Surface Analysis and Depth Profiling

A discussion of surface analysis requires a review of the depth being sampled during PA-FTIR spectroscopy. The depth being sampled during PA-FTIR analyses of rubbers is the thermal diffusion depth (Dt). This is a function of the thermal diffusivity of the sample, the wavenumber, and the mirror velocity. 

For illustrative purposes a thermal diffusivity of 1.3 x 10 3 cm2/s is often used as being typical of rubber and polymers. Some values from the literature for various materials are given in Table 2.1. Using the value of 1.3 x 10 3 it can be calculated that a depth of 3 to 11 Jim is being sampled at 2000 cm 1 as indicated in Table 2.2. This is an order of magnitude greater than that sampled by ATR techniques. 

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Figure 1. Three levels of analysis for catalyst materials, a) bulk analysis of an entire catalyst pellet, b) surface analysis and depth profiling from the surface inward, c) analytical electron microscopy of individual catalyst particles too small for analysis by other techniques.

Yang, C.Q. Bresee, R.R. Fateley, W.G. "Near Surface Analysis and Depth Profiling with FT-IR Photoacoustic Spectroscopy" Appl. Spectrosc., in press. 

Surface Analysis and Depth Profiling with SNMS... 

L MS has also potential for surface analysis and depth profiling. Zenobi et al [263] have described spatially resolved direct in situ analysis of polymer additives (Tinuvin PS/234/320/326/327/328/329/343, Lowinox 22, Santowhite) in POM, PVC, PP and PET using two-step CO2 laser X = 10.6 /xm) mass spectrometry (L MS). Under usual L MS experimental conditions it proved difficult to observe... 

Possibilities and limitations of EPMA techniques for quantitative near-surface analysis and depth profiling were described [259]. Spatial distributions... 

Davidson, C. M., N. J. Peters, A. Britton, et al. 2004. Surface Analysis and Depth Profiling of Corrosion Products Eormed in Lead Pipes Used to Supply Low Alkalinity Drinking Water. Water Science and Technology 49 49-54. 

Beam Effects, Surface Topography, and Depth Profiling in Surface Analysis (Methods of Surface Characterization), Czanderna, A. W Madey, T. E. Powell, C. J. eds.. Plenum Press New York,... 

Rutherford back-scattering spectroscopy (RBS) is one of the most frequently used techniques for quantitative analysis of composition, thickness, and depth profiles of thin solid films or solid samples near the surface region. It has been in use since the nineteen-sixties and has since evolved into a major materials-characterization technique. The number and range of applications are enormous. Because of its quantitative feature, RBS often serves as a standard for other techniques. 

The introduction of rfpowered sources has extended the capability of GD-OES to non-conductors, and several rf sources of different design have become commercially available. This is of the greatest importance for surface and depth-profile analysis, because there exists a multitude of technically and industrially important non-conductive coating materials (e. g. painted coatings and glasses) which are extremely difficult to analyze by any other technique. 

Applications Table 8.58 shows the main fields of application of inorganic mass spectrometry. Mass-spectrometric techniques find wide application in inorganic analysis, and are being used for the determination of elemental concentrations and of isotopic abundances for speciation and surface characterisation for imaging and depth profiling. Solid-state mass spectrometry is usable as a quantitative method only after calibration by standard samples. 

Secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS) are today the most important mass spectrometric techniques for surface analysis, especially for thin layer analysis, for depth profiling, for the determination of contaminations and element distribution on a solid sample surface. 

X-ray photoelectron spectroscopic(XPS) analysis with argon-etching gives surface and depth profile of catalyst composition[20]. Figure 2 shows enriched Te-content at surface of Te/Mo=... 

The transmission electron microscopy was done with a 100-kV accelerating potential (Hitachi 600). Powder samples were dispersed onto a carbon film on a Cu grid for TEM examination. The surface analysis techniques used, XPS and SIMS, were described earlier (7). X-ray photoelectron spectroscopy was done with a Du Pont 650 instrument and Mg K radiation (10 kV and 30 mA). The samples were held in a cup for XPS analysis. Secondary ion mass spectrometry and depth profiling was done with a modified 3M instrument that was equipped with an Extranuclear quadrupole mass spectrometer and used 2-kV Ne ions at a current density of 0.5 /zA/cm2. A low-energy electron flood gun was employed for charge compensation on these insulating samples. The secondary ions were detected at 90° from the primary ion direction. The powder was pressed into In foil for the SIMS work. 

The system depicted in Figure 4 contains the components for XPS analysis of the disk and ion depth profiling for the removal of surface films and polymer layers. X-rays are the excitation for the emission of electrons from the surface whose binding energies are measured with the analyzer. A beam of argon ions are directed at the surface in the location of analysis for depth profiling. 

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