Measurement of low energy ion implantation profiling in seeds by the PIXE and SEM with slicing up technique

The mutation effect caused by low energy ion beam implantation into dry seeds has been accepted and turned into practical application. But its mechanism is still not clearly understood. According to the energetic ion range theory, ions with hundreds of keV energy can not directly affect the nuclei of the cell inside the embryo part of the seeds underneath the thick seed coat. It is obviously important to measure the concentration-depth distribution of the implanted ions in seeds for study of the mechanism. 200 keV V+ ions were implanted into dry seeds of peanut with a dose of 9 x 1016 ions/cm2, then the seeds were sliced up into 15 μm thickness along the incident beam direction. The concentration of the V in each slice was measured with PIXE (Particle Induced X-ray Emission). It is shown that the concentrations of the V in un-implanted peanut are lower than the detection limit of PIXE. But the concentrations in the slices of implanted peanut up to 121-135 μm depth are higher than the PIXE detection limit. More than 98% of V are in the first slice (corresponding to 0-15 μm depth), however, the rest part of V distribute over a wide depth range. This fact indicates that the structure in peanut seeds is not homogeneous, the implanted ions can reach a much deeper depth than that predicted by the range theory