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 degreesC) by using scanning tunneling microscopy and x-ray photoelectron spectroscopy. At 900 degreesC, a crystalline silicate structure transforms into a bulklike (1 X 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 degreesC, 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 (similar to2.3 Angstrom) of the (1 X 1) unit length along the <110> directions. (C) 2002 American Vacuum Society.