High-Throughput Optical Identification and Statistical Analysis of Atomically Thin Semiconductors

Abstract

Transition metal dichalcogenides (TMDs) are layered two-dimensional semiconductors explored for optoelectronic applications, ranging from light-emitting diodes to single-photon emitters. Such devices require monolayer TMDs, typically obtained through mechanical exfoliation followed by manual identification with a brightfield optical microscope. While this procedure provides high-quality crystals, the identification is time-intensive, low-throughput, and prone to human error, which significantly limits TMD research. Here, we report a simple and fully automated approach for high-throughput identification of TMD monolayers using photoluminescence microscopy. We demonstrate the identification of up to three monolayers per second, offering a 10000x efficiency increase compared to conventional search and verification is demonstrated. This ability allows us to measure geometric and photoluminescence-intensity features of more than 2400 monolayers and bilayers of WSe2, MoSe2, and MoS2. Due to these large numbers, we can study and quantify material properties previously inaccessible. For example, we show that the mean photoluminescence intensity from a monolayer correlates with its size due to reduced emission from its edges. Further, we observe large variations in brightness (up to 10x) from WSe2 monolayers of different batches produced by the same supplier. Therefore, our approach not only increases fabrication efficiency but also enhances sample quality for optoelectronic devices of atomically thin semiconductors.