Raman spectroscopy of hydrogen molecules in germanium

Single-crystalline germanium samples exposed to hydrogen and/or deuterium plasma are studied by Raman scattering. Two bands at 1980 and 4155cm-1 are assigned to local vibrational modes of Ge–H and H2H2, respectively. Polarization sensitive Raman scattering spectra suggest that the plasma treatment results in {111} platelets whose basic units are Ge–H bonds. The signal at 4155cm-1 is shown to result from molecular hydrogen trapped within these platelets. Another broad Raman signal around 3930cm-1 seems to be due to H2H2 trapped in some other type of voids formed during the plasma treatment. Two sharp peaks at 3826 and 3834cm-1 are assigned to ortho- and para-H2H2 trapped at the interstitial T site.