Effect of deposition pressure on the electrical properties of nitrogen-doped amorphous carbon films

In this study, we investigate the effect of the deposition pressure on the electrical properties of nitrogen-doped amorphous carbon (a-C:N) films deposited by using an unbalanced DC magnetron sputtering method. As the deposition pressure is decreased from 9 to 1 mTorr, the resistivity decreases from 7.88 to 2.68 × 10 ⁻² Ω·cm while the deposition rate increases from 3.5 to 4.4 nm/min. The decrease in resistivity is caused by increases in both the carrier concentration and mobility. As the pressure is decreased, the carrier concentration increases from 1.9 × 10¹⁴ to 7.8 × 10²⁰ cm ⁻³, and the mobility increases from 0.01 to 0.3 cm²/V·sec. X-ray photoelectron spectroscopy and Raman spectroscopy reveal that the improved electrical properties of the film deposited at a lower pressure are the result of a higher fraction of sp² bonding.