Laser-induced carbon CVD on a moving fused quartz substrate: morphological and oscillatory deposition characteristics

摘要

CO_2 Laser-induced chemical vapor deposition (LCVD) is being investigated as a possible technique of depositing uniform carbon coatings on moving fused quartz substrates. A CO_2 laser is used to locally heat the substrate surface and create a hot spot where pyrolysis of hydrocarbon species occurs and subsequently deposits a layer of carbon film. The results indicate that uniform carbon film stripes can be deposited on moving fused quartz rods using pyrolytic LCVD only under certain deposition conditions, otherwise oscillation of the stripe width or substrate damage by laser radiation will occur. The transition region for oscillation, as well as the period of oscillation, is identified. Substrate damage can be induced by reducing the laser spot size, even when the substrate receives a lower irradiation intensity. Raman spectra of the carbon film stripes indicate that the film consists of disordered graphitic material. The ratio of the D-peak to the G-peak intensity found in the Raman spectrum is used to characterize the degree of disorder for the carbon film. The range of the Raman peak ratios is 0.795-0.935.