Disclosed are methods for fabricating pyrolysed carbon nanostructures. An example method includes providing a substrate, depositing a polymeric material, subjecting the polymeric material to a plasma etching process to form polymeric nanostructures, and pyrolysing the polymeric nanostructures to form carbon nanostructures. The polymeric material comprises either compounds with different plasma etch rates or compounds that can mask a plasma etching process. The plasma etching process may be an oxygen plasma etching process.