Optimised process for fabricating functional silicon nanowhisker arrays

Silicon nanostructures, called silicon nanowhiskers, are grown by electron beam annealing of wafer silicon. It is desirable to be able to control sizes and locations of arrays of silicon nanowhiskers for field emission applications. Nitrogen, oxygen and silicon ions were implanted at 15-24 keV with fluences ranging from 1012 to 1015 ions cm−2 to investigate the possibility of suppressing the silicon nanowhisker growth in specified regions and to search for the minimum level of implanted ions necessary to suppress silicon nanowhisker growth. Particularly interesting results were obtained for the nitrogen ion implantation series where total suppression is achieved by implanting 5 × 1014 N+ cm−2. However, implanting 1 × 1014 N+ cm−2 results in an increase in nanowhisker density of a factor of three coupled with a decrease in nanowhisker height by a factor of two. Silicon was also found to suppress silicon nanowhisker growth successfully; however oxygen implantations resulted in a decrease of nanowhisker growth with increasing fluence but suppression of nanowhisker growth at 1 × 1015 O+ cm−2 was not achieved. Selected results are presented showing the possibility of controlling the silicon nanowhisker growth area by low-energy nitrogen and silicon ion implantation.