Coverage-dependent differential reflectance spectra of MoS2 atomic films synthesized by CVD using a large-diameter quartz tube

Abstract

Here, we synthesized monolayer MoS2 under atmospheric pressure by chemical vapor deposition (CVD) using a quartz tube with a large-diameter up to 100 mm. The morphology of MoS2 thin films along the airflow direction was initially observed by the optical microscope. Raman spectra and atomic force microscopy (AFM) were utilized to characterize the thickness of samples. Moreover, the optical properties of four regions with continuous different coverage were systematically investigated by differential reflectance spectroscopy (DRS). It is found that MoS2 thin films in the sub-monolayer structure have exhibited the same energy positions of optical characteristic peaks, including A exciton peak at 1.91 eV, B exciton peak at 2.08 eV and C exciton peak at 2.84 eV. And the DRS shows that the intensity of B exciton peak rises at the rate of ~0.46 monolay−1 (ML−1). These results provide an insight for monitoring the growth and evolutions of MoS2 thin films with different coverage.