Papers
Topics
Authors
Recent
Gemini 2.5 Flash
Gemini 2.5 Flash
173 tokens/sec
GPT-4o
7 tokens/sec
Gemini 2.5 Pro Pro
46 tokens/sec
o3 Pro
4 tokens/sec
GPT-4.1 Pro
38 tokens/sec
DeepSeek R1 via Azure Pro
28 tokens/sec
2000 character limit reached

Spin splitting and strain in epitaxial monolayer WSe$_2$ on graphene (1912.04770v1)

Published 10 Dec 2019 in cond-mat.mtrl-sci

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 $\overline{\mathrm{K}}$ was $\Delta_\mathrm{SO}=0.469\pm0.008$ eV by angle-resolved photoemission spectroscopy (ARPES). Synchrotron-based grazing-incidence in-plane X-ray diffraction (XRD) revealed the in-plane lattice constant of monolayer WSe${2}$ to be $a\mathrm{WSe_2}=3.2757\pm0.0008 \mathrm{\r{A}}$. This indicates a lattice compression of -0.19 % from bulk WSe${2}$. By using experimentally determined graphene lattice constant ($a\mathrm{MLG}=2.4575\pm0.0007 \mathrm{\r{A}}$), we found that a 3$\times$3 unit cell of the slightly compressed WSe${2}$ is perfectly commensurate with a 4$\times$4 graphene lattice with a mismatch below 0.03 %, which could explain why the monolayer WSe${2}$ is compressed on MLG. From XRD and first-principles calculations, however, we conclude that the observed size of strain is negligibly small to account for a discrepancy in $\Delta_\mathrm{SO}$ found between exfoliated and epitaxial monolayers in earlier ARPES. In addition, angle-resolved, ultraviolet and X-ray photoelectron spectroscopy 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.

Citations (13)

Summary

We haven't generated a summary for this paper yet.