Substrate is mounted

Low contamination levels are readily achieved in laboratory scale UHV systems. Very high costs inhibit the use of UHV in industrial scale systems, however, so another, local-UHV approach has been proposed, viz. the plasma box reactor [152]. The substrate is mounted in a box, which is surrounded by a shell, which is pumped to a low pressure. The process pressure in the box is maintained by a throttle valve. As the pressure in the box is larger than the pressure in the surrounding shell, contaminants diffuse outwards and the incorporation of contaminants in the deposited layer is low. 

The substrate is mounted about 25 mm. away from the vapor source in a copper frame which holds it in place, backed by an externally heated copper block. In this manner the lower face of the substrate is exposed to the vapor beam and maintained at the desired temperature by heating it at its upper face. The temperature is regulated within about 1 % by a proportionating potentiometer controller. The substrate consists of a square plate of an ionic salt with sides approximately 5 mm. long and 1 mm. thick. A freshly cleaved face of the salt crystal is exposed just prior to a run. A thermocouple in contact with the lower face of the support indicates the film temperature. 

The substrate is mounted on a graphite susceptor (usually SiC-coated) and a radio frequency (rf) field is used to inductively heat the susceptor. 

The design of sandwich cells (FIGURE 3) is defined, firstly, by the direction of mass transfer. In the upper part of the crucible the material transport occurs upwards and the substrate is mounted on a graphite or tantalum holder. Polycrystalline SiC powder is the most... 

The most commonly used method to measure the concentrations of corrosive gases in field environments is to adsorb the gases on chemicaUy treated filter paper, sometimes followed by a water extraction or chemical treatment, and then to determine the composition and quantity spectroscopically. IBM [75] developed a stacked canister sampler that was adapted for use in the BatteUe studies [79]. Each element in the canister stack collects a specific poUutant. The canisters are easily deployed anywhere in the world, the only inconvenience being that an air pump is required to draw a well-controlled air volume. The reliability of these pumps, based on the author s experience, is less than desirable but adequate. A similar technique, developed largely under the sponsorship of the U.S. EPA, is the "denuder tube. This method is also based on species-specific absorption of pollutants on a chemically treated surface, but in this case a permanent honeycomb substrate is mounted inside a tube. For field sampling, the tubes are stacked, the number depending on the number of species to be analyzed. Airflow pumps are also required in this approach. While this method is more cumbersome than the IBM/Battelle canisters, all the equipment and follow-up chemical analysis can be obtained commercially. 

The apparatus consists of a tip-position controller, an electrochemical cell with tip, substrate, counter and reference electrodes, a bipotentiostat and a data-acquisition system. The microelectrode tip is held on a piezoelectric pusher, which is mounted on an inchwomi-translator-driven x-y-z tliree-axis stage. This assembly enables the positioning of the tip electrode above the substrate by movement of the inchwomi translator or by application of a high voltage to the pusher via an amplifier. The substrate is attached to the bottom of the electrochemical cell, which is mounted on a vibration-free table [, and ]. A number... 

A substrate is a robust element that provides mechanical support for the die. It can be mounted with more than one die such packages are called multichip modules. Because parasitic capacitance effects are directiy proportional to the dielectric constant, substrate material should have a low dielectric constant. 

Pig. 2. (a) The cell mount design of the integrated PV array of Pigure 1, which uses laminated conductive and insulating layers on top of an aluminium substrate in a printed circuit board-type panel (7). The array produces 20 kW at 20°C ambient and 850 W/m direct sunlight, and measures 155 m. The lens is a molded acryUc Presnel lens parquet mounted on the front of the array stmcture. The PV panel is mounted on the back of the array stmcture and is... 

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

A hot solution (0.1—1 %) is added drop-wise onto a pre-heated substrate such as a glass slide or a piece of mica sheet (the substrate may have been coated with vapor-deposited C). After being dried and solidified, the resulting thin film specimen is mounted onto a specimen grid with the aid of water surface if the specimen is insoluble in water. When a glass slide is used as a substrate, a dilute aqueous solution (<0.02M) of hydrofluoric acid (HF) might be used for easy detachment. The resulting thin film can be... 

Enzymes are known for their exquisite shape selectivity and regio- and stereoselectivity with respect to their substrates [16,17], For example, different versions of the cytochrome P-450 enzyme family catalyze the hydroxylation of substrates as diverse as P-naphthylamine and vitamin D [18,19], The specificity of the P-450 enzymes derives from the shape of the substrate-binding cavity, which is contiguous with the active site. (Unfortunately, in heterogeneous catalysis, substrate is often the term used to describe the stratum or support upon which the catalyst is mounted. The analog of the enzymatic substrate in heterogeneous catalysis is called the feed or reactant.)... 

The low pressure air abrasion which was used to separate rows of detector elements turned out to be difficult to control and devices were frequently damaged during the process. To overcome this, the epoxy layer 34 is applied but prior to curing the same the detector wafer 40 is mounted onto the substrate 10. Pressure is applied and the assembly is heated. Substantially all of the adhesive layer that was previously formed between the wafer and contact pads 38 is eliminated. 

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