Influence of Fe-doped on structural, electronic structural and optical properties of hydrogenated amorphous carbon films prepared by plasma enhanced chemical vapor deposition

Abstract

Fe-doped hydrogenated amorphous carbon (a-C:H:Fe) films were deposited from an isobutene/ferrocene/H 2 gas mixture by plasma enhanced chemical metal organic vapor deposition. Raman spectra were used to characterize the bonding structure of the a-C:H:Fe films and hydrogenated amorphous carbon (a-C:H) films. Optical properties were investigated by the UV–vis spectroscopy and the photoluminescence spectra. The number of six-numbered rings of the a-C:H films increases and sp 2 clustering of the films decreases after Fe-doping. The Tauc optical gap of the a-C:H:Fe films becomes narrower by 0.15–0.23 eV relative to the value of the a-C:H films. The narrowing of the optical gap after doping is attributed primarily to the extended state around the Fe deep level in the band gap and the narrowing of the π and π * band edge states because of the increase of the number of six-numbered rings in the a-C:H films. Fe deep level defects of the a-C:H:Fe films contribute chiefly to non-radiative recombination.