Atomic-scale defects and electronic properties of a transferred synthesized MoS₂ monolayer

Abstract

MoS monolayer samples were synthesized on a SiO/Si wafer and transferred to Ir(111) for nano-scale characterization. The samples were extensively characterized during every step of the transfer process, and MoS on the final substrate was examined down to the atomic level by scanning tunneling microscopy (STM). The procedures conducted yielded high-quality monolayer MoS of milimeter-scale size with an average defect density of 2 × 10 cm. The lift-off from the growth substrate was followed by a release of the tensile strain, visible in a widening of the optical band gap measured by photoluminescence. Subsequent transfer to the Ir(111) surface led to a strong drop of this optical signal but without further shifts of characteristic peaks. The electronic band gap was measured by scanning tunneling spectroscopy (STS), revealing n-doping and lateral nano-scale variations. The combined use of STM imaging and density functional theory (DFT) calculations allows us to identify the most recurring point-like defects as S vacancies.

2D MoS2 Heterostructures on Epitaxial and Self‐Standing Graphene for Energy Storage: From Growth Mechanism to Application

“…The image shows a hexagonal pattern and the line profile over the red line allows to measurement of an atomic distance of 0.31 nm, in excellent agreement with the reported 2H phase MoS 2 unit cell of 3.1 Å. [ 53–55 ]…”

Transfer of large-scale two-dimensional semiconductors: challenges and developments

“…Such behavior was not observed in the PMMA-assisted transfer due to the strain dominating the peak shifts [110]. Other than impurities, different substrates [104], substrateborne moisture [79] and vacancy defects (such as sulfur) [77] can also lead to doping and thus change the A 1g peak.…”

“…Wrinkles, cracks, bubbles or polymer residues can be observed [77,79]. due to thermal fluctuations [73].…”

“…A related technique, known as scanning tunneling spectroscopy (STS), can also be used in the same set-up, providing information on the local electronic density of state of the material. The combination of both STM and STS was used by Delač Marion et al on transferred ML CVDgrown MoS 2 on Ir(111) [79]. A corrugation of the MoS 2 film was observed in the STM image, indicating a rippling of the 2D layer in a manner similar to the rippling of graphene on SiO 2 /Si (see figures 18(a) and (b)).…”

One-Dimensional Frenkel Chain Defects in CsBi4Te6

“…At the defect-free position (in Figures 2a and 2c), without having change in the arrangement of atoms, the DOS peak shifts toward positive energy after being kept at room temperature, which indicates the one-dimensional Frenkel defects donate electrons into the global sample. 28,29 Specifically, Figure 2a shows the STM image of the CsBi 4 Te 6 surface after being kept for 2.5 h, where the dark vacancy and bright interstitial are marked with white-dashed and blue-solid circles, respectively. Compared with Figure 1f, the dI/dV spectra acquired at the defect-free area in Figure 2b show an ∼20 meV E F shift toward positive energy, where P 1 and P 3 are located at −0.24 and 0.34 eV in Figure 1f, now locate at −0.26 and 0.32 eV in Figure 2b, respectively.…”