Methods for the creation of thin amorphous silicon dioxide (aSiO2) layers on crystalline silicon substrates with very high densities of silicon dangling bonds (so called E' centers) have been explored and volume densities of [E']> 5x10^18 cm-3 throughout a 60nm thick film have been demonstrated by exposure of a thermal oxide layer to a low pressure Argon radio frequency plasma. While the generated high E' center densities can be annealed completely at 300C, they are comparatively stable at room

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... temperature with a half life of about one month. Spin relaxation time measurements of these states between T = 5K and T = 70K show that the phase relaxation time T2 does not strongly depend on temperature and compared to SiO2 films of lower E' density, is significantly shortened. The longitudinal relaxation time T1 ~195(5)us at room temperature is in agreement with low-density SiO2. In contrast, T1 ~625(51)us at T = 5K is much shorter than in films of lower E' density. These results are discussed in the context of E' centers being used as probe spins for spin-selection rules based single spin-readout.