Si dangling bond interface defects (Pb0,Pb1) were probed by electron spin resonance in entities of (100)Si with ultrathin SiO2 grown in ozonated de-ionized water solution at room temperature. After photodesorption of passivating hydrogen, Pb0 appears with densities up to ∼5×1012 cm-2, a value five times larger than the one standardly attained with high temperature thermal growth. Thus standard quality thermal Si/SiO2 interface properties, as exposed by the Pb0-type defects criterion (interface traps), are not obtained by oxidation in ozonated water solutions at room temperature. The interface quality may be upgraded by providing additional thermal budget. Yet standard qualitity is still not attained after vacuum annealing at 600 °C. © 2003 American Institute of Physics.