Materials science thick layers

Multilayer coatings of different composition and thickness are widely used in materials science and in the production of high-technology materials. The single- or multi-component thin layers significantly improve important characteristics of the materials with, e.g., specific properties. 

Ultramodern techniques are being applied to the study of corrosion thus a very recent initiative at Sandia Laboratories in America studied the corrosion of copper in air spiked with hydrogen sulphide by a form of combinatorial test, in which a protective coat of copper oxide was varied in thickness, and in parallel, the density of defects in the copper provoked by irradiation was also varied. Defects proved to be more influential than the thickness of the protective layer. This conclusion is valuable in preventing corrosion of copper conductors in advanced microcircuits. This set of experiments is typical of modern materials science, in that quite diverse themes... combinatorial methods, corrosion kinetics and irradiation damage... are simultaneously exploited. 

C. E. D. Chidsey, Science 251 919 (1991). Theory of electron transfer at gold covered by a thick layer of organic material. 

Lugovy, M., Orlovskaya, N., Berroth, K., Kuebler, J., Analysis of layered composite with crack deflection controlled by layer thickness, in Proceedings of NATO AST Functional Gradient Materials and Surface Layers Prepared by Fine Particle Technology, Kiev, Ukraine, 18-28 June 2000, ed. M.-I. Baraton and I. Uvarova, NATO Science Series, II, Mathematics, Physics and Chemistry, 16, Kluwer Academic Publishers, 273-280, 2001. 

This section will demonstrate the first sergeants and soldiers-type helix command surface experiment, in which thermo-driven chiroptical transfer and amplification in optically inactive polysilane film from grafted (or spin-coated) optically active helical polysilane onto quartz substrate [92]. Although helix and optical activity amplification phenomena based on the sergeants and soldiers principle was mainly investigated in polymer stereochemistry, the orientation and physical properties of a thick layer deposited onto a solid surface and controlled by a monolayer command film based on command surface principles was established in photochemical material and surface science [93,94]. Both sergeants and soldiers and command surface experiments appear to have been developed independently. 

Figure 2.18 Silicon dioxide thickness vs time of oxidation of 4H-SiC substrate with porous layer on it. Reproduced from S. Soloviev et al., Materials Science Forum, 389-393, 1113-1116. Copyright (2002), with permission from Trans Tech Publications...

The obtained patterned polymer surfaces can also be replicated by metal thermal evaporation to produce nanostructured metallic films with holes or asperities of controlled size, as illustrated in Fig. 11.10. After deposition of a sufficiently thick metal layer, the polymer layer can be cleaved or dissolved away. This procedure allows an efficient and precise control of the metallic surface structure, with possible applications in materials science and photonics. The roughness of polydimethylsiloxane (PDMS) surfaces can be tuned by this technique if the PDMS is treated while cross-linking, which may be of interest for microfluidic applications. We have also observed that substrates of poly(methyl methacrylate) (PMMA), PS in the form of colloidal spheres and bulk, and semiciystalline films of polyethylene (PE) are prrMie to be structured by this technique, evidencing the versatility and potential for its widespread use. It may find applications in many different scientific and technological fields like nanoUthography, microfluidics, or flexible electronics. 

FIGURE 36.9. Schematic view of a filler cluster of size f in elastomers, consisting of particles (primary aggregates) of size d. The glassy layer of immobilized polymer attached to the filler surface with characteristic thickness A is indicated. Reproduced from G. Heinrich, M. Kluppel and T. A. Vilgis, Current Opinion in Solid State and Materials Science 6 195-203 (2002) with permission from ELSEVIER. 

This method also enables the fabrication of the layered heterostructures comprising two (or more) organic materials (superstructures) with an accuracy of the monolayer thickness of the molecules. Of these, quantum-well type structures are expected to open up specific aspects in this new field of the materials science. 

Burnside, S., Winkel, S., Brooks, K., Shklover, V., Gratzel, M., Hinsch, A., Kinderman, R., Bradbury, G., Hagfeldt, A. Pettersson, H. (2000). Deposition and Characterization of Screen-Printed Porous Multi-layer Thick Film Structures from Semiconducting and Conducting Nanomaterials for use in Photovoltaic Devices. ]ournal of Materials Science Materials in Electronics, Vol. 11, pp. 355-362. 

The surface morphology of spray-dried emulsions was analysed by scanning electron microscopy (Hitachi S4800, Hitachi High-Technologies Corporation, Tokyo, Japan) at 3 kV and ambient temperature. Powder samples were deposited on aluminium SEM stubs coated with double-sided adhesive carbon tabs (Leit adhesive carbon tabs) and sputter coated with a layer of 6-7 nm thickness of gold. Fibrils were also characterised using atomic force microscopy (NanoWizard 3, JPK Instruments AG, BerUn, Deutschland) in cooperation with the Institute for Material Science, Kiel University. For details refer to Serfert et al. [56]. 

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