Information depth

The exit angle, /J, and the angle of incidence, a, of the beam (Fig. 3.63) determine the depth resolution and information depth. Small angles increase the depth resolution but reduce the depth probed. To optimize both quantities recoil angles 6 between 30 ° and 45 ° are often used, with a = /J = d/2. 

Technique Primary probe Elemental range Type of information Depth of information Lateral resolution Sensitivity (at. %) Ease of quantification Insulator analysis Destructive UHV environment... 

Among the techniques mentioned previously, XPS has the greatest impact on polymer surface analysis. A major additional source of chemical information from polymers comes from IR and Raman spectroscopy methods, These vibrational data can be obtained from the bulk and the surface region, although the information depth is much greater than with AES, XPS, or ISS. 

Method Exciting particle Detected particle Information depth (nm) Detection limit (at.%) Lateral resolution ( m) Range of elements Bond information Destruc- tibility... 

Mixing-Roughness-Information Depth (MRI) model, 24 100 Mixing systems, 26 669 Mixing tanks, distribution of solids in, 26 694... 

Clarke, F. C., Hammond, S. V., Jee, R. D. and Moffat, A. C. (2002) Determination of the information depth and sample size for the analysis of pharmaceutical materials using reflectance near-infrared microscopy. Appl. Spectrosc. 56, 1475-83. 

Transmission arrangements for SI applications follow the classical transmission layout, with a radiation source on one side of a sample and the SI analyser on the other side. The information depth is either constant or can easily be measured, which is an advantage in particular for (semi-)quantitative analysis. Although occasionally applied, such transmission systems suffer from the restriction that the sample must either be freely suspended or rest on a support that is transparent in the investigated spectral range. 

Elemental analysis of surfaces and films, high resolution (ca. 500 A) from top 1- to 20-A layer. Limited valence-state information. Depth profiling. 

Photo- and cathodoluminescence (PL, CL) measurements at liquid helium temperature are sensitive tools for investigation of the optical recombination properties [62] of the PLD ZnO films. In ZnO, the information depth of PL using a 325 nm He-Cd laser is only about 60 nm [63], corresponding to... 

As mentioned above, all metal surfaces used in these studies contain an oxidic layer and non-specifically adsorbed surface contaminations. Even the copper surface contains an oxidic layer in the order of 1-2 nm thickness. The differences in the adsorption capacities of a metal and its corresponding metal oxide towards PVFA-co-PVAm were compared by means of Zn and ZnO as well as Fe and Fe2C>3. XPS was employed in order to determine the amount of the polyelectrolyte adsorbed onto the metal or metal oxide surface. XPS is a well established surface sensitive spectroscopic method with an information depth not higher than 10 nm. 

Raman spectroscopy is a bulk technique, although the depth of the analyzed volume is limited. The information depth and thus the spectra depend on the excitation frequency and the absorption coefficient and crystallinity of the sample (Cardona, 1983). To characterize catalyst surfaces and their interactions with reactants, the spectral contributions from the surface have to be discriminated from those of the catalyst bulk. This complication has to be considered when applying Raman spectroscopy to working catalysts (Banares, 2005). 

Electron backscatter diffraction (EBSD) — The focused electron beam of Scanning Electron Microscopes (SEM) can be used to detect the crystallographic orientation of the top layers of a sample. The backscattered electrons (information depth 40-70 nm at 25 kV accelerating potential, lateral resolution around 200 nm) provide characteristic diffraction patterns (Kikuchi lines) on a phosphor screen. The patterns are recorded by a CCD-camera and interpreted by software. The position of the unit cell of the sample is determined by the corresponding Euler angles. In scanning mode, the software produces a surface orientation mapping that consists of... 

For longer treatment times (> 0.7 s) it has been shown (2) with the help of complementary surface techniques such as ISS (outermost layer sensitivity), Static SIMS (0.1-1 nm of information depth) and XPS (5 nm information depth), that the topmost surface layer is highly oxidized and that further chemical modifications occur beneath. The incorporation of both nitrogen and oxygen after a N2 plasma treatment have been evidenced by XPS whereas ISS did not reveal any trace of nitrogen (2). 

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