Characterization of Rotational Stacking Layers in Large-Area MoSe₂ Film Grown by Molecular Beam Epitaxy and Interaction with Photon

Abstract

Transition metal dichalcogenides (TMDCs) are promising next-generation materials for optoelectronic devices because, at subnanometer thicknesses, they have a transparency, flexibility, and band gap in the near-infrared to visible light range. In this study, we examined continuous, large-area MoSe film, grown by molecular beam epitaxy on an amorphous SiO/Si substrate, which facilitated direct device fabrication without exfoliation. Spectroscopic measurements were implemented to verify the formation of a homogeneous MoSe film by performing mapping on the micrometer scale and measurements at multiple positions. The crystalline structure of the film showed hexagonal (2H) rotationally stacked layers. The local strain at the grain boundaries was mapped using a geometric phase analysis, which showed a higher strain for a 30° twist angle compared to a 13° angle. Furthermore, the photon-matter interaction for the rotational stacking structures was investigated as a function of the number of layers using spectroscopic ellipsometry. The optical band gap for the grown MoSe was in the near-infrared range, 1.24-1.39 eV. As the film thickness increased, the band gap energy decreased. The atomically controlled thin MoSe showed promise for application to nanoelectronics, photodetectors, light emitting diodes, and valleytronics.

Molecular Beam Epitaxy of Highly Crystalline MoSe2 on Hexagonal Boron Nitride

“…The extracted mobility is more than 2 orders of magnitude higher than previously reported MBE-grown MoSe 2 on GaAs(111) and is comparable to CVD-grown samples with values ranging from 0.02 to 95 cm 2 /(V s) (Table ). It is noted that most of the previously reported MBE growth studies rarely report on charge transport properties. ,,− …”

“…Molecular beam epitaxy (MBE) provides high precision in the control of growth temperature and precursor flux, as well as the use of a contaminant-free environment. The MBE of MoSe 2 has been demonstrated to produce high quality growth on metallic substrates, which enabled fundamental studies of 2D-TMDC system. ,, However, the electrical performance of MBE grown samples are rarely reported. ,,− Thus far, MBE-grown MoSe 2 on GaAs(111) substrate exhibits mobility values of <1 cm 2 /(V s), and on sapphire substrates, the grown films are insulating , (Table ). This indicates that the choice of substrate can drastically affect the electrical performance of MBE-grown film.…”

Quasicrystalline electronic states in 30∘ rotated twisted bilayer graphene

“…In addition, similar TBGs have been realized on top of Ni surface 17,18 and also by a transfer method 19 . Moreover, another 30 • -rotated stack of atomic layers have also been realized in graphene on top of BN layer 20 as well as MoSe 2 bilayer system 21 . In such the quasicrystalline TBG (QC-TBG), the moiré effective approach sketched above breaks down because its main assumption that the moiré pattern governs the system is no longer valid.…”

TMDs beyond MoS2 for Electrochemical Energy Storage

“…HRTEM images of MoSe 2 (a‐ii), WS 2 (b‐ii), MoTe 2 (c‐ii), and WSe 2 (d‐ii), demonstrating the characteristic lattice fringes. (a‐ii) Adapted with permission from Ref ; Copyright 2017, American Chemical Society. (b‐ii) Adapted with permission from Ref.…”