Divacancy control of the balance between ion beam induced epitaxial crystallization and amorphization in silicon.

Amorphous layers in silicon can be epitaxially regrown in the solid phase at temperatures as low as 150C under ion irradiation. However, at high ion dose rates and/or lower temperatures the process is reversed resulting in planar, layer by layer, amorphization. The transition between the two regimes has been investigated as a function of temperature, ion species and ion dose rate. The dynamical equilibrium condition for this reversal in terms of dose rate and temperature is characterized by an activation energy of ~1.2eV. For different ions, the same transition condition is valid if scaling is performed with the square of the number of displacements produced by each ion. The activation energy and the second order dependence on defect production by individual ions suggest that divacancies produced within individual cascades control the dynamical equilibrium.