HYDROGEN PASSIVATION OF THE PARAMAGNETIC CENTERS IN AMORPHOUS REGIONS OF ION-IMPLANTED DIAMOND

The effect of hydrogenation (j = 30-mu-A/cm2, E = 300 eV, T = 200-degrees-C) on the paramagnetic centers (PC) in amorphous regions (AR) of phosphorus implanted (100 keV, 1.8 x 10(15) cm-2) diamond is studied. The passivation of the vacancy type defects by hydrogen atoms have been analyzed in terms of the MO LCAO (CNDO/2) method on a cluster approach based on the example of vacancy and divacancy models. The calculations show that the saturation of all dangling bonds with hydrogen atoms causes the total removal of the local levels from the band gap for the vacancy case and almost the total removal for the divacancy case. The MO LCAO (CNDO/2) calculation of the interaction of hydrogen atoms with the intrinsic atoms in tetrahedral (T) interstitial sites modifies the structure of their electronic levels but passivation of these defects does not take place. The calculations predict that the T-interstitialcy can reveal donor properties. The activation energy of the defect level near the c-band reduces as a result of the interaction of this defect with hydrogen atoms. The experimental and theoretical results are in good agreement with a model of the isotropic EPR signal formation in amorphous diamond. The main idea of this model is that the exchange interaction between point paramagnetic defects and/or motion of spin carriers simultaneously with the disordering of crystal structure results in a transformation of multicomponent anisotropic spectra of these defects to one isotropic line. The contribution of vacancy-type defects to the formation mechanism proposed predominates.