Electron spin resonance investigation on the low temperature Si-O bonding

The Si-O bonding has been investigated in two systems: O/sup +/ implanted silicon and on hydrogenated porous Si surface exposed to air. The oxidation in both cases is accompanied by the formation of P/sub b/ like centers. The paramagnetic defects are generated during the formation of the oxide network. EPR (electron paramagnetic resonance) has been used to determine the defect population evolution in both systems. The samples are annealed in an isochronal multistep procedure for temperatures in the range 50-800/spl deg/C. A common feature has been found for P/sub b/ centers behaviour in bulk and on the surface in respect with both type of samples used. A dramatic effect of surface reconstruction in the early stage of porous silicon oxidation at about 350/spl deg/C has been determined. At this temperature the P/sub b/ concentration reaches its maximum. The O/sup +/ implanted samples show the same feature but with a weak and broader peak of P/sub b/ concentration than in the case of PS (porous silicon). The maximum appears at 300-400/spl deg/C. We have found that the annealing behaviour of oxygen related defect concentration has a strong dependence on the thermal history for both systems.