Boron doped superlattices have been used to detect the diffusion of self‐interstitials in Si. Interstitials were generated in the near‐surface region by 40 keV Si implantation followed by diffusion at 670–790 °C. The interstitial diffusion profile at 670 °C is stationary fort≤1 h, demonstrating that the penetration depth of interstitials is limited by trapping. The concentration of traps is estimated to be ∼1017/cm3. For sufficiently long annealing times, interstitials diffuse beyond the trapping length with an effective trap‐limited diffusivity ranging from ∼6×10−15cm2/s at 670 °C to ∼1×10−12cm2/s at 790 °C. The high interstitial supersaturation adjacent to the implant damage drives substitutional B into metastable clusters at concentrations below the B solid solubility limit. ©1995 American Institute of Physics.