Abstract
Controlling the radiative properties of monolayer transition metal dichalcogenides is key to the development of atomically thin optoelectronic devices applicable to a wide range of industries. A common problem for exfoliated materials is the inherent disorder causing spatially varying nonradiative losses and therefore inhomogeneity. Here we demonstrate a five-fold reduction in the spatial inhomogeneity in monolayer WS2, resulting in enhanced overall photoluminescence emission and quality of WS2 flakes, by using an ambient-compatible laser illumination process. We propose a method to quantify spatial uniformity using statistics of spectral photoluminescence mapping. Analysis of the dynamic spectral changes shows that the enhancement is due to a spatially sensitive reduction of the charged exciton spectral weighting. The methods presented here are based on widely adopted instrumentation. They can be easily automated, making them ideal candidates for quality assessment of transition metal dichalcogenide materials, both in the laboratory and industrial environments.
Highlights
Controlling the radiative properties of monolayer transition metal dichalcogenides is key to the development of atomically thin optoelectronic devices applicable to a wide range of industries
Amongst methods to improve the homogeneity of exfoliated transition metal dichalcogenides (TMDs), the most wellknown are hexagonal boron nitride (h-BN) encapsulation and flake suspension[21]
Using spatially resolved photoluminescence spectroscopy to characterise monolayer WS2 exfoliated onto PDMS stamps, we demonstrate a statistical analysis approach to quantify spatial homogeneity and compare material quality
Summary
Controlling the radiative properties of monolayer transition metal dichalcogenides is key to the development of atomically thin optoelectronic devices applicable to a wide range of industries. The methods presented here are based on widely adopted instrumentation They can be automated, making them ideal candidates for quality assessment of transition metal dichalcogenide materials, both in the laboratory and industrial environments. Insufficient control of lattice d efects[8,13,14,15,16], the dielectric environment[17], and TMD-metal interface q uality[18,19] continues to limit the performance and reproducibility of fabricated devices[20] These deficiencies typically manifest as spatial and spectral inhomogeneity, accompanied by low photoluminescence yield. Amongst methods to improve the homogeneity of exfoliated TMDs (and graphene), the most wellknown are hexagonal boron nitride (h-BN) encapsulation and flake suspension[21] These transfer-based techniques have successfully led to demonstrations of high performance TMD-devices. The measurements and modelling presented here aim to complement previous r eports[33,34] that elucidate possible mechanisms of laser illumination induced spectral changes on monolayer TMDs
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