Thin film multilayer systems

Barrier metals, as opposed to alloys like AuGeNi, are employed in many thin film metallization systems to promote adhesion and prevent interdiffusion. Gold is an excellent conductor, however, it has very poor adhesion to both Si and GaAs. Gold also shortens the device lifetime when it diffuses into an active region of the device. For this reason it is used in multilayered structures such as Ta/Pt/Ta/Au (50), W/Au (50) and Cr/Au (51). SIMS, AES and RBS have all been used effectively in studying metal-metal interdiffusion, to extract diffusion coefficients, and to estimate device lifetimes. 

Dry-chemistry immunoassay systems that require no liquid reagents and no sample pretreatment have also been developed for One system uses a thin-film multilayer... 

Table 2.4. Binary metal/metal systems observed to exhibit solid-state amorphiz-ation by interdiffusion or other type of driven mixing (e.g. mechanical codeformation). The table lists the type of experiment, the typical reaction temperature, TR (for the case of interdiffusion reaction) and references. (B thin-film bilayer diffusion couples, M thin-film multilayer diffusion couple, S interdiffusion of polycrystalline layer of one component with single crystal of another component, MA mechanical alloying of the metals, MAT thermal reaction of a mechanically deformed composite...

To reconcile experimental and theoretical observations on the size and temperature dependences of the elastic and plastic deformation of nanoscopic systems including atomic chains, NTs, liquid and solid skins, thin films, multilayers, nanocavities, nanograins, and nanocomposites to provide with consistent understanding. 

From optical point of view, an OLED structure can be considered as a multilayer thin-film system composed of absorbing and nonabsorbing materials, as shown in Figure 6.27. Therefore, the optical properties and optimal structure of such a multilayer device can be investigated by applying thin-film optical analysis techniques. Based on the theory of optical admittance analysis for analyzing the optical properties of a thin-film system [92], the optical properties of an OLED thin-film system can be simulated to reduce the ambient reflection. 

FIGURE 6.27 Schematic representation of an arbitrary multilayer thin-film system. 

The ability to apply a planarizing, optically transparent, thermally stable polymer system that cures under relatively mild conditions has recently been demonstrated to have utility in the fabrication of multilayer devices such as advanced color liquid-crystal display31,32 The ability to apply this material as a dielectric or optical coating for thin-film electronics devices has also recently been demonstrated with the fabrication of an optical wave guiding device.33... 

In actual experiments in biophysics, the interface may not be a simple interface between two media, but rather a stratified multilayer system. One example is the case of a biological membrane or lipid bilayer interposed between glass and aqueous media. Another example is a thin metal film coating, which quenches fluorescence within the first 10 nm of the surface... 

Fabrication of organic thin films based on sponfaneous molecular assembly has been considered as one of fhe powerful approaches to create novel supramolecular systems. In this context, multilayer films were fabricated by layer-by-layer electrostatic deposition techniques based on the electrostatic interaction between dsDNA and the positively charged polymer poly(diallyldimethylammonium chloride) (PDDA) on GC surfaces. A uniform assembly of PDDA/DNA multilayer films was achieved, based on the adsorption of the negatively charged DNA molecules on the positively charged substrate [55]. 

The main starting point for thin-fihn low molecular weight materials was the work reported by Ching W. Tang and Steven van Slyke of Kodak in 1987, when they described the green electrolnminescence obtained from a thin film of vapour deposited aluminium tris(8-hydroxyquinoline) (Alq). ° Since that time the development of multilayer device structures and several new important classes of organic EL materials has led to snbstantial improvements and to the commercial development of display technologies based on this system. ... 

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