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Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P172
Phase transition of β − MoTe2 studied by temperature-dependent angleresolved
photoemission spectroscopy
Robert Heimburger 1 , Thorsten Zandt, Recardo Manzke
1 Humboldt-Universität zu Berlin, Institut für Physik, Newtonstr. 15, 12489 Berlin
The β-type of the polymorph material MoTe2 grown by chemical vapor transport at
temperatures above 900 ◦ C shows a layered structure which can be described as stacked
sandwiches of the tree layers Te-Mo-Te. Therefore, the crystals exhibit distinct twodimensional
behavior.
At room temperature β − MoTe2 has a monoclinic crystal structure. The Te atoms
are placed around the metal atom in a slightly distorted octahedron and therefore the
metal atoms form zigzag-chains along the crystallographic x2 direction. By cooling
below 250K, β − MoTe2 undergoes a phase transition, where the monoclinic angle of
the high temperature phase changes from 93 ◦ 55” to 90 ◦ , resulting in an orthorhombic
structure.
In this contribution we present a detailed temperature dependent study of electronic
band structure of β − MoTe2 performed by angle-resolved photoemission spectroscopy
(ARPES). The measurements were carried out at the BUS undulator beamline at
BESSY II supplemented by data taken with HeI radiation. It results that the dispersions
of the valence bands along the different high-symmetric directions of the Brillouin
zone are extremely weak except for the bands very close to the Fermi level. These bands
reveal close insight into the low temperature and phase transition behavior of quasitwo
dimensional materials like β −MoTe2. The experimental findings will be compared
with additional tight-binding band structure calculations.