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Spin splitting and strain in epitaxial monolayer WSe2 on graphene
DOI:
10.1103/PhysRevB.101.165103
Authors:
H.
Nakamura
(Max Planck Institute for Solid State Research)
,
A.
Mohammed
(Max Planck Institute for Solid State Research)
,
Ph.
Rosenzweig
(Max Planck Institute for Solid State Research)
,
K.
Matsuda
(Max Planck Institute for Solid State Research; Nagoya University)
,
K.
Nowakowski
(Max Planck Institute for Solid State Research; University of Twente)
,
K.
Küster
(Max Planck Institute for Solid State Research)
,
P.
Wochner
(Max Planck Institute for Solid State Research)
,
S.
Ibrahimkutty
(Max Planck Institute for Solid State Research)
,
U.
Wedig
(Max Planck Institute for Solid State Research)
,
H.
Hussain
(Diamond Light Source)
,
J.
Rawle
(Diamond Light Source)
,
C.
Nicklin
(Diamond Light Source)
,
B.
Stuhlhofer
(Max Planck Institute for Solid State Research)
,
G.
Cristiani
(Max Planck Institute for Solid State Research)
,
G.
Logvenov
(Max Planck Institute for Solid State Research)
,
H.
Takagi
(Max Planck Institute for Solid State Research; University of Tokyo; University of Stuttgart)
,
U.
Starke
(Max Planck Institute for Solid State Research)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Physical Review B
, VOL 101
State:
Published (Approved)
Published:
April 2020
Diamond Proposal Number(s):
18887

Abstract: We present the electronic and structural properties of monolayer WSe 2 grown by pulsed-laser deposition on monolayer graphene (MLG) on SiC. The spin splitting in the WSe 2 valence band at ¯¯¯ K was Δ SO = 0.469 ± 0.008 eV, as determined by angle-resolved photoemission spectroscopy. Synchrotron-based grazing-incidence in-plane x-ray diffraction (XRD) revealed the in-plane lattice constant of monolayer WSe 2 to be a WSe 2 = 3.2757 ± 0.0008 Å. This indicates a lattice compression of − 0.19 % relative to bulk WSe 2 . By using the experimentally determined graphene lattice constant ( a MLG = 2.4575 ± 0.0007 Å), we found that a 3 × 3 unit cell of the slightly compressed WSe 2 is perfectly commensurate with a 4 × 4 graphene lattice with a mismatch below 0.03%, which could explain why the monolayer WSe 2 is compressed on MLG. From XRD and first-principles calculations, we conclude that the observed size of strain will affect Δ SO only on the order of a few meV. In addition, angle-resolved, ultraviolet, and x-ray photoelectron spectroscopies shed light on the band alignment between WSe 2 and MLG/SiC and indicate electron transfer from graphene to the WSe 2 monolayer. As further revealed by atomic force microscopy, the WSe 2 island size depends on the number of carbon layers on top of the SiC substrate. This suggests that the epitaxy of WSe 2 favors the weak van der Waals interactions with graphene, while it is perturbed by the influence of the SiC substrate and its carbon buffer layer.
Journal Keywords: Electronic structure; Spin-orbit coupling; Spintronics; Transition-metal dichalcogenide; Angle-resolved photoemission spectroscopy; First-principles calculations; Grazing incidence X-ray diffraction
Subject Areas:
Materials,
Physics
Instruments:
I07-Surface & interface diffraction
Documents:
PhysRevB.101.165103.pdf
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