Composition lateral profile

This area of research is still at its beginning and many aspects are not resolved. This includes in particular the structure and conformation of polymers at an interface as well as the modification of polymer dynamics by the interface. We have given several examples of the potential of surface and interface analytical techniques. They provide information on surface roughness, surface composition, lateral structure, depth profiles, surface-induced order and interfacial mixing of polymers on a molecular and sometimes subnanometer scale. They thus offer a large variety of possible surface and interface studies which will help in the understanding of polymer structure and dynamics as it is modified by the influence... 

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... 

Peled E., Bar Tow D., Merson A., Gladkich A., Burstein L., Golodnitsky D. Composition, depth profiles and lateral distribution of materials in the SEI built on HOPG ToF-SIMS and XPS studies, J. Power Sources 2001, 97-98, 52-57. 

The physical techniques used in IC analysis all employ some type of primary analytical beam to irradiate a substrate and interact with the substrate s physical or chemical properties, producing a secondary effect that is measured and interpreted. The three most commonly used analytical beams are electron, ion, and photon x-ray beams. Each combination of primary irradiation and secondary effect defines a specific analytical technique. The IC substrate properties that are most frequendy analyzed include size, elemental and compositional identification, topology, morphology, lateral and depth resolution of surface features or implantation profiles, and film thickness and conformance. A summary of commonly used analytical techniques for VLSI technology can be found in Table 3. 

The disadvantage of lasers with nanosecond-picosecond pulse duration for depth profiling is the predominantly thermal character of the ablation process [4.229]. For metals the irradiated spot is melted and much of the material is evaporated from the melt. The melting of the sample causes modification and mixing of different layers followed by changes of phase composition during material evaporation (preferential volatilization) and bulk re-solidification [4.230] this reduces the lateral and depth resolution of LA-based techniques. 

Later on Cahn and Hilliard presented some thermodynamic estimates for the nucleation of liquid in vapour. Values of AO and the composition profiles c(r) of the embryos have been estimated using the mean-field and gradient expansion approximations for the free energy functional F c(7 ). A number of qualitative features in variation... 

Dynamic SIMS is used for depth profile analysis of mainly inorganic samples. The objective is to measure the distribution of a certain compound as a function of depth. At best the resolution in this direction is < 1 nm, that is, considerably better than the lateral resolution. Depth profiling of semiconductors is used, for example, to monitor trace level elements or to measure the sharpness of the interface between two layers of different composition. For glass it is of interest to investigate slow processes such as corrosion, and small particle analyses include environmental samples contaminated by radioisotopes and isotope characterization in extraterrestrial dust. 

Fig. 4.46 Lateral composition profile obtained for a Ni-5% Cu annealed at 550°C. The first few ions detected are Cu. This may indicate an edge effect, or simply preferential field evaporation of Cu from plane edges of Cu atoms.

Prescott, Hudson, Foner, and Avery (60) extended the mass-spectrographic technique to the study of composition profiles across a low-pressure, propane-air flame under somewhat lean conditions. The appearance and disappearance of hydrogen, carbon monoxide, ethylene, and acetylene in the flame were demonstrated clearly. The proportion of acetylene was not high. Nonetheless, it is evident that the formation of acetylene is not just a result of pyrolysis of excess hydrocarbon by heat released in combustion of part of the gas. It is a result of reactions which must occur to some extent in all hydrocarbon combustion, but which would not be observable except by special techniques, or under conditions—such as rich flames or cool flames—where the later reactions of acetylene can l>e minimized. 

The effective local temperatures in both sites were determined. By combining the relative sonochemical reaction rates for equation 5 with the known temperature behavior of these reactions, the conditions present during cavity collapse could then be calculated. The effective temperature of these hotspots was measured at 5200 K in the gas-phase reaction zone and 1900 K in the initially liquid zone (6). Of course, the comparative rate data represent only a composite temperature during the collapse, the temperature has a highly dynamic profile, as well as a spatial temperature gradient. This two-site model has been confirmed with other reactions (27,28) and alternative measurements of local temperatures by sonoluminescence are consistent (7), as discussed later. 

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