Fluctuation imaging of disorder in monolayer semiconductors

TL;DR

This paper introduces a super-resolution fluorescence fluctuation microscopy technique to image and analyze disorder in monolayer semiconductors, providing a faster, easier method to evaluate material quality and stability for nano-optoelectronic applications.

Contribution

The study adapts fluorescence fluctuation microscopy for imaging exciton disorder in monolayer semiconductors, offering a novel, non-invasive approach comparable to atomic force microscopy.

Findings

Fluctuation imaging detects disorder similar to AFM and hyperspectral imaging.

Thermal annealing reduces exciton fluctuations, indicating decreased disorder.

Method is faster and easier to implement than traditional imaging techniques.

Abstract

Monolayer semiconductors hold great potential for nanoscale electronics, optoelectronics, and photonics. Excitons dominate their optical properties. As their electric fields extend outside the monolayer, they are sensitive to their surroundings. Thus, disorder can cause exciton instability, which is detrimental to device performance and critical for scalability and reproducibility. Here, we adapt a super-resolution fluorescence fluctuation microscopy technique to image localized exciton fluctuations in monolayer semiconductors, allowing us to identify unstable spots in an otherwise continuous monolayer with constant fluorescence. These spots correspond to interfacial disorder measured by atomic force microscopy. We examine how different material interfaces influence the fluctuations by comparing several substrates and provide additional insight into the disorder behind the fluctuations using hyperspectral imaging. We also assess the reduction of disorder upon thermal annealing, evidenced by a decrease in fluctuations. Our results show that fluorescence fluctuation imaging can detect disorder features similar to those of atomic force microscopy and hyperspectral imaging, while being faster and easier to implement. Therefore, it is a promising method for evaluating the quality of monolayer semiconductors, particularly when integrated with nanostructures and heterostructures found in nano-optoelectronic devices.