The relation between the average diameter of CNTs on Ni–Cu @ a‐C:H catalyst with the optical absorption edge and the optical dispersion parameters.

Summary: In this study, the average diameter of the grown CNTs on Ni–Cu NPs @ a‐C:H substrates were increased by increasing of Cu content. The obtained results indicated that by increase of Cu content, all films exhibited high‐absorption spectra; therefore, we were facing an increase in the energy gap of films. The values of dT/dλ and dR/dλ measurements for grown CNTs with 75% Cu shown that maximum values of optical band gap correspond to with values of 2.48 eV and 2.90 eV, respectively. It can be seen that with increase of average diameter of the grown CNTs, the values of Urbach energy of films were increased. The RBS and EDAX measurements were confirmed presence of Ni and Cu atoms into films. The films deposited with 75% Cu were more smooth. Films deposited with 75% Cu have more disordered. Films deposited with 75% Cu atoms have maximum values of the oscillator strength f and the dispersion energy Ed about of 0.108 eV2 and 0.0543 eV, respectively. [ABSTRACT FROM AUTHOR]