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Correction for 'Thickness-dependent in-plane thermal conductivity of suspended MoS2 grown by chemical vapor deposition' by Jung Jun Bae et al., Nanoscale, 2017, 9, 2541-2547.

Although many studies have been carried out on the doping of transition metal dichalcogenides (TMDCs), introducing controllable amounts of dopants into a TMD lattice is still insufficient. Here we demonstrate doping controlled TMDC growth by the replacement of selenium with phosphorus during the synthesis of the monolayer WSe2. The phosphorus doping density was precisely controlled by fine adjustment of the amount of P2O5 dopant powder along the pre-annealing time. Raman spectroscopy, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and high-angle annular bright field scanning tunneling electron microscopy (HAADF STEM) provide evidence that P doping occurs within the WSe2 crystal with P occupying the substitutional Se sites. With regard to its electrical characteristics, the hole majority current of P-doped WSe2 is 100-times higher than that of the intrinsic WSe2. The measured doping concentration ranged from ∼8.16 × 1010 to ∼1.20 × 1012 depending on the amount of P2O5 dopant powder by pre-annealing.

Direct current (DC) and low-frequency (LF) noise analyses of a chemical vapor deposition (CVD)-grown monolayer MoS2 field effect transistor (FET) indicate that time-varying carrier perturbations originate from gas adsorbates. The LF noise analysis supports that the natural desorption of physisorbed gas molecules, water and oxygen, largely reduces the interface trap density (NST) under vacuum conditions (∼10-8 Torr) for 2 weeks. After a longer period of 8 months under vacuum, the carrier scattering mechanism alters, in particular for the low carrier density (Nacc) region. A decrease of both NST and the scattering parameter αSC with desorption of surface adsorbates from MoS2, explains the enhanced carrier mobility and the early turn-on of the device. The stabilized carrier behavior is verified with γ = 0.5 in the formula αSC ∝ Nacc-γ, as in Si-MOSFETs. Our results support that the gas adsorbates work as charged impurities, rather than neutral ones.

The in-plane thermal conductivities of suspended monolayer, bilayer, and multilayer MoS 2 films were measured in vacuum by using non-invasive Raman spectroscopy. The samples were prepared by chemical vapor deposition (CVD) and transferred onto preformed cavities on a Au-coated SiO 2 /Si substrate. The measured thermal conductivity (13.3 ± 1.4 W m -1 K -1 ) of the suspended monolayer MoS 2 was below the previously reported value of 34.5 ± 4 W m -1 K -1 . We demonstrate that this discrepancy arises from the experimental conditions that differ from vacuum conditions and small absorbance. The measured in-plane thermal conductivity of the suspended MoS 2 films increased in proportion to the number of layers, reaching 43.4 ± 9.1 W m -1 K -1 for the multilayer MoS 2 , which explicitly follows the Fuchs-Sondheimer suppression function. The increase in the thermal conductivity with the number of MoS 2 layers is explained by the reduced phonon boundary scattering. We also observe that the Fuchs-Sondheimer model works for the thickness-dependent thermal conductivity of MoS 2 down to 10 nm in thickness at room temperature, yielding a phonon mean free path of 17 nm for bulk.

Structural defects can critically influence the electrical and optical properties of monolayered molybdenum disulfide (MoS2) grown by chemical vapor deposition (CVD); thus, convenient optical methods that can visualize grain boundaries (GBs) and other structural defects are in great demand. Although photoluminescence (PL) imaging can identify the presence of relatively large defects, the limited spatial resolution of PL imaging prevents the identification of nanosized structural defects in the monolayered MoS2. Additionally, the origin of the PL signal contrast observed at certain types of structural defects, such as GBs, is not yet understood. Here, we present near-field PL images of CVD-grown monolayered MoS2, collected to identify nanosized line defects and adlayer defects in the monolayered MoS2. Our results of correlated scanning electron microscopy imaging and the inspection of near-field PL profiles of line defects and GBs suggest that decreased PL on GBs is due to the local physical damage of the MoS2 film rather than due to the presence of localized states.