title: Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy.
abstract: Two-dimensional (2D) heterostructures hold the promise for future atomically thin electronics and optoelectronics because of their diverse functionalities. Although heterostructures consisting of different 2D materials with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) epitaxy, constructing heterostructures from layered semiconductors with large lattice misfits remains challenging. We report the growth of 2D GaSe/MoSe2 heterostructures with a large lattice misfit using two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2 heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between the two layers, forming a periodic superlattice. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2 crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2 monolayer domains in lateral GaSe/MoSe2 heterostructures, GaSe monolayers are found to overgrow MoSe2 during CVD, forming a stripe of vertically stacked vdW heterostructures at the crystal interface. Such vertically stacked vdW GaSe/MoSe2 heterostructures are shown to form p-n junctions with effective transport and separation of photogenerated charge carriers between layers, resulting in a gate-tunable photovoltaic response. These GaSe/MoSe2 vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Xufan
authors.initials: X
authors.lastname: Li
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Ming-Wei
authors.identifier: 0000-0001-8150-5585
authors.initials: MW
authors.lastname: Lin
authors.affiliation: Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Junhao
authors.initials: J
authors.lastname: Lin
authors.affiliation: Beijing Computational Science Research Center, Beijing 100094, China.; Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Huang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Ma
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Wu
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Sokrates T
authors.identifier: 0000-0002-2963-7545
authors.initials: ST
authors.lastname: Pantelides
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Miaofang
authors.identifier: 0000-0003-0764-1567
authors.initials: M
authors.lastname: Chi
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Kravchenko
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Jason
authors.identifier: 0000-0002-6295-5115
authors.initials: J
authors.lastname: Fowlkes
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rouleau
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: David B
authors.identifier: 0000-0003-0273-3139
authors.initials: DB
authors.lastname: Geohegan
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Xiao
mesh_terms: D003460:Crystallization; D005708:Gallium / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D045663:Quantum Dots / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry*
chemical_list: C517764:gallium selenide; D008982:Molybdenum; D005708:Gallium; D012643:Selenium
keywords: Two-dimensional; heterostructure; lattice-misfit; photovoltaic; van der Waals epitaxy