engleski

Sulphur concentration influence on morphology and optical properties of MoS2 monolayers

MoS2 in its two-dimensional (2D) form is one of the most studied materials in the last decade due to its promising applications in semiconducting industry (photosensors [1], optoelectronics [2], photovoltaics [2] etc.). One of the main approaches in synthesis of semiconducting 2D materials is chemical vapour deposition (CVD) technique. In this work we have systematically investigated how synthesis parameters (growth temperature TG, sulphur tempertaure TS and carrier gas flow) influence sample quality. As a result, correlation between synthesis parameters and samples morphology and optical response were obtained. By changing mentioned synthesis parameters the Mo:S ratio was consistently tuned which, in turn, modified both morphology and optical response of the sample. As the ratio is approaching to the ideal value of 1:2, the morphology of samples becomes more symmetric, triangular with even edges while the PL and Raman spectra intensities for given sample increase. If the sulphur concentration is increased compared to the ideal stoichiometric ratio, the samples become dendritic with uneven edges and optical response is poor. On the other hand, if the molybdenum concentration is increased by increasing TG, vertical growth is preferred rather than lateral, and bilayers or multiple- layered islands are formed. Complementary structural characterization by atomic force microscope (AFM) and scanning electron microscope (SEM) were used to determine existence of grain boundaries and cracks in crystal basal plane, showing that optimisation of synthesis parameters leads to high- quality crystal morphology. Our further work will focus on exploring the optical properties of crystals in low-temperature limit.

MoS2, Chemical vapor deposition (CVD), Growth parameters

nije evidentirano