The effect of Cu content in MWCNTs synthesized by Ni - Cu @ a-C:H catalyst on the optical constants and the optical loss

Abstract

In this paper, Ni-Cu NPs @ a-C:H films with different Cu content, by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition (RF-PECVD) were prepared using acetylene gas and Ni and Cu targets. We studied optical constants of MWCNTs synthesized, with constant Ni content and different percentages of 5, 40 and 75 % from Cu atoms. With increase of Cu content, the average diameter of MWCNTs were increased however the RMS roughness of films were decreased. It is found that the absorption coefficients of films deposited with 5% Cu have maximum value. Also it can be seen that the minimum values of the optical band gaps of films happen in films deposited with 5% Cu. With increase of Cu content, the values of energy loss by the free charge carriers were increased however the plasma frequency ωp and free charge carriers concentration N/m* of films were decreased. The free carriers electric susceptibility χc at in films deposited with 75 % Cu has maximum value. The values of the ratio of free charge carriers concentration to effective mass, N/m*, in films deposited with 5% Cu has maximum value about of 423.731048 m−3 kg−1.