Vibration modes of oxygen dimers in germanium

Absorption in the infrared region of the spectrum was studied for both the as-grown Ge crystals and the Ge crystals irradiated with fast electrons (with subsequent heat treatment); the crystals were preliminarily enriched with 16O or 18O isotopes. The vibrational absorption bands observed in Ge and peaked at 780, 818, and 857 cm-1 are attributed to complexes composed of two atoms (dimers) of 16O, whereas the bands at 741, 776, and 811 cm-1 are attributed to complexes of 18O atoms. It is established that electron irradiation of Ge crystals at temperatures near 295 K with subsequent heat treatment at 120-250 deg. C brings about an increase in the intensities of bands peaked at 780 and 818 cm-1. The band peaked at 857 cm-1 does not change its intensity under irradiation and, by analogy with Si, is identified with another configuration of oxygen dimers in Ge. The bonding energy of dimers responsible for the bands peaked at 780 and 818 cm-1 is estimated at 0.35-0.4 eV