Search

We have analyzed the growth process of a-C:H nanoparticles in Ar–C2H2 and Ar–CH4 plasmas by means of in situ Rayleigh-Mie scattering ellipsometry. Complex refractive index (m=n−ki), mean particle radius (r), and particle size distribution (σ) of a-C:H nanoparticles are carefully determined and compared with those of a-C:H thin films deposited at similar conditions. It is found that, in both plasmas, small particles (r

The roughness evolution during plasma deposition of amorphous hydrogenated carbon (a-C:H) films is investigated. Films were deposited from an inductively coupled methane plasma using a wide range of process parameters. Plasma deposition is uniquely described by the dissipated energy per source gas molecule Emean. Depending on Emean, a specific set of radicals contributes to film growth causing a characteristic roughness development. The film roughness is measured using atomic force microscopy and spectroscopic ellipsometry and is expressed using the static and dynamic scaling coefficients α and β, respectively. For low Emean 20eV, α∼0.9 and β∼0.25 indicating film deposition via a growth precursor with a small surface diffusion length.

We present the Raman spectra of amorphous hydrogenated carbon nanoparticles prepared in an Ar–CH4 hydrocarbon plasma. The measured Raman spectra are compared with that of both soft polymerlike and hard diamondlike a-C:H films deposited from pure CH4 plasma. The film properties were studied by Rutherford backscattering and spectroscopic ellipsometry. It is shown that the plasma characteristics are continuously changed from a “precursor-rich” state to a “precursor” state during the particle formation process. As a result, the net flux of the carbon atoms to the surface of the nanoparticles (growth rate) decreases linearly as a function of time as the nanoparticles are growing up. Also, the hydrogen content in nanoparticles increases as a function of nanoparticle size. The particle growth process is then examined by a simple ballistic model. It is found that the volume polymerization process, i.e., the growth of the nanoparticles at a large particle size (⩾100nm), is essentially the same as the surface polym...