Fabrication of densely distributed Si nanorods by Ar⁺-ion bombardment

For the direct fabrication of densely distributed one dimensional nanostructures on Si substrates, Si (1 0 0) surfaces were bombarded by obliquely incident 3 keV Ar⁺ ions with a simultaneous supply of Mo seed atoms at various temperatures ranging from room temperature to 400 °C. The surface sputtered at room-temperature with Mo seeding was characterized by the nanocones pointing in the direction of the incident ion beam. In addition, they possessed a so-called "web" at their acute-angle side. This web decreased in size with an increase in the sputtering temperature. Thus, the projections fabricated at elevated temperatures were featured by the nanorod-like structure rather than conical structure. With increasing the sputtering temperature, projections decreased in base diameter (from ∼90 nm at 200 °C to ∼50 nm at 400 °C) while they increased in both length (from ∼160 nm at 200 °C to ∼240 nm at 400 °C) and numerical density (from ∼5 × 10⁷ mm^-2 at 200 °C to ∼1.2 × 10⁸ mm^-2 at 400 °C). The controlled fabrication of such densely distributed one dimensional nanoprojections on Si using ion beam technique, we believe, would open up a variety of applications such as nanoelectronics and optoelectronics devices.