Regensburg 2000 – wissenschaftliches Programm

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O: Oberflächenphysik

O 11: Postersession (Eröffnung)

O 11.22: Poster

Montag, 27. März 2000, 19:00–22:00, Bereich C

Determination of the polytype of epitaxial TaS₂ — •Christian Kreis, Sascha Werth, Rainer Adelung, Jörn Kanzow, Lutz Kipp, and Michael Skibowski — Leibnizstrase 19, 24118 Kiel

Determination of the polytype of epitaxial TaS₂

Thin epitaxial films in the submonolayer regime up to a few

monolayers of the layered transition metal dichalcogenide

(TMDC) TaS₂ were grown on metallic and semiconducting TMDCs by

van der Waals epitaxy. The coordination of the tantalum and

sulfur atoms in one layer, that can be either octahedral

(1T polytype) or trigonal prismatic (2H polytype), is crucial

for the formation of charge density waves (CDWs) and the

electronic structure around Fermi level. While the 1T polytype of

bulk TaS₂ already shows CDWs at room temperature the 2H polytype

is susceptible to CDWs only below 76K. Further on, both polytypes

exhibit different phase diagrams with changing temperature.

Thus temperature dependent ultra-violet photoemission

spectroscopy and X-ray photoemission spectroscopy were applied

to epitaxial TaS₂ and compared with measurements of 1T and 2H

TaS₂ bulk crystals to give insight into the coordination of the

epitaxial layers and the existence of CDWs. The geometrical

structure of the TaS₂ layers was characterized using scanning

tunneling microscopy.