Abstract
Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. Although several monolayer-based photodetectors have been demonstrated, single-layered optical memory devices suitable for high-quality image sensing have received little attention. Here we report a concept for monolayer MoS2 optoelectronic memory devices using artificially-structured charge trap layers through the functionalization of the monolayer/dielectric interfaces, leading to localized electronic states that serve as a basis for electrically-induced charge trapping and optically-mediated charge release. Our devices exhibit excellent photo-responsive memory characteristics with a large linear dynamic range of ∼4,700 (73.4 dB) coupled with a low OFF-state current (<4 pA), and a long storage lifetime of over 104 s. In addition, the multi-level detection of up to 8 optical states is successfully demonstrated. These results represent a significant step toward the development of future monolayer optoelectronic memory devices.
Highlights
Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions
On the basis of the ON/OFF ratio of the readout charge as shown in Fig. 2c, we found that the linear dynamic range (LDR), which represents the ratio of the full-well charge capacity to the dark readout charge within the linear region, was found to be
The information can be stored and retrieved while maintaining a high ON/OFF ratio greater than 100 even after waiting for 104 s, consuming ultra-low power without a source-drain bias (Fig. 2f). These results indicate that our optical memory device with a long-term storage lifetime could have, fundamentally, great potential for the development of much simpler image sensing chip architecture without the additional non-volatile memory arrays required for charge storage
Summary
Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. MoS2 undergoes a transition from an indirect to direct bandgap when the thickness is reduced to a monolayer (B0.7 nm), which is accompanied by a dramatic enhancement of the photoluminescence (PL) efficiency and strong light-matter interactions[3,6,7] due to the quantum confinement that occurs in layered d-electron materials[8] These attractive features of monolayer TMDC make it a promising material for novel flexible and wearable optoelectronics[9,10,11] as well as novel electronic devices[12,13,14,15]. We show a new class of MoS2 monolayer optoelectronic memory devices based on charge trapping at the MoS2/SiO2 dielectric interface along with the subsequent optically-induced charge release, which allows for a high ON/OFF ratio with a linear response to the optical dose, and a long retention time
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