Figure 1
Schematics of the different steps involved in the site-selective growth of WOx nanowires using the local stress induced by implanted ions.
(a) A WOx thin film is deposited on a (100) Si substrate by electron-beam evaporation. (b–d) Processing using a focused ion beam; (b) Ga ions are implanted in nanoscale areas; (c) the sample is annealed at 600 °C; (d) a small number of WOx nanowires grow in the Ga-ion-implanted nanoscale region. The magnified schematic depictions of the regions highlighted in (c,d) show the nanoscale morphology of the WOx thin films and nanowires in the ion-implanted (dark blue) regions where the grains are smaller. (e–g) Processing using an ion implanter; (e) As, Ar, or N2 dopants are selectively implanted through a shadow mask onto the WOx thin film; (f) compressive stress arises from the difference between the thermal expansion coefficients of the thin film and the substrate during annealing at 600 °C in a furnace as in (c,g) WOx nanowires grow only in the ion-implanted region because the ions increase the compressive stress locally. (h1-3) Cross-sectional diagram of growth mechanism using compressive stress induced from the difference in TECs and ion implantation. Large red arrows indicate the compressive stress from difference in TECs; small red arrows indicate the additional compressive stress from ion implantation in the desired area. (h1-3) Cross-sectional diagram showing the growth of nanowires due to compressive stress. Large red arrows indicate the compressive stress from difference in TECs; small red arrows indicate the additional compressive stress from ion implantation in the desired area.
