title: Epitaxial 2D MoSe2 (HfSe2) Semiconductor/2D TaSe2 Metal van der Waals Heterostructures.
abstract: Molecular beam epitaxy of 2D metal TaSe2/2D MoSe2 (HfSe2) semiconductor heterostructures on epi-AlN(0001)/Si(111) substrates is reported. Electron diffraction reveals an in-plane orientation indicative of van der Waals epitaxy, whereas electronic band imaging supported by first-principles calculations and X-ray photoelectron spectroscopy indicate the presence of a dominant trigonal prismatic 2H-TaSe2 phase and a minor contribution from octahedrally coordinated TaSe2, which is present in TaSe2/AlN and TaSe2/HfSe2/AlN but notably absent in the TaSe2/MoSe2/AlN, indicating superior structural quality of TaSe2 grown on MoSe2. Apart from its structural and chemical compatibility with the selenide semiconductors, TaSe2 has a workfunction of 5.5 eV as measured by ultraviolet photoelectron spectroscopy, which matches very well with the semiconductor workfunctions, implying that epi-TaSe2 can be used for low-resistivity contacts to MoSe2 and HfSe2.
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Tsoutsou
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.|University of Athens , Department of Physics, Section of Solid State Physics, 15684 Athens, Greece.
authors.forename: Kleopatra E
authors.initials: KE
authors.lastname: Aretouli
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.
authors.forename: Polychronis
authors.initials: P
authors.lastname: Tsipas
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.|National Technical University of Athens , Department of Physics, 15780 Athens, Greece.
authors.forename: Jose
authors.initials: J
authors.lastname: Marquez-Velasco
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Xenogiannopoulou
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Kelaidis
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.|University of Athens , Department of Physics, Section of Solid State Physics, 15684 Athens, Greece.
authors.forename: Sigiava
authors.initials: S
authors.lastname: Aminalragia Giamini
authors.affiliation: Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", 15310 Athens, Greece.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Dimoulas
keywords: HfSe2; MoSe2; TaSe2; metal/semiconductor contacts; molecular beam epitaxy; van der Waals heterostructures