Abstract
We studied electromagnetic properties of pyrolytic carbon (PyC) films with thicknesses from 9 nm to 110 nm. The PyC films consisted of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers were synthesized by chemical vapor deposition (CVD) at 1100 °C on a quartz substrate. The reflectance and transmittance of these films in Ka-band, 26–37 GHz, were studied both experimentally and theoretically. The discovered remarkably high absorption loss of up to 50% of incident power, along with chemical stability, makes PyC films attractive for electromagnetic (EM) interference shielding in space and airspace communication systems, as well as in portable electronic devices occupying this frequency slot. Since, in practical applications, the PyC film should be employed for coating of dielectric surfaces, two important issues to be addressed are: (i) which side (front or back) of the substrate should be covered to ensure maximum absorption losses; and (ii) the frequency dependence of absorbance/transmittance/reflectance of binary PyC/quartz structures in the Ka-band.
Highlights
As the microwave (MW) spectrum becomes more and more crowded, which is synonymous with an increasing electromagnetic (EM) compatibility problem [1], one needs new functional materials for EM coatings, shields and filters, working in specific frequency bands
We have recently suggested an interesting alternative to graphene-based materials by demonstrating that 25 nm thick pyrolytic carbon (PyC) film, which is morphologically close to the nanographite, being many thousands times thinner than skin depth can attenuate a significant part of incident microwave radiation [5]
The measured and calculated reflectance, transmittance and absorbance are presented in Figure 3 for films being 75 nm and 110 nm thick and in Table 2 for thinner films (9 nm, 20 nm and 30 nm)
Summary
As the microwave (MW) spectrum becomes more and more crowded, which is synonymous with an increasing electromagnetic (EM) compatibility problem [1], one needs new functional materials for EM coatings, shields and filters, working in specific frequency bands. Such materials should combine high electrical conductivity with good electromagnetic interference (EMI) shielding efficiency (SE), the reciprocal of the transmittance. We have recently suggested an interesting alternative to graphene-based materials by demonstrating that 25 nm thick pyrolytic carbon (PyC) film, which is morphologically close to the nanographite, being many thousands times thinner than skin depth can attenuate a significant part of incident microwave radiation [5].
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