Misorientation-angle-dependent electrical transport across molybdenum disulfide grain boundaries

Abstract

Grain boundaries in monolayer transition metal dichalcogenides have unique atomic defect structures and band dispersion relations that depend on the inter-domain misorientation angle. Here, we explore misorientation angle-dependent electrical transport at grain boundaries in monolayer MoS2 by correlating the atomic defect structures of measured devices analysed with transmission electron microscopy and first-principles calculations. Transmission electron microscopy indicates that grain boundaries are primarily composed of 5–7 dislocation cores with periodicity and additional complex defects formed at high angles, obeying the classical low-angle theory for angles <22°. The inter-domain mobility is minimized for angles <9° and increases nonlinearly by two orders of magnitude before saturating at ∼16 cm2 V−1 s−1 around misorientation angle≈20°. This trend is explained via grain-boundary electrostatic barriers estimated from density functional calculations and experimental tunnelling barrier heights, which are ≈0.5 eV at low angles and ≈0.15 eV at high angles (≥20°).

Dynamical observations on the crack tip zone and stress corrosion of two-dimensional MoS2

“…The monolayer MoS 2 samples were grown on sapphire using chemical vapour deposition20, and then transferred to TEM grids using the polymethyl methacrylate (PMMA) method as a free-standing sheet21. Excellent quality of the as-grown MoS 2 crystal was confirmed by TEM (Supplementary Fig.…”

Degradation behaviors and mechanisms of MoS2 crystals relevant to bioabsorbable electronics

“…Because of the hexagonal atomic structure of semiconducting MoS 2 in the 2H phase, the misorientation angle ranges from 0°to 60°3 3,36 . The atomic defect structures in MoS 2 grains and GBs greatly affect the mechanical, electrical, and optoelectronic properties of MoS 2 -based devices 35,[37][38][39][40][41][42][43] . To thoroughly explore the degradation behaviors of MoS 2 grains and GBs with different inter-grain misorientation angles, we selected four samples with different angles and characterized their original morphologies and structures.…”

“…1g) 33 . Notably, the shape of GBs depends on the relative growth rates of the two adjacent edges, which are not easily distinguished in SHG images when the misorientation angle approaches 0°or 60°because of the 60°p eriodicity caused by the six-fold rotational symmetry of the MoS 2 lattice [33][34][35] . As demonstrated later, such a simple method of confirming the GBs enables the analysis of degradation processes.…”

Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures

“…As an example, the CVD deposition of MoS 2 on a commonly used SiO 2 /Si substrate typically results in the formation of a 2D polycrystalline material, composed by several domains with a triangular shape separated by GBs [77]. The structural and electrical properties of GBs have been the object of many experimental and theoretical investigations in the last years [78,79], due to their impact on the mobility of MoS 2 field effect transistors and their role in peculiar extrinsic charge transport phenomena in MoS 2 [80,81]. Recent investigations indicated that inter-domains scattering (due to GBs) can play a major role (as compared to the intra-domain scattering due to localized defects [68,82,83]) in the degradation of the MoS 2 mobility, especially for certain misorientation angles between MoS 2 domains [81].…”

“…The structural and electrical properties of GBs have been the object of many experimental and theoretical investigations in the last years [78,79], due to their impact on the mobility of MoS 2 field effect transistors and their role in peculiar extrinsic charge transport phenomena in MoS 2 [80,81]. Recent investigations indicated that inter-domains scattering (due to GBs) can play a major role (as compared to the intra-domain scattering due to localized defects [68,82,83]) in the degradation of the MoS 2 mobility, especially for certain misorientation angles between MoS 2 domains [81]. To this purpose, complex transistors structures and modeling for electrical data interpretation have been employed to evaluate the impact of the specific GB configurations on the MoS 2 channel mobility [81].…”