A simple energy spike model is used to interpret the experimental results of medium-range order in ion-implanted amorphous silicon. This model can justify the liquid state, which is speculated to be the initial state of paracrystalline silicon in ion implantation. According to this model, we hypothesize that a crystallite is produced from the hottest spot of a liquid state. As solidification to an amorphous state proceeds from the boundary, the central spot undergoes the maximum undercooling. Such a condition can induce homogeneous crystallization, but it is not possible to form a perfect crystal therein. One can envisage that the spike finally becomes a paracrystallite. In support of the theory, we provide the key equations of the model in this article. But this model still needs to be verified by computer simulations in the future. (C) 2004 American Vacuum Society.