Abstract
In present study, we develop an effective and universal technique for retrieving dispersion of bulk and monolayer TMDs from spectroscopic ellipsometry measurements. The basis of the method is excitonic nature of the dispersion. In addition, we demonstrate beneficial influence of annealing on optical properties of MoS2.
Highlights
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently become the focus of many research works due to their outstanding electrical and optical properties[1,2]̵, which make them suitable for a variety of different applications[1]̵
This occurs because of sensitivity of physical properties of TMDs to surroundings[17]̵, defects[18] and synthesis method[19]̵. It is not clear which data should be used for calculation of theoretical performance of the devices based on TMDs. To solve this problem we propose a universal algorithm for optical constants determination of 2D TMDs using spectroscopic ellipsometry (SE) and demonstrate it on the example of Chemical Vapor Deposition (CVD)-grown MoS2̵, MoSe2̵̵, WS2̵ and WSe2̵ as the most commonly used among others[1]̵
Suggested algorithm could be applied without changing to any TMDs with the excitonic nature of dispersion
Summary
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently become the focus of many research works due to their outstanding electrical and optical properties[1,2]̵, which make them suitable for a variety of different applications[1]̵ These materials have been already successfully used as a building block for solar cells[3]̵, transistors[4]̵, sensors[5]̵, light emitters[6̵], transparent and conductive electrodes[7] and lasers[8]̵, demonstrating the performance even higher than devices based on graphene[9]̵. Obtained results show similar behavior for dielectric function, the absolute values of ε1 and ε2 differs a lot (within 50 %) This occurs because of sensitivity of physical properties of TMDs to surroundings[17]̵, defects[18] and synthesis method[19]̵. We show that annealing helps to increase absorption for A and B-excitons due to reducing contaminations such as water which could be useful for improving performance of photodetectors and solar cells [̵9]̵
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