Composition Depth Profiling

Quantitative analysis of a depth profile, in addition to quantifying concentrations, needs to measure depth accurately. There are several factors we should be aware of for resolution of depth measurement. 

the etching rate for each type of atom is not constant even though the ion beam energy and ion density are exactly the same. The consequence of this phenomenon is that 

1 Explain why H and He cannot be detected by Auger electron spectroscopy. 

2 How many types of KLL Auger electrons are there Rank them according to their kinetic energies. 

4 Why are differential spectra preferred in AES analysis Why are direct spectra often used for quantitative analysis  

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AES Auger electron spectroscopy After the ejection of an electron by absorption of a photon, an atom stays behind as an unstable Ion, which relaxes by filling the hole with an electron from a higher shell. The energy released by this transition Is taken up by another electron, the Auger electron, which leaves the sample with an element-specific kinetic energy. Surface composition, depth profiles... 

In summary, the forte of SNMS is the measurement of accurate compositional depth profiles with high depth resolution through chemically complex thin-film structures. Current examples of systems amenable to SNMS are complex III-IV laser diode structures, semiconductor device metallizations, and magnetic read-write devices, as well as storage media. 

The data chain of the collected atoms can be converted to a one-dimensional composition-depth profile. The depth profile shows an average concentration of solute within the aperture, and there is always a possibility that the chemical information from the selected area is a convolution of more than one phase, as indicated diagrammatically in Figure 1.5, which represents the analysis of a FIM specimen containing second phase particles and also an interface across which there is a change of composition. 

Fig. 4.47 Equilibrium composition depth profiles of Ni-5% Cu and Pt-5% Au. For Ni—5% Cu the enrichment of Cu is confined to the top layer. The enrichment of Au in Pt-5% Au extends to 3 to 4 layers in depth and shows an oscillatory tail.

Some interesting features can be noticed in these lateral concentration profiles and composition depth profiles. For the Ni-5% Cu alloy, the first few ions detected are Cu ions, even though the composition within the top layer is rather uniform. This can be due to an edge effect, in other words the edges of the (111) layers are much more enriched with Cu atoms than inside the top (111) layer. This can also be simply produced by a preferential field evaporation of Cu atoms from the layer edges. While... 

Table 4.8 ToF atom-probe composition depth profiles in alloy segregation... 

Fig. 4.49 Composition depth profiles of the (001) plane of two Pt-44.8 at.% Rh alloys, one containing sulfur impurity and one not. Note the reversal of the enriched species, in both the top and the second layers.

XRD and grazing-incidence synchrotron radiation diffraction (GISRD) plots of a hybrid sample at different depths from the surface showed the abundance of a-Al203, AT and mullite to vary with depth (Fig. 5.13). As the depth increased, the abundance of both mullite and AT decreased, but that of aAl203 increased. The composition depth profiles as determined from the Rietveld analysis are shown in Fig. 5.13(a). From the results it can be seen... 

RBS provides a measure of composition-depth profile for elements. It uses a beam of high voltage helium ions to interact with the sample. The sample atoms recoil in a semi-classical collision, such that those ions reflected lose an amount of energy characteristic of the target atom and the amount of material traversed by the reflected ion. However, this method is not good for light elements such as H and He. 

Figure 7. Surface chemical composition—depth profile of Avothane. (O) Based on 1710 cm 1 based on 1600 cm 1, (a) The calibrated soft-segment content in air surface/substrate surface, (b) the calibrated silicone polymer content in air surface/substrate surface.

Figure 4. ERD-TOF results from a Corning Glass 0211 target (a) mass spectrum, (b) mass separated energy spectra superimposed by total energy spectrum, and (c) composite depth profile of the observed elements.

Figure 6.(a) Composite depth profile plot of a silicon nitride film on Si precoated with Si02. (b) "Hg ratio versus [NH3]/[SiH4] gas ratio for a-SixNyHz PECVD film from ERD, XPS and the deduction based on measured refractive-index. 

Figure 9. Composite depth profiles of Al, C, N and 0 from a target consisting of Al film on (a) dry and (b) hydrolized Kapton.

The composition depth profiles obtained from XPS data of the composition-ungraded and graded films in the case of a copper electrode used are given in Figure 21.5. 

Another range of matrix molecule sizes P=88-3173 was used in our study [251] on PI (polyisoprene, NA=114)-dPS (N=893) diblock copolymer segregating to interfaces created by polystyrene P-mer with vacuum and silicon substrate. The used PS molecular weights covers the wet and dry brush regime. In Fig. 40a we present typical composition-depth profiles of Pl-dPS obtained at the vacuum ( external ) interface of PS host matrix with P varied (P=88,495, and 3173), but constant bulk diblock concentration < )00=3.2(5)%. The surface peak and a related surface excess z (and coverage a) increases with P. This is even... 

Fig.40.a Composition-depth profiles of Pl-dPS (N=893) copolymer at the vacuum interface of different PS homopolymers (P).b The corresponding segregation isotherms [251]. Situations corresponding to different matrices are marked by O for P=88, for P=495 and V for P=3173 (results are insensitive to temperature modification [251])... 

Fig. 43.a Composition-depth profiles [251, 254] of PI(NA=114)-dPS diblock copolymers with various N-mer brush forming dPS blocks (N=89 (0),893 (A), and 9551 ( )) at the free surface of the high molecular weight P-mer (P>2.9 N) PS host matrix, b The corresponding segregation isotherms analyzed with mean field (solid lines, Eq. (67b) and self consistent mean field (SCMF, dashed lines) approaches, c Normalized interfacial segregation of dPS blocks z N/Rg(N) as a function of the normalized chemical potential of Eq. 68 [254]. The solid line shows the SCMF master curve [237]... 

Fig.44. Typical [255] composition-depth profiles of dPS blocks (after 3 days of annealing at 190 °C) in thin PS (m.w.=2.89X106) homopolymer films with binary mixtures of short and long copolymers. Deuterated short copolymers dS=PI(NA=114)-dPS(N=89) or their proto-nated analogs hS=PI (NA=143)-PS(N=124) as well as long deuterated dL=PI (NA=114)-dPS(N=9551) copolymers are used in pairs of samples with hS/dL (Q profiles) and dS/dL ( profiles) mixtures. The overall compositions of short (dS, hS) and long (dL) diblocks are 2.1 and 6.7% for (a) as well as 4.2 and 3.3% for (b), respectively...

In many systems, composition changes extend to a depth comparable to the range of the ion used for sputtering. The composition reaches a steady state after an amount of material comparable to the thickness of the altered surface layer has been sputter-removed. The steady-state surface composition is independent of the mass and energy of the sputtering ion. Composition depth profiles have been... 

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