XPS for chemical- and charge-sensitive analyses (original) (raw)
Related papers
Two-Dimensional X-ray Photoelectron Spectroscopy for Composite Surface Analysis
Analytical Chemistry, 2008
We describe a method for obtaining two-dimensional X-ray photoelectron spectroscopic data derived from the frequency dependence of the XPS peaks recorded under electrical square-wave pulses, which control and affect the binding energy positions via the electrical potentials developed as a result of charging. By using cross-correlations between various peaks, our technique enables us to elucidate electrical characteristics of surface structures of composite samples and bring out various correlations between hidden/overlapping peaks.
Surface and Interface Analysis, 2024
Strategies to deal with sample charging effects on X-ray photoelectron spectroscopy(XPS) spectra are presented. These strategies combine charge compensation (or lackof) via a flow of electrons and an electrical connection (or lack of) of samples to theground. Practical examples involving samples with a range of different electrical prop-erties, sample structure/composition and sensitivity to X-rays, illustrate the correla-tion between sample properties, measurement strategies, and the resulting XPS data.The most appropriate measurement strategy for a particular sample is also recom-mended. We highlight the crucial importance of appropriate XPS data acquisition toobtain a correct data interpretation
Analysis of surface structures using XPS with external stimuli
Surface Chemistry in Biomedical and Environmental Science
X-ray Photoelectron Spectroscopy, XPS, due to the perfect match of its probe length (1-10 nm) to nanoparticle size, chemical specificity, and susceptibility to electrical charges, is ideally suited for harvesting chemical, physical and electrical information from nanosized surface structures. In addition, by recording XPS spectra while applying external d.c. and /or pulsed voltage stimuli, it is also possible to control the extent of charging and extract various analytical information. In the simplest form, application of a static (d.c.) voltage stimuli enhances separation of otherwise overlapping peaks of gold nanoparticles from that of metallic gold. When the voltage stimuli is applied in the form of rectangular pulses, dynamic information is obtained from the frequency dependence of the charging shifts. This enables us to better probe the composition of nanoparticles produced (i.e. silicide formation, or whether or the extent of reduction, etc.) when platinum salt is deposited on silicon substrates. Finally, by recording the data in different time windows, XPS spectra can be recorded in time-resolved fashion. Time-resolved spectra can be used to detect, locate and quantify the charges developed in various surface structures like gold(core)/ silica(shell) nanoparticles on a copper substrate.
Recent developments in instrumentation for x-ray photoelectron spectroscopy
Analytical Chemistry, 1989
X-ray photoelectron spectroscopy (XPS or ESCA) is one of the many electron spectroscopies particularly useful for the chemical analysis of surfaces. The technique, based on the photoemission of electrons induced by soft X-rays, is widely used for detailed surface analytical problem solving hecause it allows multiple-element detection, provides chemical bonding and state information from chemical shifts, and provides quantitative information.
X-ray Photoelectron Spectroscopy
Journal of the Japan Society of Colour Material, 1991
X-ray photoelectron spectroscopy (XPS) is a non-destructive technique used to analyze the elemental compositions, chemical and electronic states of materials. XPS has a depth of analysis from 1 to 10nm. Chemical studies can be performed with more depth if surfaces are removed or etched. Samples need to be cleaned and free of surface
Electrical circuit modeling of surface structures for X-ray photoelectron spectroscopic measurements
2008
We model the X-ray photoelectron spectrometer and the sample with lumped electrical circuit elements, and simulate various types of conditions using a widely used computer program (PSpice) and compare the results with experimental measurements. By using the electrical model simulations, the surface voltage and the spectrum can be estimated under various types of external voltage stimuli, and the zero potential condition can be predicted accurately for obtaining a truly uncharged spectrum. Additionally, effects of several charging mechanisms (taking place during XPS measurements) on the surface potential could easily be assessed. Finally, the model enables us to find electrical properties, like resistance and capacitance of surface structures, under X-ray and low-energy electron exposure.
Bulletin of Materials Science, 1999
X-ray photoelectron spectroscopy (XPS) is one of the most powerful tools to characterize thin films materials. To illustrate the use of XPS, some examples will be given on materials used as positive electrode in microbatteries. Further analyses of the film to understand the redox process are quite difficult with conventional methods due to the amorphous nature of the cathode. Here surface methods fike XPS are very useful. Two main kinds of information can be obtained from XPS analysis: the oxidation states, and the determination of atomic environments. Different kinds of positive electrode materials were studied, titanium and molybdenum oxysulfides (MOyS,, M=Ti, Mo) and lithium cobalt oxide (LixCoOz+y) and have been illustrated in the present work. In light of the binding energies obtained for the reference compounds, several types of environments and different formal oxidation states have been found for the transition elements. XPS is also very useful for folllowing the oxydo-reduction mechanisms occurring during the intercalation and the de-intercalation of lithium, corresponding respectively to the discharge and the charge of the battery. After strict identification of each species, the evolution of their binding energies could be followed very easily. The XPS analyses of oxysulfides thin films at different stages of their cycling process have shown apparently good efficiency of the oxygen-rich compositions. During the redox process, the results obtained have clearly shown the important contribution of the sulfur atoms beside the transition metal atom.
XPS measurements for probing dynamics of charging
Journal of Electron Spectroscopy and Related Phenomena, 2010
The technique of recording X-ray photoemission data while the sample rod is subjected to ±10.0 V (dc) or square-wave pulses (ac) with varying frequencies in the range of 10 −3 to 10 3 Hz for probing charging/discharging dynamics of dielectric materials, is reviewed. Application of this technique introduces charging shifts as well as broadening of the peaks, which depend non-linearly on the polarity, as well as on the frequency of the pulses applied. These changes have been measured on: (i) an artificially created dielectric sample consisting of a Au metal strip connected externally to a series resistor of 1 M and a parallel capacitor of 56 nF, and two real dielectric films; (ii) a 20 nm organic polystyrene film spin-coated on a silicon substrate; (iii) a 10 nm SiO 2 inorganic layer thermally grown on silicon. A simple circuit model is introduced to simulate the charging shifts and the peak broadenings. Although this simple model faithfully reproduces the charging shifts in all three cases, and also some of the broadenings for the artificial dielectric and the polystyrene film, the additional broadening in the negatively charged peaks of the SiO 2 dielectric film cannot be accounted for. It is also claimed that these experimental findings can be used for extracting material-specific dielectric properties.