Controllable Thermal Oxidation and Photoluminescence Enhancement in Quasi-1D van der Waals ZrS₃ Flakes

Abstract

In this study, we report on the thermal oxidation of few-layer ZrS3 flakes as a function of temperature and heating time. We characterize the changes to the material crystal structure caused by the thermal treatment using atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and electrical transport measurements and link these results to the observed changes in optical contrast for on-substrate flakes. Importantly, we observe a very strong photoluminescence emission enhancement in the heated samples, with intensities comparable to those of direct-gap monolayer MoS2. We attribute this enhancement to mid-gap states in the thermally synthesized oxides of zirconium which form on the flake surface. We show that this emission is isotropic, unlike that of the untreated ZrS3, which unlocks an additional degree of freedom to the modulation of the optoelectronic properties of quasi-one-dimensional van der Waals materials.