Nondestructive Depth Profiling

Main use Nondestructive depth profiling of thin films, crystal... 

Rutherford Backscattering (RBS) provides quantitative, nondestructive elemental depth profiles with depth resolutions sufficient to satisfy many requirements however, it is generally restricted to the analysis of elements heavier than those in the substrate. The major reason for considering depth profiling using FIXE is to remove this restrictive condition and provide quantitative, nondestructive depth profiles for all elements yielding detectable characteristic X rays (i.e.,Z> 5 for Si(Li) detectors). 

Nondestructive depth profiling and surface heterogeneity assessment using (1) photoelectrons with differing escape depths and (2) angular-dependent ESCA studies... 

As according to Eq. (25) the thermal diffusion length Ps is inversely proportional to the square root of the chopping frequency 00, nondestructive depth profiling is possible. 

Generally speaking, NRA is used in the same fields as the other IBA methods, PIXE and RBS, but their extension is needed down to the lighter elements (H, Li, B, C, N, O, F, and Na) and/or trace elements down to the level of 1-10 Xg/g. In such a way, NRA is complementary to PIXE (ion-y reactions) and RBS (ion-ion reactions). The excellent depth resolution (1-10 nm) for nondestructive depth profiling of some light nuclides, H, N, Na, and Al, is also exploited. 

RBS (Rutherford backscattering) 5 nm 0.1 mm quantitative quasi nondestructive depth profile... 

Rutherford backscattering is a valuable tool for getting quasi nondestructive depth profiles of thin films on surfaces. Due to their high primary energy, He " ions penetrate into solid surfaces up to ca. 1 pm and emerge back to the vacuum after a binary collision process with a target atom. This collision process follows Eq. (1-49) as ISS, which yields for 0=180° (backscattering)... 

Nondestructive depth profiling, which includes angle-resolved measurements, Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), peak intensity measurements from two or more peaks from the same element, and elemental intensity measurements as a function of incident electron energy (3)... 

In summary, CL can provide contactless and nondestructive analysis of a wide range of electronic properties of a variety of luminescent materials. Spatial resolution of less than 1 pm in the CL-SEM mode and detection limits of impurity concentrations down to 10 at/cm can be attained. CL depth profiling can be performed by varying the range of electron penetration that depends on the electron-beam energy the excitation depth can be varied from about 10 nm to several pm for electron-beam energies ranging between about 1 keV and 40 keV. 

Because a FIXE spectrum represents the int al of all the X rays created along the particle s path, a single FIXE measurement does not provide any depth profile information. All attempts to obtain general depth profiles using FIXE have involved multiple measurements that varied either the beam energy or the angle between the beam and the target, and have compared the results to those calculated for assumed elemental distributions. Frofiles measured in a few special cases surest that the depth resolution by nondestructive FIXE is only about 100 nm and that the absolute concentration values can have errors of 10-50%. 

When investigating opaque or transparent samples, where the laser light can penetrate the surface and be scattered into deeper regions, Raman light from these deeper zones also contributes to the collected signal and is of particular relevance with non-homogeneous samples, e.g., multilayer systems or blends. The above equation is only valid, if the beam is focused on the sample surface. Different considerations apply to confocal Raman spectroscopy, which is a very useful technique to probe (depth profile) samples below their surface. This nondestructive method is appropriate for studies on thin layers, inclusions and impurities buried within a matrix, and will be discussed below. 

Such features make SIMS a powerful technique for surface analysis. However, SIMS as a surface analysis technique has not yet reached a mature stage because it is still under development in both theoretical and experimental aspects. This lack of maturity is attributed to the complicated nature of secondary ion yield from a solid surface. Complexity of ion yield means that SIMS is less likely to be used for quantitative analysis because the intensity of secondary ions is not a simple function of chemical concentrations at the solid surface. SIMS can be either destructive or non-destructive to the surface being analyzed. The destructive type is called dynamic SIMS it is particularly useful for depth profiling of chemistry. The nondestructive type is called static SIMS. Both types of SIMS instruments are widely used for surface chemical examination. 

Neutron depth profiling has been applied in many areas of electronic materials research, as discussed here and in the references. The simplicity of the method and the interpretation of data are described. Major points to be made for NDP as an analytical technique include i) it is nondestructive il) isotopic concentrations are determined quantitatively iii) profiling measurements can be performed in essentially all solid materials, however depth resolution and depth of analysis are material dependent iv) NDP is capable of profiling across interfacial boundaries and v) there are few interferences. 

AES is not the same for all elements detected in the sample. Further, by varying the angle between the sample surface and analyzer, the sampling depth can be varied, resulting in a nondestructive quantitative concentration depth profile in the range 5 50 A. This feature is especially useful in XPS. 

Depth profile analysis using photothermal methods has contributed a number of nondestructive methods for studying the spectroscopy of plant tissues. The phase rotation method of signal recovery has been used to examine a number of specimens of botanical interest, including leaves, tissues, and lichens. 

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