Diamond synthesis in oxygen‐acetylene flames: Inhomogeneities and the effects of hydrogen addition

Micro‐Raman spectroscopy, scanning electron microscopy and a surface density counting technique have been used to probe the inhomogeneities of diamond crystallites grown with an oxygen‐acetylene flame on a scratched Si(100) surface. The surface temperature profile was measured using a thermal imaging camera and compared with the observed inhomogeneities in the diamond crystallites. It is concluded that the flame species flux to the surface is the dominant factor contributing to the diamond crystallite inhomogeneities. Hydrogen addition to the oxygen‐acetylene flame was studied. The addition of hydrogen reduced the amount of ‘‘amorphous’’ carbon contained in the diamond crystallites as measured with Raman spectroscopy. Growth density profiles were determined as a function of the inner flame front to substrate distance. For uniform growth density in the oxygen‐acetylene flame the substrate must be placed in the acetylene feather at a sufficient distance from the inner flame to avoid annular growth.

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