Glancing incidence diffraction studies of titanium carbide single crystal surfaces in ultra high vacuum environment

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Abstract
Reflection mode high energy electron diffraction has been used to study the (110) and (001) planes of titanium carbide in an ultra high vacuum environment. The (110) surface forms into {100} facets after only a moderate amount of heating. The formation of facets is suppressed by the presence of carbon monoxide in the vacuum environment. Under certain heating conditions a superlattice, probably composed of carbon vacancies, forms in the sub-surface region near the (110) surface. This superlattice is not observed in the (001) sub-surface region. The mechanism of the formation of facets is postulated to involve the loss of carbon from the substrate as CO and the removal of titanium by - evaporation from a titanium-rich surface region. This model leads to an acceptable value for the rate of facet growth and is supported by measurements of changes in the TiC lattice parameter.