350-nm-wavelength laser ablation of ceramic SiC targets has been used to deposit SiC films on fused silica and R-cut sapphire at substrate temperatures from 300 to 1150 °C. The films deposited above 800 °C show (111) and (222) x-ray-diffraction bands from crystal planes parallel to the substrate. The bandwidths decrease and the integrated intensities increase with deposition temperature. The crystallite dimension for the highest-temperature films is in the order of 50 nm. The diffraction peaks are absent for the films deposited at the lower temperatures. Analysis of optical transmission spectra of the high-temperature films shows a lowest-energy gap near 2.2 eV which is the value for cubic SiC. The low-temperature films show smaller and variable gaps. The room-temperature resistivities of the former are low, from 0.02 to 0.1 Ω cm whereas the latter are insulating. Film thicknesses and deposition rates ranging from 0.2 to over 0.6 Å/pulse are obtained from the spectra and by monitoring of the interference oscillations in the infrared emission through the film during deposition.
The temperature dependence of the Seebeck coefficient of polycrystalline β-SiC films deposited on quartz substrates by laser ablation and of commercially available α-SiC wafers is reported in a temperature range of 300-533 K for the first time. The Seebeck emf of α-SiC substrates and β-SiC samples ranges between −9 µV • C −1 and −108 µV • C −1 which is higher than that of commercial Pt thermocouples.
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