Mn implantation was performed with different dosages of 1×1016（1E16）

3×1016（3E16） and 5×1016 cm-2（5E16） into p-Si（100） to prepare Si-based diluted magnetic semiconductor（DMS） samples.Transmission electron microscopy（TEM） and alternating gradient magnetometer（AGM） were utilized to characterize the structural and magnetic properties of both as-implanted samples and samples annealed at 800 ℃ in N2 atmosphere for 5 min.The TEM images of non-annealed samples with fluences of 1×1016 cm-2

3×1016 cm-2 revealed no formation of precipitates.However

for the highest fluence（5×1016 cm-2）

there are nanometer size clusters distributed throughout the implanted region

most of which had the diameters of

5

nm

but several nanoparticles were as big as

1

5 nm.Annealing process partially helped recrystallize the implanted region of 1E16 sample

and was also responsible for the formation of precipitates（with diameters of

1

0 nm）.Analysis of the selected area diffraction pattern determined that the nanometer size precipitates were crystallites with the lattice spacing of 0.333

0.191 and 0.163 nm.These spacings indicate that the most probable phase of the crystallites is MnSi1.7.Before annealing

the saturation magnetization enhanced significantly with the increasing of the Mn fluence.The rising speed of saturation magnetization from 3×1016 cm-2 to 5×1016 cm-2 was less than that from 1×1016 cm-2 to 3×1016 cm-2.In addition

annealing procedure decreased the saturation magnetization of 1E16 sample to nearly zero.These facts indicate that the precipitates did not contribute to the sample magnetism.