Controlled atmosphere, thin film processing

Temperature uniformity within the reactor is one of the key parameters to be precisely controlled for CVD processes. For thin film deposition on the surface of silicon wafers, multizone (up to five zones) resistively heated furnaces are designed to enable a uniform temperature field for the deposition of the thin film, as shown in Figure 3.21. Several kinds of thermocouples (Types B, K, R and S) are available for CVD systems to measure temperatures. The features of these thermocouples are hsted in Table 3.5. Because the CVD processing atmosphere... 

As described in Section 1.2.3, GIGS can be formed by armeaUng thin films of the metal elements in a chalcogen atmosphere the Showa-SheU-Siemens industrial process is based on this route [80, 81]. Whether a stack of metals or an alloy layer is used depends in part on the annealing process. Single-element depositions are easier to control, but an alloy deposition reduces the number of deposition steps. 

When two or more components are present in a thin film, there is the potential for phase separation and therefore a wide range of microstructural variation. In addition, for solution-processed materials, the solvent acts as a further component that is controllably removed during fabrication. Therefore, in the case of small-mole-cule/polymer systems, there can be several factors that determine the overall phase behavior first, the thermodynamics of mixing between components and the balance of entropic and enthalpic contributions to the free energy of mixing, AG ixi second, the interaction between solution and substrate or atmosphere interfaces and finally, the kinetics of solvent evaporation and changes to the solution that this induces, such as viscosity variation or phase separation within the solution. It should be noted that these processes are often far from thermodynamic equilibrium leading to a film microstructure that can sometimes be difficult to predict. 

Although the ASTM D 814 has been generally used as a method for rubber testing recently, the classical method of measuring water vapour has been still used the gravimetric or dish method. Such a method is detailed in ISO 2528 and similarly in ISO 6179 which can be applied to any sheet material with flat, thin and can be processed to form a vapour resistant barrier such as plastic films, fabrics coated with rubber or plastics. The procedure deals with the dishes containing a desiccant and closed by the material to be tested are placed in a controlled atmosphere. The dishes are weighed at suitable interval of time... 

Examples of dense silica, hybrid silica, metal oxides, solid-state metal oxide solutions, or colloidal self-assembly are unlimited. However, the recent developments to accurately control processing conditions (e.g., atmosphere, temperature, and motion) led to films with unique properties (see Figure 9.6) [52,53]. These progresses concern mesoporous coatings with controlled pore size and structure [26], hard template infiltration and/or replication [54-58], nanostructured epitaxial low-quartz thin films [59], ultrathin nanostructured supported networks [60,61], ultrathick porous Ti02 layer prepared from aqueous solutions [51], coatings with hierarchical porosity [62], multilayer porous stacks [63], colloidal MOF layers [64,65], pillar planar nanochannels (PPNs) for nanofluidics [66], and so on. 

Speleothem precipitation rates from thin water films open to the cave atmosphere are controlled by three processes (Baker and Smart, 1995 Baker et al., 1998) 1) chemical reactions at the calcite-solution interface as described by the rate equations of Plummer et al. (1978) through which precipitation rates can be calculated when the concentrations of reactants are known 2) mass transport of reactants through the solution towards or away from the speleothem surface and 3) the rate-limiting reaction H" + HCO = H2O + CO2, through which CO2 is released into the cave atmosphere. Buhmann and Dreybrodt (1985a,b) have solved the transport equations taking into consideration these three mechanisms in order to obtain precipitation rates. For speleothems, Eq.3 can approximate these processes within 10% ... 

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