“…Amorphous carbon lms were obtained via DC-magnetron sputtering (Torr International) from a graphite target (99.999%) at base pressures <2 Â 10 À6 mbar, deposition pressures 2-7 Â 10 À3 mbar and total gas ow of 50 mL min À1 , following previously reported protocols. 14,15 Briey, nitrogenated amorphous carbon lms (a-C:N) were obtained by using N 2 /Ar gas at ow ratios of 2%, 5% and 10% while keeping deposition time constant at 40 min, whereas non-nitrogenated amorphous carbon (a-C) was obtained by carrying out the deposition using 100% Ar during deposition. Electrodes thus deposited are topographically smooth; the mean thickness was determined via spectroscopic ellipsometry, following methods detailed in our previous work, 14,16,17 to be 74, 83, 114 and 123 nm for a-C, a-C:N-2%, 5% and 10%, respectively (see ESI †).…”