Tricriticality in the orientational phase diagram of stepped Si(113) surfaces

An x-ray scattering study is presented of the orientational phase diagram of Si surfaces misoriented by up to 6[degree] from the cubic [113] direction towards [001] and for temperatures between 300 and 1500 K. At the highest temperatures, the surface is uniformly stepped. Below [ital T][sub [ital t]]=1223 K, there is a two phase region in which (113) facets appear in coexistence with the stepped phase. We identify [ital T][sub [ital t]] as a tricritical point. For temperatures between a triple point at [ital T][sub 3]=1134 K and 300 K, coexistence between the (113) facet and the (114) facet is found.