Towards Intrinsic Charge Transport in Monolayer Molybdenum Disulfide by Defect and Interface Engineering

Abstract: Molybdenum disulfide is considered as one of the most promising two-dimensional semiconductors for electronic and optoelectronic device applications. So far, the charge transport in monolayer molybdenum disulfide is dominated by extrinsic factors such as charged impurities, structural defects and traps, leading to much lower mobility than the intrinsic limit. Here, we develop a facile low-temperature thiol chemistry to repair the sulfur vacancies and improve the interface, resulting in significant reduction of the charged impurities and traps. High mobility greater than 80cm2 V-1 s-1 is achieved in backgated monolayer molybdenum disulfide field-effect transistors at room temperature. Furthermore, we develop a theoretical model to quantitatively extract the key microscopic quantities that control the transistor performances, including the density of charged impurities, short-range defects and traps. Our combined experimental and theoretical study provides a clear path towards intrinsic charge transport in two-dimensional dichalcogenides for future high-performance device applications.

• The paper demonstrates that MPS treatment repairs sulfur vacancies, doubling room-temperature mobility in MoS₂ FETs.
• It employs a robust theoretical model to quantify the impact of impurities and defects on charge transport.
• The findings pave the way for high-performance MoS₂ devices by achieving near-intrinsic charge transport through defect engineering.

Intrinsic Charge Transport Enhancement in Monolayer MoS₂ through Defect and Interface Engineering

This research paper investigates the charge transport limitations in monolayer molybdenum disulfide (MoS₂), a two-dimensional material with significant potential in electronic and optoelectronic applications. The study identifies extrinsic factors, particularly sulfur vacancies (SVs) and charged impurities, as major impediments to achieving the intrinsic charge transport limits in MoS₂. The authors propose a low-temperature thiol chemistry method using (3-mercaptopropyl)trimethoxysilane (MPS) to repair SVs, significantly improving the mobility of MoS₂ field-effect transistors (FETs).

Key Findings

The research achieves a notable mobility of 80 cm²/Vs at room temperature in backgated FETs treated with MPS, significantly surpassing the typical mobility values of untreated samples (~40 cm²/Vs at room temperature). At low temperatures, mobility exceeds 300 cm²/Vs, marking an enhancement that suggests near-intrinsic transport conditions. The paper's insights extend to electrical transport characteristics, demonstrating reduced impurity scattering and improved sample interface quality attributable to the MPS treatment.

Theoretical Model and Transport Analysis

The study presents a theoretical model to quantify the major contributors to charge transport limitation: charged impurities, short-range defects, and localized charge traps. Through this model, key microscopic quantities—such as the density of these defects—are extracted by fitting the experimental data. The model considers Matthiessen's rule to integrate various scattering mechanisms, providing a comprehensive understanding of charge transport in MoS₂.

Implications of Findings

The implications of this work are twofold. Practically, the repair of SVs using MPS treatment opens a pathway to fabriate high-performance MoS₂ devices with transport properties approaching intrinsic limits. Theoretically, the research contributes to a nuanced understanding of defect and interface engineering in two-dimensional materials, offering insights relevant to other transition metal dichalcogenides.

Future Developments and Research Directions

The results point to the necessity of further optimizing both the intrinsic material quality and the surrounding interface to fully exploit the potential of MoS₂ in electronic applications. Future research is suggested to refine the engineering strategies that could eliminate residual extrinsic factors, potentially through advanced chemical treatments or heterostructure integration. Investigations into the transferability of these techniques to other 2D materials could also benefit the broader field of nanoscale semiconductor devices.

Overall, the paper presents a robust approach to confronting the challenges in charge transport for MoS₂, providing a significant step towards realizing its potential in future electronic and optoelectronic devices.