This technical note outlines the properties and uses of the spherical mirror analyser (SMA) for XPS imaging and it's integration into a modern photoelectron spectrometer. It details the electron optical properties of the analyser for high energy and spatial resolution imaging.
Here we review the properties of the SMA including spatial and energy resolution and provide examples of the capabilities of such an imaging analyser. In the last few years the combination of the SMA with a two-dimensional, pulse counting electron detector has again increased the level of information available for surface characterisation. Generating such information requires the acquisition of multi-spectral datasets comprising a series of images incremented in energy so that each pixel contains photoelectron intensity as a function of energy. The datasets generated by this method contain >65,500 spectra and are therefore ideally suited to multivariate analysis to analyse the information content of the dataset and as a tool for noise reduction in individual images or spectra.
The performance of fluorinated textile treatment methods, in terms of wash resistance, was evaluated by XPS. Two different fluorination methods, solution based treatment and plasma polymer deposition, and four different textiles were studied with a view to producing long lasting, high performance clothing systems for outdoor activities. An important attribute of such textiles is the ability of the surface of the material to retain or regain its liquid repellent nature following conventional washing cycles.
XPS analysis revealed the degree of surface fluorination before and after wash cycles enabling the durability of the thin film coatings to be evaluated. Results indicated that for most materials the plasma polymer coated textiles exhibited better performance in terms of fluorine coverage and retention than the solution based fluorination metho
Typical samples are often presented for analysis following transportation in a less than ideal environment. This results in an analysis and measured surface composition that is not representative of the true surface of the original material. There are a limited number of methodologies available that can effectively clean the sample and restore the original surface without inducing some additional chemical changes and thereby changing the very surface that is being investigated. The development of Ar-gas cluster ion source has changed this.
In this study we apply the technique of depth profiling to analyse the concentration of elements in the near surface region of smart-phone display glass. We will look at the distribution of alkali and alkali earth metals - in particular K which is a key element in the glass toughening process. Two different depth profiling methods were used, monatomic Ar and Ar cluster, and a comparison is made regarding the ion bombardment effects of these two methods. We emphasise the importance of ion choice when depth profiling inorganic materials in particular those containing light alkali metals.
In this short study we will explore the differences in surface chemistry between two different graphites used in the nuclear industry. In recent times a wide variety of nanostructured carbon forms have been observed in nuclear graphite which vary the graphitic nature of the material. The nature of these forms can greatly affect the material’s ability to act as an effective moderator. Here we will discuss the elemental composition of the graphite surface and the extent of graphitic sp2 bonding.
Analysis of biomolecules on surfaces is essential to various applications of biosensors and biomolecule engineering. Matrix-assisted laser desorption/ionisation (MALDI) is now an established technique for mass spectrometry of biomolecules. Different matrix-analyte preparation protocols have been shown to influence the desorption or ablation process resulting in either high or low metastable fragmentation. It has been speculated that following laser ablation the velocities of the analyte and matrix can be regarded as a valuable and meaningful characteristic of the MALDI process. However, the interaction and distribution of the analyte with respect to the matrix is poorly understood. Here we study the distribution of a selection of biomolecules as a function of matrix material using high resolution imaging X-ray photoelectron spectroscopy (XPS).
An AXIS spectrometer was used to probe the surface chemistry of a widely used ionic liquid. The elemental surface composition was analysed and information was gained regarding the various chemical environments of the surface elements. Traditional surface analysis techniques such as ARXPS were exploited to determine the orientation of the mobile molecules in the uppermost layer of the liquid. The stability of the liquids under X-ray irradiation was also investigated.
XPS imaging is an important tool for investigating the lateral distribution of surface chemistry on the micron scale. Photoelectrons emitted from core electronic levels of surface atoms may be focused to form a two dimensional image on a suitable detector to allow the lateral distribution of the photoelectrons to be determined. AXIS spectrometers have a pulse counting delay line detector (DLD) system which allows images to be quantified. Spectra may be generated from every pixel in an image hence the chemical state of a sample surface may be quantitatively determined at high lateral and high energy resolution. In this example silicon dioxide particles dispersed on the surface of a silicon wafer were analysed to demonstrate the flexibility of XPS imaging.
Evaluation of Anti-Adhesive Coatings on Medical Textiles by XPS
XPS is a well-established method for the chemical characterisation of material surfaces. Key developments in recent years, including imaging, have resulted in a wider range of applications. Manufacturers and suppliers of both commercial and technical textiles are now exploiting XPS as an ideal tool to aid the development and optimisation of the types of surface coating/treatment demanded by industry and consumers.