Synthesis of nanostructure carbon thin films by microwave plasma-enhanced chemical vapor deposition

Abstract

In this work, hydrogenated amorphous carbon (a-C:H) thin films were prepared from methane gas using microwave plasma enhanced chemical vapor deposition (MPECVD). The microwave plasma system was built in our laboratory with maximum attained plasma electron temperature and density of (0.65 eV) and (1.45 × 1018 cm−3), respectively. The effect of argon/methane mixing ratio on the optical and structural properties of the films were investigated. X-ray diffraction results indicated a broad peak ranging from 15 to 35 in 2θ angle confirm the amorphous nature of the deposited carbon films. While, FTIR measurements revealed the existence of (a-C:H) through its absorption peak. AFM was used to study the morphological characteristics and to monitor the nanostructure under the influence of different mixing ratios of argon with methane. The distribution of granularity ranged from 30 to 140 nm, and the particles average diameter were 94.39–81.92 nm, also the root mean square roughness was increased with the increasing of the argon/methane mixing ratio. The optical energy gap (Eg) decreased from 2.76 to 2.40 eV with increasing deposition pressure from 0.5 to 1.5 mbar and varying the argon/methane mixing ratio.