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arXiv2026

Toward two dimensional MoS2 electrets

Here, we show that controlled sulfur vacancy engineering converts monolayer MoS2 into an electret, imparting the ability to store quasi-permanent electrostatic charge within a single atomic layer. Sulfur vacancies are generated with submicrometer spatial control by stamp-assisted electrode-free electrochemical nanolithography, yielding programmable defect densities from 10 10 to 10 13 1 cm-2. The resulting vacancy domains act as deep electron traps and produce surface charge densities up to 1 uCcm-2, with charge retention in the order of hundreds days under ambient conditions. Kelvin probe and electric force microscopies directly reveal stable electrostatic patterns that replicate the lithographic motif. The same vacancy landscape simultaneously defines exciton-quenching regions, generating co-localized optical and electrostatic contrast and reducing the apparent exciton lifetime from 15 ns to 180 ps through enhanced nonradiative recombination. The persistence of the optical response over one year identifies sulfur vacancies, rather than transient charge states, as the origin of the patterned functionality. These results establish defect-engineered MoS2 as the first two-dimensional electret and demonstrate that atomic vacancies can be exploited as functional elements for encoding electrostatic and excitonic behavior in a single atomic layer.

cond-mat.mtrl-sci↗

arXiv2023

Synthesis of built-in highly strained monolayer MoS2 using liquid precursor chemical vapor deposition

Strain engineering is an efficient tool to tune and tailor the electrical and optical properties of 2D materials. The built-in strain can be tuned during the synthesis process of a two dimensional semiconductor, as molybdenum disulfide, by employing different growth substrate with peculiar thermal properties. In this work we demonstrate that the built-in strain of MoS2 monolayers, grown on SiO2/Si substrate using liquid precursors chemical vapor deposition, is mainly dominated by the size of the monolayer. In fact, we identify a critical size equal to 20 um, from which the built-in strain increases drastically. The built-in strain is maximized for 60 um sized monolayer, leading to 1.2% tensile strain with a partial release of strain close to the monolayer triangular vertexes due to formation of nanocracks. These findings also imply that the standard method for evaluation of the number of layers based on the Raman modes separation becomes unreliable for monolayer with a lateral size above 20 um.

cond-mat.mtrl-sci↗