An optical absorption band at 9jx has been correlated with the oxygen content in silicon. Pulled silicon crystals were found to contain up to 10 18 oxygen atoms per cm 3 which seem to originate from the quartz crucible. The oxygen concentration in silicon crystals prepared by the floating zone technique in vacuum was found to be less than 10 16 oxygen atoms per cm 3 . The 9/x absorption due to silicon-oxygen bond stretching vibrations provides a possibility for a quantitative oxygen analysis of high sensitivity. A corresponding absorption in germanium at 11.6/z is believed to be due to a germanium-oxygen vibration. KAISER,KECK, AND LANGE crystals pulled from a quartz container. Optical absorption measurements at 9JJL are suitable for a quantitative oxygen analysis in silicon. Oxygen-free silicon has a weak lattice absorption at 9/x. A corresponding absorption at 11.6/x in germanium, due to Ge-0 stretching oscillations, was found to be superimposed above a weak lattice band.

The oxygen content of pulled silicon crystals, determined by vacuum fusion gas analysis, is correlated with the infrared absorption at 9 μ. In vacuum and in helium or hydrogen of 1 atmos, the oxygen concentration of a liquid zone of silicon (about 20 mm2 in cross section) can be rapidly decreased. In an oxygen atmosphere or in contact with quartz, liquid silicon picks up oxygen quite readily. A maximum oxygen content of 2×1018 oxygen atoms per cm3 was observed. Silicon single crystals pulled from a quartz crucible exhibit fluctuations in oxygen concentration both perpendicular and parallel to the pulling direction. Explanations of these effects are offered and the influence of various pulling parameters is discussed.

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