First-principle Study Of Amorphous Carbon And Fabrication Of Its Film

a-C film is charactereized by its interesting physical and chemical properties thatmake it suitable for many applications. Currently, numerous experiments about thestructure and properties of a-C film have been investigated, but few researches study itsinternal mechanism. In the article we present a-C and a-C:Si model from atomic scale,aiming at investigating further the structural and photoelectric properties of the models; Atthe same time, some feasible researches are analyzed for the prepared a-C film.The first-principle and mlecular dynamics methods is adopted to build a-C structuralmodels covering a range of densities, the analysis of the models reveals that dangling bondexist in all model structures, the isolated sp1atoms is found in the2.0-g/cm3~2.6-g/cm3structure, the sp3danging bonds mainly exisy in the high-density structure, and thenonlinar dependence of stress on sp3fraction is observed. The electronic density of EFlevel decrease with the increasing density, and this has the effect of widening the band gap.The transmittance of a-C increase with the increasing density outing of the2.3-g/cm3structure in visible and near infrared wave band, and the optical band gap also increasewith the density. Samples of2.0-g/cm3and2.9-g/cm3structure doped by1.6%and3.2%of silicon have been studied, the study show that a small amount of silicon can generatemore sp3hybridized atoms and reduce internal stress. Meanwhile the local density of stateof silicon without forming a peak in EF, but the transmittance is changed. A small fractionof silicon is helpful to increase the transmittance in near ultraviolet-visible-near infraredwave band for2.0-g/cm3structure, but the tendency is not suitable for the2.9-g/cm3tetrahedral amorphous carbon. On the whole, the samples of a-C doped by3.2%of siliconis always higher than the samples doped by1.6%in the transmittance.a-C film is prepared using magnetron sputtering technology, reasonable conclusionscan be drawn. The particles in the film gradually increase with the increase of sputteringpower, and gather together to form clusters; higher Ar gas flow is advantageous to thegeneration of tiny island particles. The sputtering power smaller and Ar gas flow increaser,the transmittance higher. The highest transmittance of the prepared films is about92%. In addition, a-C film has good adhesion to the substrate, this due to the chemical bondingforce and mechanical interlocking between the film and substrate.