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How pure could germanium become through zone refining in the early 1950s?
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zone melting
Figure 1: Schematic representation of (A) normal freezing, (B) zone refining
Through the process of zone refiningβa technique first described by the U.S. scientist W.G. Pfann and implemented in the early 1950sβgermanium reached levels of purity that were previously unheard of. Specifically, the material could be refined to contain less than one part of detectable impurity in 10,000,000,000 parts of germanium.1
This extreme level of purification was essential for the manufacture of transistors, as the electrical properties of semiconductors are highly sensitive to even the slightest trace of contaminants.12