NMR，13C-NMR，极化转移谱(DEPT)以及同核相关谱(COSY)、异核相关谱(HSQC)，特别是远程偶合谱(HMBC)等多种核磁研究方法对新型的血管扩张药西尼地平的1H、13C信号进行完全归属。对由于分子结构对称而引起的化学位移相差最小为0．94Hz的两个碳加以区分，解决了由于样品的近似对称性而导致几组谱峰难以归属的问题。     

六氟磷酸二(4,4'-二甲基-2,2'-联吡啶)·(2,2'-联吡啶-4,4'-二羧酸)合钌(Ⅱ)的二维核磁共振

用1H NMR和13C NMR谱研究了新型电化学发光探针六氟磷酸二(4,4'-二甲基-2,2'-联吡啶)·(4,4'-二羧酸-2,2'-联吡啶)合钌(Ⅱ)的立体结构,通过1H-1H COSY、13C-1H HETCOR谱对其氢谱和碳谱中的各谱峰进行了归属,并给出了氢谱和碳谱峰的化学位移值.     

基于无基底扣除的数据趋势累积谱峰检测算法

谱峰的检测分析在色谱技术研究中具有十分重要的作用,但在色谱数据采集、传输的过程中,不同程度的噪声干扰给谱峰检测带来了极大的困难。目前传统的谱峰检测算法普遍通过基底扣除的方式对谱峰的形态进行预定义,将谱峰分为单峰、重叠峰等多个种类。针对不同种类的谱峰采用不同的检测方法,这就导致了传统的谱峰检测算法具有高复杂度、低自动化程度以及容易失真等缺点。因此,该文从另一个角度出发提出了一种新型的谱峰检测算法。该算法取消基底扣除以及谱峰分类这一步骤,直接在源数据曲线的基础上进行谱峰检测,主要分为离散差分、趋势累积以及遍历寻峰3个步骤。首先通过信号量表征数据升降趋势;然后进行数据趋势累积,根据累积总和定位谱峰,采用三点定位的方式,即峰起点、极值点和峰终点描述一个谱峰的位置;最后根据遍历排序的方式进行谱峰的筛选。此外,通过谱峰扣除的方式得到曲线基底部分。采用C语言设计编写了算法程序,并对多个动态比表面积分析仪测定的色谱图进行了检测分析,结果显示使用该算法可以精准区分谱峰部分与基底部分,受数据曲线毛刺、震荡等噪声干扰很小,谱峰的三点定位十分准确,且不受其复杂形态的影响,具有很强的普适性。与其他算法相比,该算法定位准确,结构清晰,具有较好的稳定性以及可靠性。该文报道了无基底扣除以及趋势累积等新型谱峰检测思想在吸脱附色谱曲线中的应用,证明了其在吸脱附色谱峰检测中的有效性和良好的应用前景。     

烟煤快速加氢热解的研究——Ⅴ.煤和半焦中有机硫化学形态剖析

采用XPS技术分析了我国以烟煤为主的七种煤样以及对应的快速加氢热解半焦中有机硫的化学形态。煤中有机硫一般为脂肪类硫与噻吩类硫,其谱位置分别在163.1-163.5eV和164.1-164.5eV之间。噻吩类硫的相对含量随煤化程度而增大。半焦中一般只残留噻吩类硫,谱峰位置在164.1-164.5eV,与对应煤中噻吩硫的谱峰位置是一致的。在加氢热解过程中全部脂肪类硫和部分噻吩类硫被脱除,脂肪类硫表现出很高的加氢反应活性。     

陶瓷基钛掺杂硅胶块体吸附剂研究

以陶瓷纤维纸为基材, 顺次经水玻璃、酸性硫酸氧钛溶液浸渍共沉淀制得新型蜂窝状陶瓷基钛掺杂硅胶块体吸附剂. FTIR谱在波数954 cm^－1附近的特征吸收峰表明钛掺杂硅胶中存在Si-O-Ti键; XRD谱显示掺杂材料为无定型非晶相材料; SEM显示钛掺杂硅胶粒子较好地分散在陶瓷纤维表面及其空隙中; 用EDS及XPS揭示了材料的组成和钛原子含量, 根据钛掺杂前后XPS中Si2p, O1s, Ti2p 3/2电子结合能变化以及²⁹Si MAS NMR中硅原子化学位移差异, 进一步表明钛原子替代硅原子进入了四面体骨架; BET分析显示掺杂材料以中孔为主. 与硅胶相比, 由于钛掺杂, 其比表面积、孔容增大, 吸附性能、耐热性能增强.     

高T~cYBa~2Cu~3O~7-xF~y超导体表面和体相的化学态的XPS研究

以NH~4F作为F^-源,制备了一系列不同含F量的高T~cYBa~2Cu~3O~7-xF~y超导体,在名义F含量小于1.5mol范围内,基T~c值均比与之对照的不含F样品高2～6K.用XPS研究了这类含F材料表面和体相的化学态及其变化,根据同种化合物中不同元素间的结合能差和其它辅助实验结果,标识了每个元素不同化学态的光电子峰,并对各个峰的可能来源及其对应原子在结构中的位置和作用进行了讨论.结果揭示,表现和体相的体学态存在着较大差异.     

衬底温度对强流脉冲离子束烧蚀沉积类金刚石薄膜化学结构的影响

采用强流脉冲离子束(High-intensitypulsedionbeam,HIPIB)烧蚀技术在Si(100)基体上沉积类金刚石(Diamond-likecarbon,DLC)薄膜,衬底温度的变化范围为298～673K.利用Raman光谱和X射线光电子谱(XPS)对DLC薄膜的化学结合状态与衬底温度之间关系进行研究.薄膜XPS的C1s谱的解谱分析得出薄膜中含有sp³C(结合能为285.5eV)和sp²C(结合能为284.7eV)成分,根据解谱结果评价薄膜中sp³C含量.根据XPS分析可知,衬底温度低于473K时,sp³C的含量大约为40%左右;随着沉积薄膜时衬底温度的提高,sp³C的含量降低,由298K时的42.5%降到673K时的8.1%,从573K开始发生sp³C向sp²C转变.Raman光谱表明,随着衬底温度的提高,Raman谱中G峰的峰位靠近石墨峰位,G峰的半峰宽降低,D峰与G峰的强度比I_D/I_G增大,说明薄膜中的sp³C的含量随衬底温度增加而减少.     

Molecular orbital analysis of the XPS spectrum of a fluorine containing polyimide: PMDA–BDAF

The results of XPS measurements and molecular orbital calculations performed on the fluorine containing polyimide, PMDA–BDAF, are presented. The calculated carbon 1s (C1s) core energy level positions are compared with the level positions inferred from the XPS measurements. Within Koopman's approximation, the observed shape of the main XPS peak is consistent with the calculated distribution of C1s levels under this peak. Comparison of the magnitude of the carbonyl XPS peak intensity with the main peak intensity indicates a carbonyl C1s signal deficiency compared with that expected for “ideal bulk stoichiometry” i.e., for a polymer with no crosslinks or chain terminations. Comparison of data obtained from a grazing emission (surface sensitive) geometry with that obtained from a normal emission geometry, which probes more deeply into the bulk, indicates a signal enhancement of the C1s levels associated with carbon atoms of the CF₃ groups as one nears the polymer surface. Such enhancement might be due to either actual differences in chemical composition, or to preferential structural ordering near the polymer surface.     

Surface and in-depth characterization of TiC/C and Ti(C,N) layers by means of AES and Factor Analysis

Magnetron sputtered TiC/C multilayers and Plasma Vapour Deposited Ti(C,N) layers have been investigated by AES. The carbon sensivity factor has been calibrated for the correct composition of a TiC standard sample. Nitrogen has been measured indirectly based on the Ti(L3M23M23)/Ti(L3M23V) peak area ratio in the direct E.N(E) spectrum using Ti, TiC and TiN standard samples. The influence of Tougaard background removal has been tested. As the less accurate method taking the Ti peak-to-peak ratio has been found to give adequately good results. It has been possible to recalculate AES depth profiles, where only peak-to-peak values and no peak areas in the direct spectrum are available. Factor Analysis has been applied to AES depth profiling results. The data matrix in each column contains the linked experimental spectra of the measured elements. Based on the standard spectra the main components of a TiN layer on silicon have been identified by Factor Analysis. The structure of a TiC/C multilayer system has been resolved by the characteristic C(KLL) peak shape in C and TiC. Factor Analysis enables to calculate the individual profiles for Ti, TiC and C.     

Study of the first nucleation steps of thin films by XPS inelastic peak shape analysis

The initial steps in the formation of thin films have been investigated by analysis of the peak shape (both inelastic background and elastic contributions) of X‐ray photoelectron spectra. Surface coverage and averaged height of the deposited particles have been estimated for several overlayers (nanometre range) after successive deposition cycles. This study has permitted the assessment of the type of nucleation and growth mechanisms of the films. The experiments have been carried out in situ in the preparation chamber of an XPS spectrometer. To check the performance of the method, several materials (i.e. cerium oxide, vanadium oxide and cadmium sulfide) have been deposited on different substrates using a variety of preparation procedures (i.e. thermal evaporation, ion beam assisted deposition and plasma enhanced chemical vapour deposition). It is shown that the first deposited nuclei of the films are usually formed by three‐dimensional particles whose heights and degree of surface coverage depend on the chemical characteristics of the growing thin film and substrate materials, as well as the deposition procedure. It is concluded that XPS peak shape analysis can be satisfactorily used as a general method to characterize morphologically the first nanometric moieties that nucleate a thin film. Copyright © 2006 John Wiley & Sons, Ltd.     

XPS光电子峰和俄歇电子峰峰位表

在长期从事XPS分析测试的经验基础上,搜集了有关文献中的大量数据,编制了XPS光电子峰和俄歇电子峰峰位表,用于正确识别各种样品XPS谱图中的电子峰,达到快速、正确分析各种样品元素组成和化学组成的目的．本峰位表对于从事XPS测试的分析人员和应用XPS的科技人员具有很好的实用价值．     

Molecular orbital analysis of the XPS spectra of PMDA-ODA polymide and its polyamic acid precursor

The calculated carbon 1s (C1s) core energy-level positions of PMDA-ODA polymide and of its polyamic acid precursor are compared with the level positions inferred from XPS measurements. For the polyamic acid, calculation and experiment both yield a difference of approximately 1 eV between the carboxylic acid and the amide carbonyl C1s level positions. The difference in shape between the main C1s XPS peaks of the polyamic acid and polyimide is shown to be related to the difference in C1s core energy-level shifts of the carbon atoms composing the benzene ring adjacent to the amide or imide group. The planar imide or PMDA structure apparently yields larger core level shifts for these atoms. We have previously designated these atoms as “imide carbon atoms” (C-Im) to distinguish them from the aromatic carbon atoms (C-C) of the ODA part of the polymeric repeat unit. Comparison of the carbonyl XPS band intensities with the main peak intensities for the polyamic acid, as well as for the polyimide, suggests that there is a carbonyl deficiency at the surface of both of these materials.     

Determination of amount of substance for nanometre‐thin deposits: consistency between XPS,RBS and XRF quantification

Quantification on the nanometre scale is a key task in quality control and for the development of new materials in nanotechnology. In this paper we have studied the consistency in the determination of the amount of substance found by XPS peak shape analysis, Rutherford backscattering spectroscopy (RBS) and x‐ray fluorescence spectrometry (XRF). To this end, ZnO was deposited by plasma‐enhanced chemical vapour deposition on the three substrates. Four different sets of samples were produced, with the amount of ZnO deposited in the range 1–10 nm. From XPS analysis it is found that ZnO grows in the form of islands on all three substrates. For each system, the analysis was done independently with two XPS peaks from the overlayer with widely different kinetic energy and one XPS peak from the substrate. The growth mechanism found from analysis of each of the three peaks was consistent and the total amount of determined ZnO material was identical to within 15%. The root‐mean‐square deviation from the XPS quantification of the relative AOS was 20% for XRF and 16% for RBS. Because the absolute amount of substance determined from analysis of the three XPS peaks for each sample was consistent, it is concluded that the energy dependence of the applied inelastic mean free paths (taken here from the empirical TPP‐2M formula) is correct. It was found that the absolute amounts of substance determined by RBS and XRF are consistently factors of 2.1 and 1.5 lower than the that determined by XPS peak shape analysis. It is suggested that the main reason for this large discrepancy is inaccuracy in the applied ‘effective’ inelastic electron mean free path. Copyright © 2003 John Wiley & Sons, Ltd.     

Surface and in-depth characterization of TiC/C and Ti(C,N) layers by means of AES and Factor Analysis

Magnetron sputtered TiC/C multilayers and Plasma Vapour Deposited Ti(C,N) layers have been investigated by AES. The carbon sensivity factor has been calibrated for the correct composition of a TiC standard sample. Nitrogen has been measured indirectly based on the Ti_L3M23M23/Ti_L3M23V peak area ratio in the direct EN(E) spectrum using Ti, TiC and TiN standard samples. The influence of Tougaard background removal has been tested. As the less accurate method taking the Ti peak-to-peak ratio has been found to give adequately good results. It has been possible to recalculate AES depth profiles, where only peak-to-peak values and no peak areas in the direct spectrum are available. Factor Analysis has been applied to AES depth profiling results. The data matrix in each column contains the linked experimental spectra of the measured elements. Based on the standard spectra the main components of a TiN layer on silicon have been identified by Factor Analysis. The structure of a TiC/C multilayer system has been resolved by the characteristic C_KLL peak shape in C and TiC. Factor Analysis enables to calculate the individual profiles for Ti, TiC and C.     

Multivariate Auger Feature Imaging (MAFI) – a new approach towards chemical state identification of novel carbons in XPS imaging

The clear identification of allotropes and similar chemical states of carbon in XPS imaging can be made difficult because of the subtle differences observed in spectra, particularly when varying from sp² to sp³ hybridised carbon. By shifting focus from the commonly analysed C1s region in XPS spectra to the often ignored C KVV region, we utilise the so‐called D‐Parameter to identify different forms of carbon in a surface. When this methodology is applied to XPS imaging, the result is a powerful and unambiguous tool for the chemical state identification of carbon in XPS images. Further enhancement by multivariate statistics improves XPS spectral and image quality, and we call this technique Multivariate Auger Feature Imaging. Herein, we have applied this technique to clearly identify in XPS imaging a graphite film mounted on carbon tape. Copyright © 2015 John Wiley & Sons, Ltd.     

Processing and interpretation of core-electron XPS spectra of complex plasma-treated polyethylene-based surfaces using a theoretical peak model

Interpretation of X-ray photoelectron spectroscopy (XPS) spectra of complex material surfaces, such as those obtained after surface plasma treatment of polymers, is confined by the available references. The limited understanding of the chemical surface composition may impact the ability to determine suitable coupling chemistries used for surface decoration or assess surface-related properties like biocompatibility. In this work, XPS is used to investigate the chemical composition of various ultra-high-molecular-weight polyethylene (UHMWPE) surfaces. UHMWPE doped with α-tocopherol or functionalised by active screen plasma nitriding (ASPN) was investigated as a model system. Subsequently, a more complex combined system obtained by ASPN treatment of α-tocopherol doped UHMWPE was investigated. Through ab initio orbital calculations and by employing Koopmans' theorem, the core-electron binding energies (CEBEs) were evaluated for a substantial number of possible chemical functionalities positioned on PE-based model structures. The calculated ΔCEBEs showed to be in reasonable agreement with experimental reference data. The calculated ΔCEBEs were used to develop a material-specific peak model suitable for the interpretation of merged high-resolution C 1 s, N 1 s and O 1 s XPS spectra of PE-based materials. In contrast to conventional peak fitting, the presented approach allowed the distinction of functionality positioning (i.e. centred or end-chain) and evaluation of the long-range effects of the chemical functionalities on the PE carbon backbone. Altogether, a more detailed interpretation of the modified UHMWPE surfaces was achieved whilst reducing the need for manual input and personal bias introduced by the spectral analyst.