Ordered thin film

J. Teetsov and M.A. Fox, Photophysical characterization of dilute solution and ordered thin films of alkyl-substituted polyfluorenes, J. Mater. Chem., 9 2117-2122, 1999. 

Fet us start this section with real-time measurements of the crystallization process of highly ordered thin films of the molecular organic radical / -NPNN grown from the vapour phase on glass substrates (Caro et al, 2000). These films exhibit 2D... 

As discussed in Section 6.2.2, previously studied methods for electrodeposition of metal sulfide thin films involve either chemical reactions in solution to form solid particles (TS in water)42,43) or do not allow long-range homoepitaxial crystal growth (S in DMSO),37"",1) so are not suitable for deposition of ordered thin films of useful thickness. If a system where layer-by-layer... 

The existence of liquid crystals was first observed by Reinitzer [19] in 1888, but they were first classified and examined in a systematic way by Friedel [20] in 1922. Liquid crystals and their application to the formation of ordered thin films are discussed in Chapter 7. 

Atomic layer epitaxy (electrochemical) — Electrochemical atomic layer epitaxy (ECALE) is a self-limiting process for the formation of structurally well-ordered thin film materials. It was introduced by Stickney and coworkers [i] for the layer by layer growth of compound semiconductors (CdTe, etc.). Thin layers of compound semiconductors can be formed by alternating - underpotential deposition steps of the individual elements. The total number of steps determines the final thickness of the layer. Compared to flux-limited techniques... 

Valence photoelectron spectroscopy of sohd molecular materials requires highly ordered thin films, typically prepared by epitaxial film deposition. 

Early endeavours to obtain soluble, well-ordered thin films with good eleetrieal eonduetivity were not sueeessful. The reason was the wrong orientation of the moleeules with respeet to the substrate as well as the redueed ability to form well-ordered struetures in the solid film. Generally, the maximum eharge transport in TFT is realised in the direetion perpendieular to the plane of the thiophene rings due to the good 7i-7i-overlap favouring eleetron transport [1, 3]. 

We consider a typical thin-film configuration like that sketched in Fig. 5-5. We have already noted that any curvature of the boundaries will play no role in the leading-order thin-film (or lubrication) approximations provided that the radius of curvature is large compared with the gap width, and there is therefore no loss of generality in assuming one of the two surfaces to be flat. For convenience, we denote the coordinate perpendicular to this surface as z. The other boundary is also a solid surface of fixed shape, with the thickness of the fluid layer between them defined by the function, h( s. t), which can be expressed as a ftmction of the two spatial coordinates that lie in the plane parallel to the lower, flat wall, as well as a function of time. Because the most appropriate coordinate system will depend on the particular problem, it is convenient to maintain the symbolic representation of the... 

We seek an asymptotic solution of the leading-order thin-film equations, (5—134)— (5 136), in the form... 

Polymerization of mesogenic monomers is very effective for obtaining more stable ordered thin films. Triphenylene monomer containing acrylate moiety 18 was photopolymerized by UV light irradiation (Fig. 17). UV light was shone onto the mixture of the triphenylene derivative and a photoinitiator under inert atmosphere. Carrier transport characteristics of the ob-... 

For molecular van der Waals crystals of non-polar molecules, surface dipoles and work function anisotropy have only recently been explored [5], While variations of several tenths of an eV in the ionization energy (IE the molecular analog to a metal s <(>) depending on the molecular orientation on a surface have been reported several times [6-8], a consistent picture was lacking. An explanation for the intriguing observation that one and the same molecule can have different - still well-defined - IEs in ordered thin films is that the electrostatic potential above a molecular crystal surface is determined by the orientation of the molecules and their intramolecular charge distribution. 

Organic anions adsorbed on minerals can form well-ordered thin films, as shown by Fenter and Sturchio (1999) in an in situ X-ray reflectivity study of stearate on calcite. This paper demonstrated the use of X-ray reflectivity to characterize such thin films as well as to measure a sorption isotherm. There is great potential for using in situ X-ray reflectivity to investigate the interactions of organic ions and molecules with mineral surfaces. Further work in this direction has been pursued by Nagy et al. (2001) in a study of the adsorption of humic acids on muscovite, and by Fenter et al. (2001a) in a study of HEDP adsorption on barite. 

Polythiophene has been the subject of many diffraction studies. Several soluble, film-forming derivatives have been synthesized, and several oligomers and substituted model compounds have been obtained as single crystals or deposited as ordered thin films. This broad field will be covered in a separate contribution to this Handbook, written by Samuelsen and MIrdalen (.see chapter 2). For this reason, the current chapter does not contain a section on polythiophenes. 

Fluorescence quantum yields are summarized in Table 13.4 [28,38,152], a5T-a8T show quantum yields of < J0 in highly ordered thin films (d=3-5 nm) and around 1 order of magnitude higher values in thicker films. For the same thickness the yield is. smaller for more ordered films which is expected for molecules with strong excitonic coupling. Microcrystalline a4T has a yield of x i0 even in thin... 

Phthalocyanines and metallophthalocyanines have been intensively studied as discotic liquid crystals,but porphyrins have received less attention. The first examples of porphyrin discotic phases were based on naturally occurring uroporphyrins but showed a very narrow discotic LC range. However, octa—substituted porphyrins can show discotic meso-phases over a broad temperature range, the LC phase being stabilised by metal insertion into the porphyrin, e.g. zinc. These materials are organic semiconductors whose LC properties allow them to form highly ordered thin films in the solid state. Emission, excitation and absorption spectra in... 

The preparation of ordered thin films is of considerable interest in the construction of electronic devices and model membrane systems. A method that has gained much popularity in this area is the Langmuir-Blodgett (LB) technique [67]. The technique is based on the premise that molecules with a hydrophilic head and a hydrophobic tail can form a monolayer at an airwater interface and can be transferred onto a... 

Fig. 6.20 Chemical structures of 92-94 and schematic representation of their self-assemblies, which led to the formation of lamellar, ordered thin films through the stacking of the hydrogen bonded tapes...

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