SCANNING TUNNELING MICROSCOPE INVESTIGATION OF THE GROWTH-MORPHOLOGY OF TITANIUM SILICIDE ON SI(111) SUBSTRATES

A scanning tunneling microscope in ultrahigh vacuum has been used to investigate the growth, morphology, and surface atomic structure of ultrathin titanium silicide films on Si(111) substrates. Microstructural considerations have been used to identify various stages of the silicide growth. Atomic resolution images of a titanium silicide crystallite facet, formed at 850 degrees C, have been identified as a 2X2 silicon termination of a C54-TiSi2(010) surface. Possible epitaxial silicide/silicon relationships are provided. Theoretical consideration has been given to the interatomic bonding in the C54-TiSi2 lattice and the dangling bond density of ideally terminated silicide planes has been calculated. The highly reconstructed atomically flat surface of a large crystallite, formed at 1200 degrees C, has been assigned as a C54-TiSi2(311) plane giving the epitaxial relation C54-TiSi2(311)parallel to Si(111). The presence of pairs and linear chains of defects, with common orientations, is attributed to the decomposition of a diatomic gas on the facet, producing sites of preferential adsorption on the silicide surface. (C) 1995 American Institute of Physics.