Sharpness of the interface

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. 

Until recently, very little quantitative information was available on blends of block copolymers. The literature is summarized in Table 6.3. Hoffman et al. (1970) reported microscopic demixing of blends of PS-PB diblocks, with two maxima in the domain size distribution, but with no evidence tor macrophase separation. These findings must be treated with caution in the light of more recent results. Hadziioannou and Skoulios (1982) used SAXS and SANS to investigate the morphology of binary blends of PS-PI diblocks, and binary PS-PI/PS-PI-PS or PS-PI/PI-PS-PI blends or blends of the two types of triblock. They found that the blends were microphase separated, and that the sharpness of the interface was not reduced in blends compared to neat copolymers. The transition between a lamellar and a cylindrical structure was shown to depend primarily on blend composition. In contrast, the transition from a lamellar to a disordered phase at... 

The amplitude of the fringes also yields information about the sharpness of the interfaces in question, since large fringes correspond to a sharp interface, while small fringes are indicative of a diffuse interface. 

A of material, so that the sharpness of the interface also implies that there is little roughness of the interface. 

Particle morphology can be studied by fluorescence quenching if individual components of the particles can be labelled by covalent attachment of an appropriate dye [84]. The use of a fluorescence quencher to decrease the particle fluorescence intensity served to probe the interphase zone formation or the sharpness of the interface between polymer phases in the particles. 

If the interface is not sharp, but is characterized by a certain spatial profile of the dielectric constant of a given medium, e z), the ellipticity coefficient p is finite at the Brewster angle. In this case, the Brewster angle is defined as the angle, where the phase shift of the p-polarized wave is n/2. The value of the ellipticity coefficient at the Brewster angle therefore carries information about the sharpness of the interface. As we can measure this value very precisely, we can determine the parameters of the spatial profile of the dielectric constant with great precision. 

This is realized as the sputtering front follows the initial surface topography. If this is not parallel to any subsurface interface or feature/s of interest, the apparent sharpness of the interface/feature/s will be a convolution of both the surface topography and the abrnptness of the interface/feature. These effects, referred to as crater base effects within this text, are covered in Section S.3.2.4.3. 

The quality of a multilayer structure can be checked in several ways, but the most straightforward is cross-sectional TEM (XTEM). On an XTEM image the flatness of the layers and also the sharpness of the interfaces can be visualized. Figure 1 shows the XTEM image of the sample containing sets of 15 alternate layers of 2-nm-thick germanium and silicon, separated by layers of 10-nm-thick silicon. The interfaces are sharp and the layers are flat. The interface thickness can be estimated to be about 0.8 nm. 

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