Mica film fabrication

In the past, mica has been the material of choice for the interacting surfaces because of the ease of handling and since molecularly smooth surfaces can be fabricated mica surface coated with a thin film of other materials (e.g., lipid monolayers or bilayers, metal films, polymer films, or other macromolecules such as proteins) can also be used. The use of alternative materials such as molecularly smooth sapphire and silica sheets and carbon and metal oxide surfaces is also being explored. 

A typical method for fabricating multiple complex layers is illustrated in Figure 2.11,12 First, an Au/mica or Au/ITO plate is immersed in a chloroform solution of tpy-AB-SS-AB-tpy (tpy=2,2 6, 2" -terpyridyl), providing Au-S-AB-tpy SAM on the plate. In the case of connecting the Fe(II) ion, the tpy-terminated plate is immersed in 0.1 M Fe(BF4)2 aq or (NH4)2Fe(S04)2 aq to form a metal complex. Subsequently, the metal-terminated surface is immersed in a chloroform solution of the ligand Lj or L2 to form a bis(tpy)iron structure (Fig. 2b). The latter two processes are repeated for the preparation of multilayered bis(tpy)iron (II) complex films with linear structures. When L3 is used instead of Lj or L2, the resulting molecular wires have a dendritic structure (Fig. 2c). 

Most SECM measurements are carried out with the sample under a thick liquid layer, and thus the tip must be sheathed in an insulator to achieve high resolution. SECM measurements can also be carried out within a thin layer of water that forms on the surface of a sample in air. In this case very high resolution can be attained using tips without insulation (e.g., the usual W or Pt-Ir STM-type tips) because the tip area is defined by the small part of the tip that touches the liquid layer (34,35). Studies of mica surfaces, polymer films, and some biological samples as described below are possible by this technique. With this mode it is also possible to fabricate small metal structures in polymer films as demonstrated previously (36). High-resolution electrochemical deposition of silver nanostructures on mica surfaces in humid air was also achieved (35). For detailed discussion on SECM applications for fabrication, see Chapter 13. 

Rubrene thin films were evaporated by HWE on mica. After the formation of an amorphous matrix, spherulite structures start to grow, which finally cover the whole surface. Due to their polycrystalline property the spherulites are resistant against oxidization while the amorphous matrix becomes transparent upon exposure to air, which is a clear sign for oxidation. The mbrene spherulites provide therefore a promising material for the fabrication of OFETs. 

Zhang and Mu [53] reported a new approach to fabricate the GdS thin films by annealing the Cd " "-dithiol multilayer films on both quartz and mica substrates and characterized the change of the composition, structure, and optical properties of the films before and after annealing. It opens up the possibility to fabricate the chalcogenide thin films by annealing the self-assembled multilayer films of metaUic ion and organic dithiol [53]. 

Block copolymers are also cast or spin coated for evaluation by a range of techniques, and these are discussed later in this chapter (see Section 5.3.4.6). Chen and Thomas [113] used force modulation microscopy (FMM), a SPM technique that measures relative elasticity across a surface, to study the block copolymer morphology of roll cast and spin coated films. Three model samples were investigated unannealed poly(styrene-butadiene-styrene) triblock copolymer, fabricated from solution using roll casting, cut perpendicular to the oriented cylinders with a razor blade annealed and unannealed poly(styrene-h-methyl methacrylate diblock copolymer spin coated from solution and an ultrathin film of a rod-coil diblock copolymer cast from a dilute solution onto a carbon coated mica sheet. Triblock copolymers were strained in tension using a copper grid as support and... 

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