Parallel stripes of nanostructures on an n-type Si substrate were fabricated by implanting 30keV Ga+ ions from a focused ion beam source at three different fluences: 1 x 1015, 2 x 1015 and 5 x 1015 ions/cm2. Two sets of implantations were carried out. In one case, during implantation the substrate was held at room temperature and in the other case at 400C. Photo-emission electron microscopy measurements were carried out on these samples. The implanted parallel stripes, each with a nominal dimension of 4000 x 100nm2, appeared as bright regions in the photo-emission electron microscopy image. Line scans of the intensities from photo-emission electron microscopy images were recorded along and across these stripes. Intensity profile at the edges of a line scan was broader for the implantation carried out at 400C compared to room temperature. From the analysis of this intensity profile lateral diffusion coefficient of Ga in silicon was estimated assuming that the photo-emission electron microscopy intensity was proportional to Ga concentration. The diffusion coefficient at 400C was estimated to be about 10−15m2/s. No significant dependence of diffusion coefficient on ion fluence was observed in the fluence range investigated here. Radiation-enhanced diffusion was considered in the light of the associated defect distribution due to lateral straggling of the implanted ions.

Lateral Straggling and its Influence on Lateral Diffusion in Implantation with a Focused Ion Beam. R.Batabyal, J.C.Mahato, A.Roy, S.Roy, L.Bischoff, B.N.Dev: Nuclear Instruments and Methods in Physics Research B, 2011, 269[9], 856-60