ABSTRACT
In contrast to silicon, indium is rare in the earth’s crust and only appears in concentrations up to about 100 parts per million in zinc ores. Zinc mining is the main source of globally produced primary indium. Since the mid-1980s the importance of indium is increasing. Due to its particular characteristics, that is, semiconducting and simultaneously applicable as transparent layers, it is used as indium tin oxide (ITO) in liquid crystal displays (LCDs) and touch screens. Moreover, indium is used in PV such as copper indium gallium selenide (CIGS) cells. According to the US Geological Survey 795 tons of indium were produced in 2012, 55%–85% of which were processed to ITO and further to thin ITO films by vacuum evaporation (see also Section 12.1.1.4).
