Miller process the gold is removed and processed in the manner required for sale or use. The resulting gold is 99.95% pure, but of lower purity than gold produced by the other common refining method, the Wohlwill process, which produces gold to 99.999% purity. The Wohlwill process is commonly used for producing high-purity gold, such as in electronics work and the manufacture of some silicates, where exacting standards of purity are required. When highest purity gold is not required, refiners often utilize the Miller process due to its relative ease, quicker turnaround times, and because it does not tie up the large
Ultra-high-purity steam for oxidation and annealing and is both less expensive and safer. An effective passivation of the rear surface of industrial solar cells is a prerequisite to considerably improve the conversion efficiency. An excellent level of surface passivation on lowly doped p-type surfaces is provided by thermal grown silicon oxides. However, dry thermal oxidation processes require relatively high temperatures (>1000 °C) and, due to the low growth rate, long process times. To decrease both oxidation temperature and process time the dry oxidation process can be replaced by a wet oxidation followed by nitrogen annealing. Best cell performance requires a forming gas anneal after firing. Ultra-high-purity