Seminars Archive

STM Imaging of buried-metal layer in TMD surfaces and (211) oriented heteroepitaxial growth of Ag and Au

Abstract
There is controversy in the literature concerning the STM images of TMD (Transition Metal Di-chalcogenide) surfaces in which the contributions of surface chalcogen and sub-surface metal atoms are not clear. On a- and b-MoTe2 (001) surfaces, it is found that the buried-metal atoms can be imaged by STM when tip is closed to the surface while scanning near the Fermi level. When tip is far from the surface only chalcogen atoms can be observed. Thus, it becomes possible to image selectively either metal or chalcogen atoms and investigations were further extended into WTe2, NbTe2, WSe2 and NbSe2 (001) surfaces. Further, to understand the substrate atomic geometry influence on the nucleation and growth process of FCC metals, the growth of Ag and Au on a- and b-MoTe2 (001) surfaces have been investigated by using STM, AFM and TEM/TED. On atomically flat a-MoTe2 surface, n-n distances of Au atoms in 2D Au clusters are found to be cluster-size dependent at very low Au coverages. On b-MoTe2 surface, in addition to the formation of anisotropic islands due to preferential 1D adatom diffusion along the Te troughs, the orientation of both epitaxial layers are found to be (211) which is differ from the characteristic (111) growth of FCC metals on TMD surfaces.