Unique Morphologies of Molybdenum Disulphide: Sheets, Diffusion Limited Cluster Aggregates and Fractals, by Langmuir- Blodgett Assembly for Advanced Electronics

TL;DR

This paper explores the self-assembly of exfoliated MoS2 flakes into various morphologies using Langmuir-Blodgett technique, revealing new excitonic features and demonstrating potential for advanced electronic device fabrication.

Contribution

It introduces a novel method for depositing MoS2 flakes into diverse structures and uncovers a new exciton, advancing the understanding of MoS2 assembly and optoelectronic properties.

Findings

MoS2 flakes form diffusion-limited cluster aggregates and fractals.

A new exciton at 2.43 eV was observed in LB assembled MoS2.

FETs fabricated show a mobility of 7.4 cm²V⁻¹s⁻¹ and on-off ratio of 10^5.

Abstract

A plethora of different morphologies are fabricated by the self assembly of molybdenum disulphide (MoS2) exfoliated flakes with the help of Langmuir-Blodgett (LB) technique at the liquid/air interface. The MoS2 flakes are chemically exfoliated in various solvents but their stable sheet like assembly on substrate is achieved only in case of the flakes exfoliated in dimethylformamide. The density of the monolayer sheets is finely controlled by the surface pressure while the stabilization of MoS2 LB film onto the water subphase results in its self assembly into diffusion limited cluster aggregates and fractals. We further demonstrate the effect of excitation on the emission of LB assembled MoS2 sheets which reveals the existence of a new exciton corresponding to 2.43 eV apart from the direct bandgap emission at 1.86 eV. Finally, field effect transistors are fabricated on SiO2/Si and a mobility of 7.4 cm2V-1s-1 with a current on-off ratio of 10^5 is obtained. This work provides a new approach for the systematic deposition of the solution processed exfoliated flakes on large scale as well as formation of pattern structures in a natural way.