Investigation of conducting nanostructures on ta-C films made by FIB lithography

DFG – project BI 508 / 13-1      04/2010 – 08/2013   Dr. Peter Philipp

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.