Proton and deuteron beams were used to induce nuclear reactions (O-18(p, al
pha)N-15 and O-16(d, p(0))O-17) in order to determine the areal densities o
f O-18 and O-16 in ultrathin films of SiO2 thermally grown on Si in O-18(2)
at low temperatures (700 degreesC and 800 degreesC) and pressures (0.7, 7.
0 and 70.0 mbar). It was observed that film thickness increases with time,
temperature and O-2 pressure. Moreover, O-2 partial pressure was seen to be
determinant in a process that leads to a reversal in the growth kinetics b
ehavior of SiO2 films for the two Si crystalline orientations tested: (0 0
1) and (1 1 1), In the sequence, experimental kinetics were fitted using a
diffusion-reaction model (de Almeida et al,, Phys, Rev. B 61 (2000) 12992).
In some cases good agreement was observed, allowing the determination of d
iffusivities of the oxidizing species through the oxide films. (C) 2001 Els
evier Science B.V. All rights reserved.