Functional layer

Because of their conductivity, reflecting effect, and light barrier properties, metallized films are increasingly used as functional coatings in technical applications. Examples include battery cell cases, prepaid telephone cards, self-adhesive labels, insulation foil in the building industry, decorative foil for design elements, security features for bank notes, and tear tapes, etc. 

In the electronics sector, metallized films and nonwovens are used as EMI 

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Etching. After a resist is patterned on a wafer, the exposed or unwanted substrate is removed by etching processes. Subsequentiy the resist is removed, leaving a desired pattern in a functional layer of the integrated circuit. Etching is performed to pattern a number of materials in the IC fabrication process, including blanket polysiHcon, metal layers, and oxide and nitride layers. The etch process for each material is different, and adapted to the material requirements of the substrate. 

In practice, surface modifications are restricted to sensors of the ATR- or FEWS-type. For other transducer layouts, the sample - radiation interaction is less localised, making a modification difficult to impossible. Depending on the analytes and the environment of the sensor, two basic surface modification strategies can be used to enhance the function of vibrational spectroscopic optical chemical sensors. The functional layers can either be... 

FIGURE 1.12 Cross-sectional image of a five-layer cell with the anodic substrate Ni-YSZ, anodic functional layer Ni-ScSZ, electrolyte ScSZ, and interlayer GDC prepared with a tapecasting technique [79]. 

SOFC electrodes are commonly produced in two layers an anode or cathode functional layer (AFL or CFL), and a current collector layer that can also serve as a mechanical or structural support layer or gas diffusion layer. The support layer is often an anode composite plate for planar SOFCs and a cathode composite tube for tubular SOFCs. Typically the functional layers are produced with a higher surface area and finer microstructure to maximize the electrochemical activity of the layer nearest the electrolyte where the reaction takes place. A coarser structure is generally used near the electrode surface in contact with the current collector or interconnect to allow more rapid diffusion of reactant gases to, and product gases from, the reaction sites. A typical microstructure of an SOFC cross-section showing both an anode support layer and an AFL is shown in Figure 6.4 [24],... 

The introduction of such a layer can dramatically improve the fuel cell performance. For example, in the SOFC with bilayered anode shown in Figure 6.4, the area-specific polarization resistance for a full cell was reduced to 0.48 Hem2 at 800°C from a value of 1.07 Qcm2 with no anode functional layer [24], Use of an immiscible metal oxide phase (Sn()2) as a sacrificial pore former phase has also been demonstrated as a method to introduce different amounts of porosity in a bilayered anode support, and high electrochemical performance was reported for a cell produced from that anode support (0.54 W/cm2 at 650°C) [25], Use of a separate CFL and current collector layer to improve cathode performance has also been frequently reported (see for example reference [23]). 

FIG U RE 6.4 SEM cross-sectional micrograph of an SOFC, showing an anode support layer, anode functional layer, electrolyte, and cathode [24]. Reprinted from [24] with permission from Elsevier. 

In addition to bilayered electrodes with a functional layer and a support layer, electrodes have also been produced with multilayered or graded structures in which the composition, microstructure, or both are varied either continuously or in a series of steps across the electrode thickness to improve the cell performance compared to that of a single- or bilayered electrode. For example, triple-layer electrodes commonly utilize a functional layer with high surface area and small particle size, a second functional layer (e.g., reference [26]) or diffusion layer with high porosity and coarse structure, and a current collector layer with coarse porosity and only the electronically conductive phase (e.g., reference [27]) to improve the contact with the interconnect. 

In addition to bilayered anode and cathode functional layer and current collector/sup-port layer combinations, bilayered electrolyte structures are commonly fabricated, particularly for low-temperature operation below 700°C, by a variety of processing methods. Bilayered electrolytes are used for several purposes ... 

Usually, SOFC electrodes are composed of two (or sometimes more) layers, where the first (the porous anode in Figure 3.3) has mainly a structural function, and the second is a functional layer (called the reaction zone in Figure 3.3), with the main aim of promoting the electrochemical reaction. 

Noteworthy and important for sensing purposes is the response of the TRITC-functionalized layers T1-T3. The fluorescence response of these layers increased between 24 and 87% in the presence of HS04 , while the same layers showed a fluorescence intensity decrease in the presence of PhPCV between 35 and 56%. 

Ceramic foils are produced continuously by tape-casting methods. These ceramic tapes consist of an organic binder and oxide powder material, for example, zirconia, titania or alumina. If it is possible to integrate the production process of a micro structured reactor into such a continuous process, production costs would decrease strongly. An early approach used unstructured ceramic foils to build up a micro reactor [159], The reactor consisted essentially of two functional layers, a reaction layer and a heating layer (Figure 4.102). 

Different laminated structures are constructed by arranging the functional layers according to the requirements of the chemical or biochemical assay. Commercially available assays include those for creatinine, albumin, amylase, bilirubin, cholesterol, triglycerides, and certain alkali and alkaline earth metals. 

Figure2.20 Examples of microreactors (150 mm x 150 mm), with two functional layers. Outside tempering. Inside preliminary heating, mixing, dwell channel (volumes approximately 3 ml), with friendly permission of the Little Things Factory GmbH, llmenau, Germany.

In an SOFC, the electrochemical reactions take place in the electrodes in the functional layer, that is, a zone within a distance of less than 10-20 pm from the electrolyte surface [5,136-138], The portion of the electrode beyond this width is principally a current collector structure, which has to be porous to permit the admission of gas to the functional layer where the oxidation and reduction reactions occur. Besides, the electrolyte has to be gas impermeable to avoid direct combination and combustion of the gases [137], The essential parts of the SOFC, that is, the electrolyte, the anode, and the cathode, are made of ceramic materials produced with appropriate electrical conducting properties, chemical and structural stabilities, similar expansion coefficients, and negligible reactivity properties [135],... 

The microelectronics industry is continuously reducing the feature size of integrated circuits. In 2006, a DRAM halfpitch, i.e. line widths of 70 nm will be put into practice, until 2010 a reduction to 45 nm is laid down in the International Technology Roadmap for Semiconductors [1]. An integrated circuit consists of a series of patterned functional layers (insulators, metal wires). The structure of each layer is transferred from a mask via a photolithographic process followed by etching or ion implantation. These manufacturing processes must be able to produce the required feature sizes. 

In the photolithographic process, the functional layer is covered by a photoresist film. State-of-the-art circuits are fabricated with chemically amplified photoresists consisting of a polymer with an acid-labile pendant protection group, photoacid generator molecules (PAG), and additional additives [2], Upon exposure to UV radiation through a patterned mask, the PAG is decomposed generating a low concentration of acid. In a post-exposure bake... 

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