Multilayered rough surfaces

Then a very thin barrier layer and a copper seed layer are formed (Figs. 21 (b) and 21 (c)>). In order to conduct the electric current, good conductive material, e.g., copper, will be coated on the surface of the copper seed layer which forms a rough surface as shown in Fig. 21(d). Since multilayer s introduction into IC production, the surface coated with copper must be very smooth, clean, and bare of dielectric stacks... 

Pfeifer, P. Wu, Q. Cole, C.W. Krim, J. (1989) Multilayer adsorption on a fractally rough surface. Phys. Rev. Letters 62 1997-2000... 

To realize second-order anisotropy, the atomic environment of the transition-metal atoms must have a sufficiently low symmetry [49, 62-65]. Figure 6 illustrates that this is often, but not always, the case for surface atoms. Magnetic surface anisotropy, first analyzed by Neel [62], is important in complicated structures and morphologies such as ultrathin transition-metal films [66], multilayers [67], rough surfaces [65], small... 

Other investigators, including Pfeifer and Obert (1989), Pfeifer et al. (1990), Krim and Panella (1991), Panella and Krim (1994) and Neimark and Unger (1993), have also studied multilayer adsorption on fractally rough surfaces. In particular, Pfeifer and his co-workers point out that the interpretation of a fractal dimension of a porous surface... 

Pfeifer P, Wu YJ, Cole MW, et al. Multilayer adsorption on a fraclally rough surface. Hiys Rev Lett 1989 62 1997-2000. 

Merely detecting a Raman signal from a solid substrate surface does not necessarily mean that SERS is in effect. Weak signals can be detected due to the improved Raman systems, the larger surface areas on rough surfaces, multilayer formations, and simple reflectivity considerations. 

The other area of rapid progress is in the development of theories and computational tools with which to interpret spectroscopic results for rough surfaces, discontinuous layers and multilayered heterostructures. 

Mitsas CL, Siapkas DI (1995) Generalized matrix method for analysis of coherent and incoherent reflectance and transmittanee of multilayer struetures with rough surfaces, interfaces and finite substrates. Appl Opt 34(10) 1678-1683... 

Another crucial problem is a proper account for the surface roughness and microporosity, which are inherent to a large number of novel polymer-templated silica and organosilica materials, such as, e.g. SBA-15 [11-14]. For many structures, especially those synthesized at low temperatures, the micropore volume cannot be reliably estimated from the comparison plot due to a competition between micropore filling and multilayer adsorption on the rough surface. 

Application of LbL in different fields of nanotechnology has led to the use of various types of porous and rough surfaces for multilayer growth. One significant use has been foimd in the field of separation science, that is, development of filtration membranes by modifying the surface of the porous membrane support to improve separation performance and antifouling properties. Some examples of such porous membrane support materials are polyethersulfone (PES) ultrafiltration membranes, polyacrylonitrile (PAN) ultrafiltration membranes, membrane of PAN with acrylic acid s ments (poly(acrylonitrile-co-acrylic acdd), porous polyacrylonitrile/ polyethylene terephthalate (PAN/PET) substrates, cellulose acetate membranes, porous ceramic supports, and porous alumina supports. The multilayer materials used for such modifications are listed, but not limited to, common polyelearolytes used for LbL applications, such as PSS, PAH, PDADMAC, PAA, and poly(vinyl sulfate) (PVS) copolymers such as poly(4-styrenesulfonic acid-co-maleic acid) quaternary ammonium salts such as cetyl trimethyl ammonium chloride and tetramethyl ammonium chloride as cationic species or nanoparticles such as Ti02. 

Many grades of interlayer are produced to meet specific length, width, adhesion, stiffness, surface roughness, color (93,94), and other requirements of the laminator and end use. Sheet can be suppHed with vinyl alcohol content from 15 to about 23 wt %, depending on the suppHer and appHcation. A common interlayer thickness for automobile windshields is 0.76 mm, but interlayer used for architectural or aircraft glaring appHcations, for example, may be much thinner or thicker. There are also special grades to bond rear-view mirrors to windshields (95,96) and to adhere the components of solar cells (97,98). Multilayer coextmded sheet, each component of which provides a separate property not possible in monolithic sheet, can also be made (99—101). 

Equations la and lb are for a simple two-phase system such as the air-bulk solid interface. Real materials aren t so simple. They have natural oxides and surface roughness, and consist of deposited or grown multilayered structures in many cases. In these cases each layer and interface can be represented by a 2 x 2 matrix (for isotropic materials), and the overall reflection properties can be calculated by matrix multiplication. The resulting algebraic equations are too complex to invert, and a major consequence is that regression analysis must be used to determine the system s physical parameters. ... 

TEM micrographs of a neat PS particle (a) and those coated with one to five Si02/PDAD-MAC multilayers (b-f). The nncoated PS latices are spherical and feature a smooth surface (a). The presence of SiOi/PDADMAC mnltilayers on the PS latices result in both an increase in surface roughness (dne to SiOi) and a systematic increase in the diameter of the PS latices (b-f). Consistent with the SPLS and SEM measnrements, the PS particles are homogeneously coated with nanoparticles. The TEM data (Fig. 6) yield an average diame-... 

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