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Band bending near mirror twin domain boundaries (MTBs) in a MoSe2 monolayer grown on different substrates, i.e., highly oriented pyrolytic graphite (HOPG), graphene‐on‐SiC, and crystalline Au(110), is investigated by low temperature scanning tunneling microscopy/spectroscopy. Upshift bending of the valence band edge near MTB is observed on both graphene and HOPG substrates, whereas a downshift bending is found on Au(110). For the former, the magnitudes of bending are different. This is explained based on the static charge model, where an accumulative charge exists at MTBs due to both the electrical dipole discontinuity across the MTB as well as charge transfer between the substrate and MoSe2 epilayer. The relevance of the static electric model is further affirmed by noting a geometric effect on the band bending, where it is asymmetric across the vertex of an MTB loop. [ABSTRACT FROM AUTHOR]

Monolayer (ML) transition-metal dichalcogenides (TMDs) have attracted a lot of research interest in recent years due to their many interesting properties as well as their application promises. Depending on the specific combinations of metals (e.g., Mo and W) with chalcogen elements (e.g., S, Se, and Te), binary TMDs exhibit a wide spectrum of physical characteristics, e.g., from metal to semiconductor and/or superconductor. Extension from binary to ternary compounds and alloys may offer even wider variations of properties and are thus of interest from both fundamental and practical points of view. In this work, we substitute Mo for niobium (Nb) and rhenium (Re) in ML MoSe2 during molecular-beam epitaxy and probe their effects on structural and electrical properties. We find that low-concentration Nb and Re in ML-MoSe2 are both shallow dopants, with Re being an electron donor and Nb acceptor, respectively. By changing Nb(Re)/Mo flux ratios, we can effectively tune the Fermi level by varying electron or hole concentrations in MoSe2. On the other hand, both Nb and Re are found to cause mirror-twin domain boundary defects to proliferate in MoSe2. [ABSTRACT FROM AUTHOR]

Monolayer Doping: A Shallow Acceptor of Phosphorous Doped in MoSe2 Monolayer (Adv. Phosphorous doping in a MoSe SB 2 sb monolayer is achieved by co-deposition of P, Se, and Mo during molecular-beam epitaxy, as reported by Maohai Xie and co-workers in article number 1900830. P atoms substitute Se in MoSe SB 2 sb , acting as acceptors and causing a Fermi-level shift. [Extracted from the article]

Tuning the conductivity and other electronic properties by doping in ultrathin layers of transition‐metal dichalcogenides is of great scientific and practical interest. As with traditional semiconductors, controllable doping is essential for device applications of the materials. Here, hole doping in epitaxial MoSe2 by phosphorus (P) are reported, where substitutional P at the Se sites acts as a shallow acceptor. P substituting Se in MoSe2 is identified by annular dark field scanning transmission electron microscopy, Auger electron spectroscopy, and X‐ray photoelectron spectroscopy. Scanning tunneling spectroscopy and ultraviolet photoemission spectroscopy reveal in‐gap defect states and Fermi‐level shifts, suggesting the hole doping effect of substitutional P. Combining with density functional theory calculation and partial charge analysis, the binding energies of impurity levels of group V elements in a MoSe2 monolayer are elucidated, where the dopant energy level becomes shallower with increasing atomic mass. [ABSTRACT FROM AUTHOR]

A mirror twin-domain boundary (MTB) in monolayer MoSe 2 represents a (quasi) one-dimensional metallic system. Its electronic properties, particularly the low-energy excitations in the so-called 4|4P-type MTB, have drawn considerable research attention. Reports of quantum well states, charge density waves, and the Tomonaga-Luttinger liquid (TLL) have all been made. Here, by controlling the lengths of the MTBs and employing different substrates, we reveal by low-temperature scanning tunneling microscopy/spectroscopy, Friedel oscillations and quantum confinement effects causing the charge density modulations along the defect. The results are inconsistent with charge density waves. Interestingly, for graphene-supported samples, TLL in the MTBs is suggested, whereas that grown on gold, an ordinary Fermi liquid, is indicated.

Confining interacting particles in one-dimension (1D) changes the electronic behavior of the system fundamentally, which has been studied extensively in the past. Examples of 1D metallic systems include carbon nanotubes, quasi-1D organic conductors, metal chains, and domain boundary defects in monolayer thick transition-metal dichalcogenides such as MoSe 2 . Here single and bundles of Mo 6 Se 6 nanowires were fabricated through annealing a MoSe 2 monolayer grown by molecular-beam epitaxy on graphene. Conversion from two-dimensional (2D) MoSe 2 film to 1D Mo 6 Se 6 nanowire is reversible. Mo 6 Se 6 nanowires form preferentially at the Se-terminated zigzag edges of MoSe 2 and stitch to it via two distinct atomic configurations. The Mo 6 Se 6 wire is metallic and its length is tunable, which represents one of few 1D systems that exhibit properties pertinent to quantum confined Tomonaga-Luttinger liquid, as evidenced by scanning tunneling microscopic and spectroscopic studies.