Molecular Beam Epitaxy of a 2D Material Nearly Lattice Matched to a 3D Substrate: NiTe₂ on GaAs

Abstract

The lattice mismatch between interesting 2D materials and commonly available 3D substrates is one of the obstacles in the epitaxial growth of monolithic 2D/3D heterostructures, but a number of 2D materials have not yet been considered for epitaxy. Here, we present the first molecular beam epitaxy growth of a NiTe2 2D transition-metal dichalcogenide. Importantly, the growth is realized on a nearly lattice-matched GaAs(111)B substrate. Structural properties of the grown layers are investigated by electron diffraction, X-ray diffraction, and scanning tunneling microscopy. Surface coverage and atomic-scale order are evidenced by images obtained with atomic force, scanning electron, and transmission electron microscopy. Basic transport properties were measured confirming that the NiTe2 layers are metallic, with a Hall concentration of 1020 to 1023 cm–3, depending on the growth conditions.

Layer-Structured Anisotropic Metal Chalcogenides: Recent Advances in Synthesis, Modulation, and Applications

“…MC thin films prepared by CVD and MOCVD typically contain a high density of structural defects, impurities, and a large degree of spatial and electronic variability across the same sample. − Molecular beam epitaxy is a state-of-the-art ultrahigh vacuum (UHV) technique, which uses a high-purity elemental source and ultralow anisotropic growth rate, which enables accurate thickness control by adjusting the molecular beam flux and growth temperature. − By coupling the vapor–solid growth mechanism and epitaxy, the MBE process can produce clean-surface thin films that are suitable for investigating fundamental physical properties and electronic structures. − MBE-grown MCs on the vdW substrates (e.g., graphene, hBN) have been of superior quality than those grown on the non-vdW substrates (Al 2 O 3 , mica, 111-GaAs, Cu, Pt, Si, etc. ). , For the conventional heteroepitaxial growth mechanism, the same lattice symmetry and good lattice matching between the substrate and the epilayer are the prerequisite conditions. In the vdW epitaxy, those requirements can be greatly relaxed so that heteroepitaxial growth of 2D MCs is possible even under a different lattice symmetry and a large lattice mismatch as high as 50% (e.g., NbSe 2 on mica). , It is because the weak vdW interaction between the materials does not induce strain or misfit dislocations and allows the rotational alignment of the epilayer. , In the non-vdW epitaxy, the strong chemical interaction between the substrate and epilayer limits the mobility of adatoms and increases the nucleation rates. ,, MBE growth of MCs has been mainly focused on Se and Te compounds due to their low vapor pressure, except for a few cases. , Apart from numerous recent reports of 2D MCs, growth of several 1D MCs has also been reported recently.…”

“…568−573 MBE-grown MCs on the vdW substrates (e.g., graphene, hBN) 510 have been of superior quality than those grown on the non-vdW substrates (Al 2 O 3 , mica, 111-GaAs, Cu, Pt, Si, etc.). 476,574 For the conventional heteroepitaxial growth mechanism, the same lattice symmetry and good lattice matching between the substrate and the epilayer are the prerequisite conditions. In the vdW epitaxy, those requirements can be greatly relaxed so that heteroepitaxial growth of 2D MCs is possible even under a different lattice symmetry and a large lattice mismatch as high as 50% (e.g., NbSe 2 on mica).…”

Comparative coherence between layered and traditional semiconductors: unique opportunities for heterogeneous integration

“…(h) MBE NiTe 2 on GaAs. Reprinted with permission from [298]. Copyright (2021) American Chemical Society.…”

Charge Transfer Modulation in Vanadium‐Doped WS2/Bi2O2Se Heterostructures

“…[5] One can tune the thickness of these 2D components involved in 2D heterostructure structures to cover nearto mid-infrared spectral range with strong light-matter interactions. [6] On the contrary, such flexibilities cannot be imagined in conventional 2D heterostructures due to limitations in expensive growth techniques such as molecular beam epitaxy, [7,8] and metal-organic chemical vapor deposition (MOCVD) etc. [9] To realize the aforementioned 2D heterostructures transition metal dichalcogenides (TMDCs) have already shown great potential exhibiting interesting physical properties.…”