Multiple phase structures of Hf silicide precipitated from Hf silicate: An atomic view

Multiple phase structures of crystalline hafnium silicide precipitated from the silicate have been found as a function of temperature $(900–1000 °C)$ by using scanning tunneling microscopy and x-ray photoelectron spectroscopy. At $900 °C,$ a crystalline silicate structure transforms into a bulklike $(1×1)$ “facetbar” of $HfSi2$ near the topmost surface, but into a “platelet” around the interface with Si. A Si-depletion zone is found to only form near platelets, not facetbars. Upon further annealing to $1000 °C,$ facetbars likely transform into platelets, and the atomic structure of a platelet also transforms to a patchlike feature having two equivalent antiphase sites, which are shifted by a half $(∼2.3 Å)$ of the $(1×1)$ unit length along the $〈110〉$ directions.