ScholarWorks@숙명여자대학교

초록

Recently, a time-varying doping property from p-type to n-type was demonstrated for fresh exfoliated natural 2H-MoS2, and its origin was attributed to the out-diffused carbon from the bulk. We present density-functional theory calculations on C interstitial defects in a bilayer 2H-MoS2. Based on the energetic stability and the relevance to the out-diffusion process, we focus on three C interstitials: (i) the most stable at the surface bridge site, (ii) the second most stable at the surface tetrahedral site, and (iii) the one within the van der Waals (vdW) gap. Their fully relaxed structures are featured respectively by (i) the formation of C-S dimer occupying the surface S site, (ii) the breakage of the three-fold rotation symmetry, and (iii) the linkage of the upper and lower monolayers across the vdW gap. Electronic structure analysis of energy bands and partial charge density, along with the simulated scanning tunneling microscopy (STM) images, demonstrates that each C interstitial exhibits distinct, bias-dependent STM images that can be addressed in terms of atomic geometry, defect states, orbital hybridization, and resonant states. These STM features provide a fingerprint of C interstitial defects, which will serve as a reference in identifying near-surface C defects of transition-metal dichalcogenides.

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