A method to grow arrays of multibranched carbon nanostructures is explained. We use the electron-beam-induced deposition method using a transmission electron microscope with ∼10−6 Torr vacuum where hydrocarbons are present in the chamber. Saw-tooth nano-patterns were made with a focused ion beam in porous silicon substrates. Due to the dielectric properties of the films the patterns provide the corresponding sites in which high local electric fields appear during irradiation thus allowing the hydrocarbons to become preferentially attracted to those active sites. We found that the adequate ion dose to create well defined saw-tooth nano-patterns was between 8 and 10 nC/μ2 at 30 kv. Electron energy-loss spectroscopy on the branched carbon nanostructures show a high concentration of sp2 sites suggesting that they are made of graphite-like amorphous carbon.