Film preparation, electron

Alternative Thin-Film Fabrication Approaches. Thin films of electronic ceramic materials have also been prepared by sputtering, electron beam evaporation, laser ablation, chemical beam deposition, and chemical vapor deposition (CVD). In the sputtering process, targets may be metal... 

Glad [37] studied the micro deformations of thin films prepared from DGE-BA/MDA by electron microscopy. His results are also shown in Fig. 7.5. The deformation of the sample with high strand density was small and consequently its image in the EM rather blurred. Therefore, the result on Mc = 0.5 kg/mol should perhaps have been omitted. 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

Compounds that are radioactive can be located on a preparative layer by contact film autoradiography, electronic autoradiography, and storage phosphor screen imaging [21-23]. These methods differ in terms of factors such as simplicity, speed, sensitivity, and resolution, and the method of choice depends on the available equipment, reagents, and instrumentation. All are nondestructive, and the detected compounds can be recovered without change for later studies. 

Table IV shows X-ray data (55) on the homogeneity of Pd-Ag films prepared by simultaneous evaporation from separate sources, either in conventional vacuum or in UHV, with the substrate maintained at 0°C. The second group of films was prepared using a stainless steel system incorporating a large (100 1/sec) getter-ion pump, sorption trap, etc., but deposited inside a glass vessel. By the tests of homogeneity adopted, alloy films evaporated in conventional vacuum were not satisfactory, i.e., the lattice constants were generally outside the limits of the experimental error, 0.004 A, and the X-ray line profiles were not always symmetrical. In contrast, alloy films evaporated in UHV were satisfactorily homogeneous. Further, electron micrographs showed that these latter films were reasonably unsintered and thus, this method provides clean Pd-Ag alloy films with the required characteristics for surface studies.

There is now available a substantial amount of information on the principles and techniques involved in preparing evaporated alloy films suitable for adsorption or catalytic work, although some preparative methods, e.g., vapor quenching, used in other research fields have not yet been adopted. Alloy films have been characterized with respect to bulk properties, e.g., uniformity of composition, phase separation, crystallite orientation, and surface areas have been measured. Direct quantitative measurements of surface composition have not been made on alloy films prepared for catalytic studies, but techniques, e.g., Auger electron spectroscopy, are available. 

An overview of the precursors, process chemistry, and relative advantages and disadvantages of the three principal methods of inorganic electronic thin film preparation is shown in Table 2.1. Generally, sol-gel methods offer the greatest control over the nature of the solution precursor species, but they have involved... 

The above methods represent the most commonly employed methods for inorganic electronic thin film preparation. A variety of other methods, including Pechini,21 citrate,86 nitrate,23 and aqueous processes87 have also been used. For a discussion of these methods, the reader is referred to Refs. 5 through 12, which highlight these methods for the preparation of various electronic ceramic materials. 

The number of publications concerning utilization of the EISA process for fabrication of different structured materials is counted in the hundreds, which is far beyond the possibilities of this chapter to review in depth. Rather, we intend to provide a brief introduction into EISA and its application to the fabrication of functional thin films for electronic applications (e.g., electro-chromic layers and solar cells), with a special focus on fabrication of crystalline mesoporous films of metal oxides. Attention will also be given to techniques used to evaluate the pore structure of the thin films. For the other aspects of the EISA process, for example its mechanism,4 strategies for preparation of crystalline porous metal oxides,5 mesoporous nanohybrid materials,6 periodic organic silica materials,7,8 or postgrafting functionalization of mesoporous framework,9 we kindly recommend the reader to refer to the referenced comprehensive reviews. 

Titania films prepared by the methods described above are, however, just partially crystalline. Although WAXS patterns indicate formation of anatase crystals of ca. 10-12nm in size (Fig. 9.3a), the electron microscopy study demonstrates that the elongated crystals are actually embedded into an amorphous mesoporous matrix (Fig. 9.3c). The degree of crystallinity for such films usually does not exceed 60% attempts to increase it by calcination at higher temperatures cause uncontrolled crystal growth, which leads to collapse of mesoporos-ity and a drastic decrease in the surface area (Fig. 9.3d). 

Figure 9.5. Mesoporous Ti02 films templated by the KLE block copolymer, (a) Scanning electron microscopy (T = 600 °C, i.e., above the crystallization temperature) and (b) Krypton physisorption of films heat-treated at 570 °C (filled circles) and 650 °C (triangles). It is seen that the porosity of films, prepared by the advanced block copolymer template, is still intact even after treatment at temperatures that convert the amorphous Ti02 matrix into the crystalline (anatase) one. The films were prepared based on the recipe in Ref. 80.

Monodisperse analogs of such ir-electron systems, PPV oligomers (molecular glasses) were studied by Bazan and coworkers [217]. The films prepared from 192 by solution casting showed completely amorphous structure due to a tetrahedral structure of the molecule and OLEDs ITO/PVK/192/Al-emitted green light with an efficiency up to 0.22 cd/A (Chart 2.42). 

R. Banerjee and D. Das, Properties of tin oxide films prepared by reactive electron beam evaporation, Thin Solid Films, 149 291-301, 1987. 

Oekermann, T. Zhang, D. Yoshida, T. Minoura, H., Electron transport and back reaction in nanocrystalline Tio2 films prepared by hydrothermal crystallization. J. Phys. Chem. B 2004, 108, 2227-2235. 

Atomic force microscopy (AFM) is a commonly employed imaging technique for the characterization of the topography of material surfaces. In contrast to other microscopy techniques (e.g., scanning electron microscopy), AFM provides additional quantitative surface depth information and therefore yields a 3D profile of the material surface. AFM is routinely applied for the nanoscale surface characterization of materials and has been previously applied to determine surface heterogeneity of alkylsilane thin films prepared on planar surfaces [74,75,138]. 

Nitrides and Oxynitrides. Crystalline films of NbN and Nb Nj have been prepared. Electron-diffraction studies showed that the former has a NaCl-type structure and the latter is isomorphous with Ti405 and Ta Nj. " The phase 0-TaN, 0 has been prepared by nitriding Ta metal powder with ammonia gas at 850—1200°C. Although it could not be obtained pure, the phase was characterized by X-ray diffraction studies. The free energy of formation of TajNj has been determined as -272 42 kJ mol and that of TaO, 05N0.95 as -396 21 kJ moP. ... 

Cryoelectron microscopy makes it possible to have a direct view into the frozen sample without additional preparation [100]. With the aid of a cryogen (e.g., liquid nitrogen-cooled liquid ethane), the sample is plunge frozen as a very thin aqueous film prepared on a microscopic grid. Subsequently, the vitrified specimen is directly transferred into a precooled electron microscope. Because the specimens are usually ) 2005 by CRC Press LLC... 

The increasing importance of multilevel interconnection systems and surface passivation in integrated circuit fabrication has stimulated interest in polyimide films for application in silicon device processing both as multilevel insulators and overcoat layers. The ability of polyimide films to planarize stepped device geometries, as well as their thermal and chemical inertness have been previously reported, as have various physical and electrical parameters related to circuit stability and reliability in use (1, 3). This paper focuses on three aspects of the electrical conductivity of polyimide (PI) films prepared from Hitachi and DuPont resins, indicating implications of each conductivity component for device reliability. The three forms of polyimide conductivity considered here are bulk electronic ionic, associated with intentional sodium contamination and surface or interface conductance. 

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