Influence of silicon dioxide doping on morphology of silicon nanowires grown by floating zone method

On the surface of silicon sticks with one end melted, which were doped with different mass percentages of silicon dioxide (x = 0, 0.5%, 2%, 6% and 10%), silicon nanowires with different morphologies were synthesized by the floating-zone (FZ) melting method. The change of morphology was studied by scanning electron microscopy (SEM) and field emission SEM (FESEM). All the nanowires have a uniform diameter of about 20 nm when x less than or equal to 0.5%, but when x greater than or equal to 2%, there coexist several nanowires that have different diameters ranging from 20 nm to 500 nm. As x increases to 10%, thick nanowires of about 400 nm diameter become dominant and the thin ones become deteriorated. A model for the growth mechanism was assumed based on the morphology change of the nanowire.