Effectiveness of electromagnetic interference shielding of sputtered nitrogen -doped carbon thin films

In this work, nitrogen-doped carbon (C:N) films are deposited on the aluminum/polyethylene terephthalate substrate by RF magnetron sputtering with different N-2 flow rates. Film properties are characterized by transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrical properties are examined by Hall measurements, and the shielding efficiency is extracted from the network analyzer in the frequency range of 8.2-12.4 GHz. The Raman spectra suggest that N introduction in carbon films increases the intensity ratio of D-band (ID) to G-band (IG). A blue shift of the G-band is also observed. The Hall measurement reveals that the N doping acts as electron donor, leading to an increase in carrier concentrations and conductivity. Due to the improvement of electrical properties, more carriers interact with the incident EM field, resulting in an increased absorption loss through the C:N films. The electromagnetic interference shielding effectiveness, in terms of reflection loss and absorption loss, increases as well.