Tungsten evaporation

Fig. 20. Reaction tube for semi-conductivity measurements on thin films. A, Pt conductance leads and Pt/Pt-Rh thermocouples B, tungsten tensioning spring C, four Pt foil conductance electrodes fused onto the inner wall D, plated tungsten evaporation filament. From ref. 150.

FIGURE 7.13. Tungsten evaporation coils for thin-film technology. By courtesy of Plansee AG, Austria. 

TABLE 7.2. Chemical Compounds which can be Evaporated with Tungsten Evaporation Sources"... 

Logan and Kemball ( 5) also studied the decomposition of ammonia on a tungsten evaporated film and observed nitriding to various extent. 

Tantalum is a gray, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum. Tantalum is almost completely immune to chemical attack at temperatures below ISOoC, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide. Alkalis attack it only slowly. At high temperatures, tantalum becomes much more reactive. The element has a melting point exceeded only by tungsten and rhenium. Tantalum is used to make a variety... 

Tungsten oxytetrachlofide [13520-78-0], WOCl, mp 211°C, bp 221°(Z, is a red crystalline soHd. It is soluble in carbon disulfide and ben2ene and is decomposed to tungstic acid by water. It may be prepared by refluxing sulfurous oxychloride, SOCI2, on tungsten trioxide (12) and purified after evaporation by sublimation. 

Other uses are in thin film technology where coatings are applied by vacuum deposition. Tungsten boats, or coils fabricated from wire are heated by direct resistance heating and used to evaporate Ag, Al, Au, B, Ba, Ce, Cr, Fe, In, Mg, Mn, Ni, Pa, Pt, SiO, Te, V, Zn and Zr. 

Procedure (tungsten in steel). Dissolve 0.5 g of the steel, accurately weighed, in 30 mL of the mixed acid by heating, oxidise with concentrated nitric acid, and evaporate to fuming. Extract with 100 mL water, boil, transfer to a 500 mL... 

The following experimental details apply both to the determination of tungsten with bromine as internal standard, and to the experiments of Table 7-2. The solutions filled a 3-ml container made by sectioning a 10-ml beaker. To prevent" evaporation and to maintain a fixed distance between x-ray tube window and sample surface, the beaker-section was covered with Mylar film, 0.0025 cm thick, placed in a plastic sample holder and pressed firmly against the sample drawer. The Mylar film attenuated the x-rays uniformly enough so as not to affect the precision of the results. 

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