Multilayer structures depth profiles

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. ... 

A multilayer-type structure probably due to cords in the molten zone between single arc sprayed (0.25 MPa) Ni droplets and steel substrate were found in AES point depth profiles [2.158]. That particular arc spraying condition turned out to yield the best adhesion. Plasma-sprayed AI2O3 layers separated from pre-oxidized Ni Substrate had a micrometer-thick NiO layer on the substrate-sided face and micrometer-deep oxide interdiffusion [2.159]. In this work also, AES point depth profiling substantiated technological assumptions about adhesion mechanisms. 

A certain relationship, which exists between the bulk and surface properties of semiconducting materials and their electrochemical behavior, enables, in principle, electrochemical measurements to be used to characterize these materials. Since 1960, when Dewald was the first to determine the donor concentration in a zinc oxide electrode using Mott-Schottky plots, differential capacity measurements have frequently been used for this purpose in several materials. If possible sources of errors that were discussed in Section III.3 are taken into account correctly, the capacity method enables one to determine the distribution of the doping impurity concentration over the surface" and, in combination with the layer-by-layer etching method, also into the specimen depth. The impurity concentration profile can be constructed by this method. It has recently been developed in greatest detail as applied to gallium arsenide crystals and multilayer structures. 

Utilizing an electrocopolymerization technique, various conducting copolymer layered structures were constructed. The copol)mier composition, and the thickness of the polymerized copolymer, are controlled easily in the electrolytic polymerization process (Fig. 7). Fig. 8 is an example of such depth profile-controlled multilayers, consisting of polypyrrole and copoly(pyrrole/3-methylthiophene). The present method will allow nm-level thickness control. 

Ninomiya, S., Ichiki, K., Yamada, H., Nakata, Y, Seki, T., Aoki, T., Matsuo, J. (2009) Molecular depth profiling of multilayer structures of organic semiconductor materials by secondary ion mass spectrometry with large argon cluster ion beams. Rapid Commun. Mass Spectrom., 23, 3264-3268. 

Muller F, Bimer A, Gosele U, Lehmann V, Ottow S, Foil H (2000) Structuring of macroporous silicon for applications as photonic crystals. J Porous Mater 7 201-204 Nassiopoulu AG, Kaltsas G (2000) Porous silicon as an effective material for thermal isolation on bulk crystalline silicon. Phys Stat Solidi (a) 182 307 Nava R, de la More MB, Taguena-Martinez J, del Rio JA (2009) Refractive index contrast in porous silicon multilayers. Phys Stat Solidi C6 1721-1724 Pettersson L, Hultman L, Arwin H (1998) Porosity depth profiling of thin porous silicon layers by variable angle spectroscopic ellipsometry a porosity graded layer model. Appl Optics 37(19) 4130 136... 

Depth profiles can be obtained retrospectively with ion imaging. Figure 4.30 is an illustration with a Si02-coated sample of an AlAs/GaAs multilayer structure with a locally-melted 4 pm laser stripe. The sample has 20 periods of 50-nm/50-nm... 

Generally, passive layers are not simple homogeneous oxide or hydroxide films. Usually, they have at least a bilayer or a multilayer structure, even for pure metal substrates. As already mentioned in Sec. 1.4.2 on surface analytical methods, oxides are located at the metal surface followed by an overlayer of hydroxide. Lower valency species are located inside, whereas higher valency cations are found in the outer parts of the films. In the case of alloys, very specific depth profiles are found which are related to the specific passive properties of these metals (Strehblow, 1997). The accumulation of one component relative to the other is a consequence of the thermodynamics of its anodic oxidation or its dissolution characteristics. As a consequence, one metal component may be accumulated at the metal surface, e.g., copper for AI/Cu (Strehblow et al., 1978) (Fig. 1-28) and copper for Cu/Ni alloys (Druska et al., 1996 Druska and Strehblow, 1996). The preferential dissolution of iron and the accumulation of Cr(III) within the film is another example (Fig. 1-27). 

Thus, the diffracted X-rays represent the structure within the top surface layers. A depth profile (z-profile) of the structure can be generated by inverting a sequence of scans at a series of incidence angles (r-profiles) [118]. GID experiments are carried out using an experimental arrangement similar to those of a related technique, reflectometry. Whereas the reflectometry measures the electron density variations normal to the surface from which parameters such as the surface thickness and the arrangement of different layers in multilayered surfaces can be examined [119,120], GID can be used to analyze the atomic and molecular structure near the surface. 

Murthy NS, Bednarczyk C, Minor H. Depth-profiles of structure in single-and multilayered commercial polymer films using grazing-incidence X-ray diffraction. Polymer 2000 41 277-284. 

AES sputter depth profile through an iron/copper/chromium multilayer structure. Each layer is 5 nm thick (Courtesy of Thermo Fisher Scientific)... 

The multilayer model of the passive film is the result of ARXPS studies combined to XPS and ISS depth profiles. The interpretation by a multilayered structure is not necessarily the only possibility. An alternative is a continuous change of the composition without phase... 

Intensive studies of lithium electrodes by impedance spectroscopy [25] and depth profiling by XPS [26,27] have clearly indicated the multilayer nature of the surface films formed on them. It is assumed that the inner part, close to the active metal, is compact, yet has a multilayer structure, and that the outer part facing the solution side is porous. Some evidence for this assumption was found by in situ imaging of lithium deposition-dissolution processes by atomic force microscopy (AFM) [28], There is also evidence that the inner part of the surface films is more inorganic in nature, comprised of... 

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