Van der Waals Epitaxy of Two-Dimensional MoS2鈥揋raphene Heterostructures in Ultrahigh Vacuum

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• 作者：Jill A. Miwa ; Maciej Dendzik ; Signe S. Gr酶nborg ; Marco Bianchi ; Jeppe V. Lauritsen ; Philip Hofmann ; S酶ren Ulstrup
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：9
• 期：6
• 页码：6502-6510
• 全文大小：983K
• ISSN：1936-086X

文摘

In this work, we demonstrate direct van der Waals epitaxy of MoS₂鈥揼raphene heterostructures on a semiconducting silicon carbide (SiC) substrate under ultrahigh vacuum conditions. Angle-resolved photoemission spectroscopy (ARPES) measurements show that the electronic structure of free-standing single-layer (SL) MoS₂ is retained in these heterostructures due to the weak van der Waals interaction between adjacent materials. The MoS₂ synthesis is based on a reactive physical vapor deposition technique involving Mo evaporation and sulfurization in a H₂S atmosphere on a template consisting of epitaxially grown graphene on SiC. Using scanning tunneling microscopy, we study the seeding of Mo on this substrate and the evolution from nanoscale MoS₂ islands to SL and bilayer (BL) MoS₂ sheets during H₂S exposure. Our ARPES measurements of SL and BL MoS₂ on graphene reveal the coexistence of the Dirac states of graphene and the expected valence band of MoS₂ with the band maximum shifted to the corner of the Brillouin zone at K虆 in the SL limit. We confirm the 2D character of these electronic states via a lack of dispersion with photon energy. The growth of epitaxial MoS₂鈥揼raphene heterostructures on SiC opens new opportunities for further in situ studies of the fundamental properties of these complex materials, as well as perspectives for implementing them in various device schemes to exploit their many promising electronic and optical properties.