Depth Profiling of Materials

Depth profiling of materials using variable-angle ATR spectroscopy is a well-established approach [50-53] that is based on the fact that the depth of penetration, dj, is a function of the angle of incidence in an ATR measurement The relationship between dp the wavelength of light, X, the refractive indices of the ATR crystal and the sample (wi and ri2, respectively) and the angle of incidence, 0, is shown in Equahon 10.1. 

Figure 14.34 Depth profile of material with a highly localized narrow region containing Cl. The high lateral resolution of Auger electron spectroscopy allows the characterization of thin layers and small features, such as this 100 A thick Cl-containing region. (From Weher.)...

It is well-known that the XPS measurements are useful to examine the depth profile of materials in the nm range. In Fig. 27.5, we showed experimental valence X-ray... 

Nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are part of the suit of ion beam analysis (IBA) techniques. They are commonly used for the elemental depth profiling of materials in a wide range of fields, e.g., from biological and medical to the semiconductor industry. 

Other approaches, close to the chemical ionization used in conventional mass spectrometry, use sample fiooding during the SIMS analysis or depth profiling. For instance, sample fiooding with NO gas upon depth profiling with Ceo alleviates the problem encountered in depth profiling of materials prone to cross-linking [344]. The reason is that NO react quickly with the free radicals created in the bombarded polymer surface, pre-... 

Three common uses of RBS analysis exist quantitative depth profiling, areal concentration measurements (atoms/cm ), and crystal quality and impurity lattice site analysis. Its primary application is quantitative depth profiling of semiconductor thin films and multilayered structures. It is also used to measure contaminants and to study crystal structures, also primarily in semiconductor materials. Other applications include depth profilii of polymers, high-T superconductors, optical coatings, and catalyst particles. ... 

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. 

Because of the complex nature of the discharge conditions, GD-OES is a comparative analytical method and standard reference materials must be used to establish a unique relationship between the measured line intensities and the elemental concentration. In quantitative bulk analysis, which has been developed to very high standards, calibration is performed with a set of calibration samples of composition similar to the unknown samples. Normally, a major element is used as reference and the internal standard method is applied. This approach is not generally applicable in depth-profile analysis, because the different layers encountered in a depth profile of ten comprise widely different types of material which means that a common reference element is not available. 

Neutron depth profiling technique (NDP) [13]. NDP is a speeial method for depth profiling of few light elements, namely He, Li, B and N in any solid material. The method makes use of speeifie nuelear reaetions of these elements with thermal neutrons. The samples are plaeed in the neutron beam from nuclear reactor and the charged products of the neutron indueed reactions (protons or alpha particles) are registered using a standard multiehannel spectrometer. From the measured energy spectra the depth profiles of above mentioned elements can be deduced by a simple computational procedure. 

SIMS and SNMS are versatile analytical techniques for the compositional characterization of solid surfaces and interfaces in materials research.92-94 As one of the most important applications, both surface analytical techniques allow depth profile analysis (concentration profile as a function of the depth analyzed) to be performed in materials science and the semiconductor industry with excellent depth resolution in the low nm range. For depth profiling in materials science, dynamic SIMS and SNMS using high primary ion beam doses are applied. Both techniques permit the analysis of light elements such as H, , C and N, which are difficult to measure with other analytical techniques. 

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