Investigation of conducting nanostructures on ta-C films made by FIB lithography
Tetrahedral amorphous carbon (ta-C) films with high sp3 content produced by mass filtered vacuum arc deposition were modified by Ga+ FIB irradiation.
Surface swelling occurs as a function of fluence, caused by ion induced conversion of sp3 to sp2 hybridized carbon atoms. A model for diamond swelling was applied to ta-C films to estimate the swelling for fluences up to 1 x 1016 cm-2. For higher fluences data from TRIDYN simulations were included due to sputtering in a good agreement with the experiments.
Van der Pauw structures were produced by means of Ga+ FIB lithography. A decrease of the sheet resistance with increasing fluences due to the evolution of graphitic regions was observed. The lowest value of 290 Ω/ was achieved at 1.6 x 1017 cm-2.
Additionally, conducting graphitic wires were produced (length: 10 µm, width: 300 nm to 5 µm). The wire resistivity was measured within 130 kΩ (5 µm width) and 3 GΩ (300 nm width).
Ion induced graphitization of ta-C films by FIB offers prospective applications in nano technology to fabricate conductive nanostructures in an insulating thin film.