We have studied the emission spectra from plasmas excited in several compositions of three different gas mixtures useful for the growth of diamond films, namely CH4-H-2 (the classical one), CH4-CO2 and C2H2-CO2 (not previously reported by other authors). In all three cases we find the same correlation between the quality of the obtained diamond films and some spectral features: in particular, the yield of the best diamond films corresponds to the presence of the emission line at wavelength 431 nm ascribed to CH, in the absence of the emission band at 505-517 nm attributed to C2. The appearance and the progressive increase of the latter corresponds to a gradual worsening of the diamond film quality. We propose such spectral features of the plasma as a general and practical gauge of the diamond film growth conditions, for any gas mixture used
A critical experimental test of the empirical unifying scheme recently proposed by Bachmann, Leers, and Lydtyn [Diamond and Related Mater. 1, 1 (1991)] about the gas compositions useful to grow diamond films by plasma-assisted chemical-vapor deposition has been performed. The data confirm the main concept of the Bachmann scheme, namely, the existence of a single compositional" diamond domain" in a C-O-H triangular diagram, in which the overall gas compositions are plotted; however, quantitatively, the shape and the borders of such a diamond domain are rather different from those assumed in the work of Bachmann and co-workers. For all the gas mixtures investigated, the changes in the plasma optical emission spectra consequent to crossing the border from the"no-growth zone" into the"diamond domain" have been studied. These changes show universal features, which point to the presence of the same growth mechanisms over all the diamond domain, independent of the identity of the initial chemical species
We report a novel technique to grow crystals of the high-temperature superconductor Bi2Sr2Ca2Cu3O10+x and Bi2Sr2CaCu2O8+x (2223 and 2212 BSCCO phases), both pure and Pb substituted. The technique, based on chemical transport in a thermal gradient in molten KCl, is simple and inexpensive, and yields a continuous output of crystals, with growth times of a few minutes, i.e., orders of magnitude shorter than conventional flux methods. Depending on melt aging, crystals of either the pure 2223 or the pure 2212 BSCCO phases are obtained, having zero-resistance temperature of 105 and 90 K, respectively, and a transport critical current density of 104 A cm−2 at liquid nitrogen temperature.
Abslrad-Thin f i l m s of lithium-zinc ferrite have been grown by pulsed laser deposition techniques under varying oxygen partial pressures. X-ray diffraction measurements showed the films grew epitaxially onto the (001) MgO substrates. Films grown at lower oxygen pressures displayed cubic anisotropy with parameters close to bulk values, with the film grown at the lowest pressure having the highest saturation magnetization and the narrowest ferromagnetic resonance linewidth. The film grown at the highest pressure displayed in-plane uniaxial anisotropy and a relatively low magnetization.
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