Visible and VUV optical absorption studies of Mg-colloids and colour centres in MgF_2 crystals implanted by 100 keV Mg-ions

摘要

100 keV Mg ions have been implanted into MgF_2 crystals with a fluence of 10~(17) ions/cm~2 at liquid nitrogen temperature. After warming to room temperature optical absorption measurements over the range 2.0-11.5 eV revealed F-type centres in the visible spectral region and bands at 7.8 eV and near 6.5 eV in the vacuum ultraviolet region. Analysis of defect annealing at elevated temperatures showed a mutual decay of the latter bands with the F-type centres and thereby their association with complementary fluorine interstitial defects. The growth and decay of a Mg colloid band near 4.43 eV was studied. At the highest annealing temperatures an XPS analysis shows that oxygen diffuses into the crystal forming MgO near the implanted surface, thus substantially modifying the optical absorption spectrum.