• nickel nanotubes;
  • porous silicon;
  • silicon electrochemistry;
  • silicon nanotubes

The present work reports the two types of silicon nanotubes fabrication. The tubular structures based on silicon have been fabricated by immersing mesoporous silicon layer into aqueous electrolyte based on a mixture of NH4F and NiSO4. Similar results are achieved by immersing mesoporous silicon layer that was formed from the silicon wafer previously metallized on its smooth surface with aluminum and after annealing in a N2 environment. In this case, either silicon or nickel nanotubes can easily be formed only by tuning the pH level of the ammonium fluoride solution. The range of the inner diameter of these tubes varies from 40 to 110 nm, whereas the mean value of their tube-wall thicknesses is about 25 nm. The SNT characterization by energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy and their open-circuit potential behaviors show that the silicon tubes have been formed by an etch-stop process where the space-charge region on the silicon side plays a key role for tubes formation. In this paper, the SNT formation mechanism in the aqueous mixture solution of NH4F:NiSO4 using the mesoporous silicon layer as a starting material is discussed. We show that this proposed procedure is new and easy to implement.