Substrate surface

Due to the absorbed photon energy in the moment of the beam admission the particles and the substrate surface warm up very fast. As a consquence of the thermal induced stresses between the relative brittle hard particles, some particles brake apart and, because of the released impulse energy, they are ejected out of the effective beam zone, transmission... 

I.P.P.D and its relatives have become standard procedures for the characterization of the structure of both clean surfaces and those having an adsorbed layer. Somoijai and co-workers have tabulated thousands of LEED structures [75], for example. If an adsorbate is present, the substrate surface structure may be altered, or reconstructed, as illustrated in Fig. VIII-9 for the case of H atoms on a Ni(llO) surface. Beginning with the (experimentally) hypothetical case of (100) Ar surfaces. Burton and Jura [76] estimated theoretically the free energy for a surface transition from a (1 x 1) to a C(2x 1) structure as given by... 

The substrate is, of course, a necessary component of any SERS experiment. A wide variety of substrate surfaces have been prepared for SERS studies by an equally wide range of teclmiques [ ]. Two important substrates are electrocheniically prepared electrodes and colloidal surfaces (either deposited or in solution). 

A superlattice can be caused by adsorbates adopting a different periodicity than the substrate surface, or also by a reconstmction of the clean surface. In figure B 1.21.3 several superlattices that are conmionly detected on low-Miller-index surfaces are shown with their Wood notation. 

The first part is the headgroup, which is responsibie for the bonding to the substrate surface, which may be by chemisoriDtion or physisorjDtion. 

Figure C2.13.7. Change between polymerizing and etching conditions in a fluorocarbon plasma as detennined by tire fluorine-to-carbon ratio of chemically reactive species and tire bias voltage applied to tire substrate surface [36].

Fig. 1. The hthographic process. A substrate is coated with a photosensitive polymer film called a resist. A mask with transparent and opaque areas directs radiation to preselected regions of the resist film. Depending on resist characteristics, exposed or unexposed portions of the film are removed using a developer solvent. The resulting pattern is then transferred to the substrate surface and the resist is stripped.

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

Metallization layers are generally deposited either by CVD or by physical vapor deposition methods such as evaporation (qv) or sputtering. In recent years sputter deposition has become the predominant technique for aluminum metallization. Energetic ions are used to bombard a target such as soHd aluminum to release atoms that subsequentiy condense on the desired substrate surface. The quaUty of the deposited layers depends on the cleanliness and efficiency of the vacuum systems used in the process. The mass deposited per unit area can be calculated using the cosine law of deposition ... 

In electroless deposition, the substrate, prepared in the same manner as in electroplating (qv), is immersed in a solution containing the desired film components (see Electroless plating). The solutions generally used contain soluble nickel salts, hypophosphite, and organic compounds, and plating occurs by a spontaneous reduction of the metal ions by the hypophosphite at the substrate surface, which is presumed to catalyze the oxidation—reduction reaction. 

Cobalt—chromium films (20 at. % Cr) exhibiting strong perpendicular anisotropy, ie, hexagonal i -axis normal to the substrate surface, have been studied (53). Fifty nanometer films are composed of columnar crystaUites and the domain size was found to be a few stmctural columns in diameter. Magnetization reversal was shown to occur by domain rotation in thick films. Thinner (ca 10-nm thick) films do not show the columnar crystaUite... 

The material vaporized from a small area (point source) leaves the surface with a cosine distribution and thermal energies of a few tenths of an eV. The vaporized material arrives at a substrate surface having a mass per unit area dm dA) given by... 

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