Raman scattering application was introduced to directly probe the depth profile of structural changes in a very thin surface layer of F+-implanted Si by use of a single Ar+ laser (488 nm) excitation. The results of Raman scattering and sheet resistance measurement showed an unusual annealing behavior of the F+-implanted Si:In the range of annealing temperature T-a from 200 degrees C to 400 degrees C, disordering was observed to increase with increasing T-a but a stronger trend of ordering with T-a increasing further above 400 degrees C. This abnormal behavior could be explained as due to competition between the ordering effect of thermal annealing with increasing T-a and the disordering effect of the implanted fluorine ions randomly breaking the Si-Si crystal bonds in the surface diffusion layer. (C) 1996 American Institute of Physics.