Solid state studies : transition ions in zinc oxide

Furnace control facilities have been developed and crystals of ZnO with Mn, Co, Ni and Cu as impurities grown from a PbF2 flux. Visible spectra of Ni- and Co- ZnO in a variety of concentrations have been taken at temperatures from 1°K to 300°K. Sharp lines have been studied using high resolution to avoid slit effects. Temperature, polarisation and concentration dependence have been analysed to determine the nature of the transitions involved. Trigonal crystal field calculations have been performed to fit the observed electronic levels. Evidence has been found for the assignment of the visible band of Ni - ZnO to two electronic transitions and their phonon sidebands. An extra level, which may be due to some form of Jahn-Teller interaction, has been observed. Several parts of the spectrum show characteristics of a reduction of off-diagonal matrix elements by vibronic coupling. Lines due to pair interactions have been identified on the low energy side of the visible bands in Ni- and Co - ZnO. For Ni - ZnO the interaction cannot be due to spin, which is quenched in the ground state