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

Tetrahedral amorphous carbon (ta-C) films with high sp3 content 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 was applied to describe the swelling for Ga+ irradiated ta-C films for fluences up to 1 × 1016 cm−2 and was extended to higher fluences using TRIDYN simulations and taken into account sputtering. Van-der-Pauw structures were produced by means of Ga+ FIB lithography. A decrease of the sheet resistance with increasing fluence due to the evolution of graphitic regions was observed. The lowest value of 290 Ω sq−1 was achieved at 1.6 × 1017 cm−2. The resistance of graphitic nano-wires was measured within 109 Ω and 107 Ω for different irradiation fluences. Irradiations under elevated temperatures show Ga segregation starting at 300 °C that promises changes in electrical properties and morphology.