Characterizing layered structure

Since its introduction into the modem world of chemical analysis methods 1 K. Siegbahn, et al (1), photoelectron spectroscopy has become an increasingly important method for studying semiconductor surfaces. Not only is it widely emplc ed as a surface analytic method but also it finds wide application in chemically characterizing layered structures and interfaces which are important to semiconductor device manufacture. In this tutorial paper, a brief outline of the photoemission experiment will be presented. Modern instrumentation employed in semiconductor characterization will be surveyed and examples will be discussed which demonstrate the power of photoelectron spectroscopy in characterizing semiconductors and semiconductor device structures. 

The surface dividing the components of the mixture formed by a layer of surfactant characterizes the structure of the mixture on a mesoscopic length scale. This interface is described by its global properties such as the surface area, the Euler characteristic or genus, distribution of normal vectors, or in more detail by its local properties such as the mean and Gaussian curvatures. 

Crystallization of 5 in the open air from an initially aprotic solvent (N,N-dimethyl-acetamide) led to a non-layered structure which is characterized by a three-dimensional lattice of loosely-packed host species interspaced by channel-type zones accommodating the solvent guest components (Fig. 9). 

The combination of different analytical techniques offers the possibility for a complete characterization of building materials impregnated with liquid alkyl-alkoxysilanes RSi(OC2H5)3. The results derived from IR, NMR and SIMS spectra can be summarized in the schematic layer structure shown in Figure 5. 

In characterizing layered silicate, including layered titanate (HTO), the surface charge density is particularly important because it determines the interlayer structure of the intercalants as well as the cation exchange capacity (CEC). Lagaly proposed a method of calculation consisting of total elemental analysis and the dimensions of the unit cell [15] ... 

Before fluorination, the dielectric constant ofpoly(bisbenzocyclobutene) was 2.8, and this value was reduced to 2.1 after plasma treatment. No data were reported in the paper on characterization of structure or properties, except for the dielectric constant of the modified poly(bisbenzocyclobutene). The authors did report that the thermal stability offluorinatedpoly(vinylidenefluoride) was inferior to the original poly(vinylidenefluoride) when treated in a similar way. One of the probable reasons for the low thermal stability is that the NF3 plasma degraded the polymer. According to their results, the thickness of fluorinated poly(bisbenzo-cyclobutene) was reduced by 30%. The same phenomenon was observed for other hydrocarbon polymers subjected to the NF3 plasma process. A remaining question is whether plasma treatment can modify more than a thin surface layer of the cured polymer Additionally, one of the side products generated was hydrogen fluoride, which is a serious drawback to this approach. 

Microstructures of CLs vary depending on applicable solvenf, particle sizes of primary carbon powders, ionomer cluster size, temperafure, wetting properties of carbon materials, and composition of the CL ink. These factors determine the complex interactions between Pt/carbon particles, ionomer molecules, and solvent molecules, which control the catalyst layer formation process. The choice of a dispersion medium determines whefher fhe ionomer is to be found in solubilized, colloidal, or precipitated forms. This influences fhe microsfrucfure and fhe pore size disfribution of the CL. i It is vital to understand the conditions under which the ionomer is able to penetrate into primary pores inside agglomerates. Another challenge is to characterize the structure of the ionomer phase in the secondary void spaces between agglomerates and obtain the effective proton conductivity of the layer. 

Time-resolved techniques are very powerful for examining structures where the useful information is contained in the normally reflected signal. Frequency analysis of a reflected broadband signal can also be used for film characterization (Wang and Tsai 1984 Lee et al. 1985). But in many other problems, especially in materials science, there is a great deal of information contained in the way that the coefficient of reflection changes with angle of incidence. It is therefore important to understand the behaviour of the reflectance function R(d) of a layered structure. 

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